85 BRAT no start/run issue

[mhisstc]

I think I'm having a problem with my 100% stock '85 BRAT related to the ignition control module.  In order to effectively trouble shoot this, I'm going to include all of the background information and trouble shooting I've already done along with my speculations, so this may get a bit long.

 

My father-in-laws BRAT sat for 15-20 years before my daughter decided she wanted to get it running again and drive it to high school as her first car.

 

So as part of a general clean-up and maintenance catch-up, I completely cleaned out the fuel system including all of the rust and varnish in the fuel tank, installed a new fuel pump, filters, new hoses out back around the pump and tank, and tore apart and cleaned out the Hitachi carb.  I also went completely through the vacuum and ignition systems diagrams to verify vacuum hose and ignition system wire routing and connections, replaced a couple of the vacuum hoses, and checked all of the specs of all of the ignition system components. This included verifying the Ohms value of the coil primary and secondary and the Ohms value of the ignition control module (a.k.a. trigger coil or signal generator).  According to the Chilton's manual, the coil primary should be 0.84-1.02 Ohms and the secondary should be 8.5-1.02 kilo-Ohms.  It also indicates a reluctor gap of 0.012-0.016" or 0.3-0.4mm with a resistance value of 130-190 Ohms on the signal generator (ignition control module).  I found out the polarity of the multimeter matters when checking the Ohms of the ignition control module.  I don't understand why, but I found one way would give me a valid reading while the other way would read infinity like an open circuit instead.

 

Anyway, once everything was cleaned and checked over, I was happy it ran even though it was still a little bit "sputtery".  I continued to drive it to verify everything worked before I handed it over to my daughter.  As I drove it for a couple of days like that, I thought maybe the fuel system wasn't as clean as it could have been and the carb needed cleaned again.  But as luck would have it, it failed to start at all one day in a store parking lot. There was no sound from the fuel pump, so I was worried the fuel pump control unit may have gone bad.  I towed it back home to trouble shoot it and figured out by going through all the same things I went through previously that the ignition control module (trigger coil/signal generator) was showing a resistance value of infinity.  It looked like that module went bad.  As I inspected it, I also saw wear marks on the module from the reluctor rubbing on it and it also looked like the reluctor may have also been hitting the stator.  That's when I took a closer look at the distributor shaft play.  It was bad, and the general condition of the distributor internals was looking sketchy.  I also don't think the vacuum advance was working.  When I looked up ignition components on the Rock Auto site, I found just the ignition module for the Hitachi distributor was $93 while the whole distributor including the module and vacuum advance was $116.  It was a no-brainer to take care of it all with a new distributor.

 

When the new distributor arrived, I indexed everything on the old one, pulled it out, popped the new one in, and it ran like a champ.  Shortly after I installed the new distributor, I noticed my voltage gauge was showing values that were too high at higher RPM and too low at lower RPM.  I'm not sure if this was going on when the original distributor was still installed.  It appeared the voltage regulator was bad in the alternator.  Once I replaced the alternator, my voltage was rock solid where it should be.  It ran great for about another week, then it failed to start on me again just like it had done previously.  There was no sound from the fuel pump.  Again I feared it was the fuel pump control unit, but when I checked the ignition control module, I got infinity resistance again, so it appeared the module went bad in the new distributor.  I never verified the initial Ohm value of the ignition control module in the new distributor was within tolerance according to the Chilton's manual before I installed it, but it ran great while it was running.  It was pretty clear the previously "sputtery" engine was due to a sloppy old distributor.

 

So figuring I got a new distributor with a bad module, I warrantied it back to Rock Auto and ordered a new distributor. I also wondered if maybe the bad voltage regulator and the resulting high and low voltages had something to do with the original ignition module and new ignition module in the new distributor failing. I still had the old original coil installed even though I verified it as being good, but I went ahead and installed a new coil to remove that as a possible future failure point.  I did verify the new coil met specs on the primary and secondary before I installed it.  So when the new distributor arrived, I indexed everything again, and installed the second new distributor.  Nothing changed.  I got no sound from the fuel pump, and the engine didn't run.  Figuring there was no way the module was bad in my second new distributor, and that it may be the fuel pump control unit, I poured a little fuel in the carb and it still didn't run.  So then I checked the Ohm value on the module.  It was NOT in spec within the 130-190 Ohm value specified in the Chilton's manual.  It was more like 820 Ohms.  Crap, does this mean I got a new distributor with another bad module?  I really didn't want to warranty a second new distributor.  That's when I found I could order an ignition module from OReiley's for $20.  They also had one for $92, but I went ahead and got the $20 one as they were both listed for use in the BRATs Hitachi distributor.  There was no difference stated between the two on the web site, and the store personnel couldn't tell me what the difference was between the $20 unit and the $92 unit either, other than brand and price.

 

I got the new ignition module from OReily's today.  Before I installed it, I checked the resistance value.  It was around 830 Ohms.  Uh Oh.  That's NOT in the range Chilton's says it should be, and it's nearly the same as the one I'm going to be replacing.  So I went ahead and replaced the module.  Same problem.  No fuel pump noise, and no run.  Crap.

 

What I suspect is there IS some kind of difference between ignition modules that otherwise appear identical and are listed as working in the Hitachi distributor that is causing the resistance within the module to be out of tolerance for the system.

 

Is it possible that an ignition control module resistance value much higher than it should be could be read as being an open circuit by the fuel pump control module?  In that condition, is the fuel pump control module preventing the fuel pump from running to prime the carb when moving the key from the Off to On position, and is it also preventing a spark signal from being generated, which would also prevent the coil from firing and prevent the fuel pump from running while the engine is cranking?

 

I know if I have the key in the On position, and I remove either the + or - ignition power leads to the coil, my fuel pump will run as it should to prime the carb as if I had turned the key from Off to On.  The same things happens if I leave the key in the On position and I pull the coil fuse, or I unplug/replug in the Fuel Pump Control Unit located on the kick panel above the hood latch pull handle.  The fuel pump runs to prime the carb, but the pump will not run when cranking and there is no spark to fire the engine.

 

To me, this says my issue is the ignition control module sending an incorrect Ohm value to the fuel pump control unit, and the fuel pump control unit refuses to run the pump, except when transitioning through the correct resistance value as the power to the coil is either connected/disconnected at the various points I indicated.

 

Does this issue sound at all reasonably connected to an improper resistance value of an ignition control module?

 

Can anyone else verify what the resistance value of an ignition control module is/should be in a currently running '85 BRAT with a Hitachi carb and Hitachi distributor?

 

Is that $92 ignition control module actually the one I need to get?  I don't want to buy it only to find out its resistance is also out of tolerance and my BRAT still won't run.

[jono]

What an epic story of great detail you wrote there, cant criticise you for that !

 

Those modules are not only for these era Subes, but can work in many Japanese cars with Hitachi distributors so it would be interesting to see if their manuals indicate same values as Subaru in the Chilterns. Could be a misprint in any manual also !

I commend you on your ability to check and understand most of this stuff, and you sound quite capable of making a temporary diagnostic bypass of the fuel pump safety control module that is looking for a signal from the coil which would be measured in Ohms, but then beyond me is are they square or round waves? Shove a resitor wheel in between coil and safety pick up as I had to in order to dial in my tacho.

 

There are two things that can really trick you with these old beasts, dodgy fusible links and crud on the insides of the fuel line that tends to change in restriction size on colder temperatures, but I think you did clean out the insides of entire fuel lines and I know, you are chasing an Ohm problem in far greater detail than many of us understand.

 

This is where it is time for you to buy a going wreck to cure the disease you are catching to interswap bits.

Each time a module has let me down, it has given subtle warnings like a bit harder to start, then I need to ride my bike to fetch spares, but now I carry a spare module and two flat blade screwdrivers as a lucky charm. I have fitted $100AUD and US$40 and never had them fail me yet. Never measured their Ohms either, didnt know you could. Can you give us all a tute?

 

As an alternative diagnostic, earlier EA81 had a points dizzy. Maybe if you have torn enough hair out, daughter shed enough tears coz dad is not as good with cars as he thought ...maybe a points dizzy, coil to suit, and resistor thing in its ceramic housing and teach daughter about Ketterings system fails like crusty points, burnt out points, worn rubbing blocks, bad earths and failed condensors??

 

Oh, yeah, ignition switches can get a bit crappy too, some need to install relays for the starter mtor, but I am also thinking a relay for ignition power would not be a bad thing, using a relay with fuse in its pouch and use a fues that has a blown indicator built in.

Edited October 25, 2017 by jono

[mhisstc]

A misprint in the Chilton's manual regarding the ignition module was a consideration since I think the second value in the range of values for the primary side of the coil shown above is a misprint.  That's why I wanted to see if anyone can provide me with an Ohms value of their ignition module in a currently running vehicle.

 

The Chiltons manual shows testing of the ignition module (signal generator) by disconnecting the wires leading to the module and probing the leads with a multimeter.  I did this, and also tested it directly on the terminals of the module inside the distributor by unpluggin the wires at the module.  Again, on the "good" modules, having the leads hooked up one way showed infinity Ohms like and open circuit, while swapping the leads showed me between 820-830 Ohms.  The range specified by Chiltons is 130-190.  I didn't write it down, but I believe the first time I ran through this with the original module before it went bad, its values fell within the specified range.

 

I have an actual '84 Subaru factory manual that's basically the same for an '85, but the one thing it does not show is what the Ohm value of the signal generator (ignition module) should be.

 

I don't want to go back to a points based ignition system if I don't have to, but it's not out of the question.

 

The fuel system is completely cleared out and the fuseable links look good.  But it is clearly a no spark issue since if it was a no fuel issue it would run for a short time if I poured a little fuel in the carb.

 

It looks like my next step in diagnosis is to double check the fuseable links and try and bypass the fuel pump control unit.

 

I know the tumbler for the ignition key is worn as it is frequently difficult to turn the key on and off, but I removed the actual switch from the back of the ignition key tumbler housing and it seems to operate fine.  I could jumper that at the terminals to see if that is where the problem lies, but I don't think it is.  I have a theft recovery '91 Lexus LS400 I bought at an auction we converted to a series of switches instead of a key to operate since the ignition switch was jacked and we don't have a key, but I was trying to avoid that on this vehicle. 

[Gloyale]

So, you aren't using the key?  Just turning the switch with a screwdriver or something?  When you turn the little "t" shaped recess in the ignition switch, if you are pushing "in" too much it can interupt the contacts for the IG circuit while completing the starter circuit.  Put a test light on the coil + and watch that it stays lit while cranking.

 

Honestly.  I think you are chasing the wrong things.  The distys in these rarely ever fail.  and the chance of 3 of them being failed in one vehicle and still no change.  Nearly zero.  

 

There is something else going on.  It sat for along time.  Any sign of mouse damage?

[mhisstc]

I really think it's still a lack of spark caused by either a faulty ignition control module or a module with an incorrect Ohm value because it ran fine except for being a little "sputtery" when I first got it going after sitting for so long. Then it suddenly failed to start and had zero fuel pump sound when cycling the key. There was no resistance value read on the original ignition module and that's when I decided to replace the entire distributor the first time. After dizzy replacement, I immediately got the fuel pump to run briefly as I cycled the key and it fired right up and ran perfectly... ...until it failed to start again after several days along with no fuel pump sound as the key was cycled. Again, no resistance value could be read on the ignition module. That's when I replaced the dizzy a second time. After that replacement, I got no fuel pump sound as I cycled the key, and I refused to start. But this time the resistance value was outside of what was indicated as "good" in the Chilton's manual. Rather than warranty a second dizzy, I decided to replace just the ignition control module. Same result. No fuel pump sound. No start.

I was using a key, but the occasional flakiness of getting the worn key to turn in the worn tumbler led me to take the actual switch off the back of the tumbler and turn it with a screwdriver merely for the sake of ease turning it. I am being careful to not push the screwdriver in to interrupt the contact. I also did put a test light on each of the leads on the ignition switch, and they are all doing what they are supposed to be doing as I cycle it through LOCK, OFF, ACC, ON, and START. So I'm pretty confident it's not the ignition switch.

I also checked the three fuseable links under the gray cover in the engine bay and they are all good.

The next thing I did was jumper the Fuel Pump Control Unit so the fuel pump would come on at all times when the key was switched on. I had some concerns doing this. I referenced a couple other threads on this forum for guidance, but the wires referenced in those threads didn't quite match up with mine. The specific thread indicated one should jumper the 12V (B/W) wire to the pump (Blue/Black), but my wires weren't like that. So I discovered on my own what each one of them does and successfully jumpered the power lead to the pump. I definitely had the pump running when the Ignition switch was in the ON and START positions, and the throat of the carb was definitely wet with fuel when trying to start it, and I smelled fuel with the air cleaner housing lid off. Unfortunately, still no start.

But here is what I discovered when I while I was testing out the Fuel Pump Control Unit. I'm not sure what it all means, but it might help with some additional trouble shooting.
This is a representation of the connector and wire colors coming out of the connector on the FPCU.

​-----------------------------------------------------
|  med. thick    |  thick        | med. thick double|
|  double blue   |  black        | blue/red stripe  |

​-----------------------------------------------------
|  thin yellow   |  thin blue/   |  thin            |
|                | black stripe  |  black           |

​-----------------------------------------------------
                    |            |

​                    --------------

thin yellow wire = ON when ignition switch is ON and START. I don't know what this is.
medium thick double blue wires = always OFF. I don't know what this is.
thick black wire = ON when ignition switch is ON and START. This is the power wire from the Ignition switch.
medium thick double blue/red stripe wires = always OFF. These are the wires that run the fuel pump.

To run the fuel pump while the ignition switch is ON or START, I jumpered the thick black wire to the double medium thick blue/red stripe wires.

The interesting thing is, when pulling the coil fuse as I had done previously to get the fuel pump to run as if the ignition switch had been cycled from OFF to ON, both the medium thickness double blue/red stripe wires AND the medium thick double blue wires lit up and pulsed in unison with the fuel pump as it ran.

I also jumpered the plain blue wires along with the blue/red stripe wires with the power wire from the ignition switch. No luck.

I still cannot get this car to fire up and run under any of these other conditions.

So unless I there is something wring with the FPCU as I've tested it, I keep going back to the ignition control module as the culprit as it seems like it's really the only thing that's different in my run vs. no run conditions.

I'll go back and put a test light on the coil + to verify if the power is there during cranking.

And yes, there were mice in the interior. Those have been cleaned out and the only damage they seemed to do was to the radio antenna wire right next to where their nest was located.

Edited October 25, 2017 by mhisstc

[mhisstc]

I did put the test light to the coil + and verified it does have power there during cranking.

 

I could chalk up the first two ignition modules failing to potential over/under voltage issues due to the bad voltage regulator in the alternator as those units wouldn't even return a resistance value when I put the multimeter to them.

 

However, the one in the second new distributor and the one I got from OReiley's do return resistance values.  Those two just happened to be in the 820-830 Ohm range instead of the 130-190 Ohm range specified in the Chilton's manual.

 

If someone could find any kind of reference value in a factory Subaru manual or literature, or get a value from a Hitachi distributor ignition control module in a vehicle that is currently operational, that would be a huge help in either confirming or denying my suspicion that the module is the problem.  I think the next most likely culprit might be the Fuel Pressure Control Unit, but that seems to be functioning OK.  I haven't had a lot of time to check out the wiring diagram in the '84 Subaru manual I have, but a quick check of the Chilton's wiring diagrams show the 6 wires attached to the Fuel Pump Control Unit (Revolution Sensor) are:

* ground 

* fuel pump

* carb choke

* ACC

* IG (+)

* ignition coil (-)

 

So along with what I determined earlier:

ground = thin black wire

fuel pump = blue/red stripe wires

carb choke = blue wires

ACC = thin blue/black stripe wire

IG (+) = thick black wire

ignition coil (-) = thin yellow

Edited October 25, 2017 by mhisstc

[mhisstc]

I finally got the time to go through the factory Subaru manuals I have on hand for some additional guidance.  I have a '77, '81, and '84 manual, but not an '85 manual.  The '77 and '81 ignition systems are a little different than the '85, but they have great troubleshooting flow charts for the ignition system.  The '84 manual depicts an ignition system similar to the '85, but it doesn't have crap in the way of a trouble shooting flow chart like the earlier ones.

 

Going through the trouble shooting charts for the earlier models only got me so far until it referenced the grounding of the "ignition control unit side terminal at the three pole connector".  Well, the '85 BRAT doesn't have that.  Besides that, the flow charts were pretty complete.  I did manage to figure out the Chilton's manual value of 130-190 Ohms for the ignition control module is based on the Nippondenso distributors. The Hitachi distributors should have an ignition control module value of 600-850 Ohms, which the Chilton's manual doesn't indicate.  That means the module that came in my latest distributor, and the replacement one I bought for it, are probably both OK with their values of 820-830 Ohms.  I guess I have a spare now.

 

It looks like Gloyale was right on that one.

 

With the reference to grounding in the flow chart, I checked all of the ground wires in the engine bay and on the fuel pressure control unit to make sure those were all connected and didn't have a large resistance on them that would indicate a faulty connection.  They were all OK.  Now every single ignition component I know how to check has been checked and they all seem to be fine. I even verified I can manually make a spark with the coil from the high tension lead to engine block.

 

So that still leaves these questions to be answered.

* Why is there still no spark at the spark plugs?

* Why won't the fuel pump prime the carb when turning the ignition switch from OFF to ON?

* Why won't the fuel pump run when the ignition is in the START position?

* Why will the fuel pump prime the carb like it should if I disconnect the yellow wire that leads form the coil (-) to the fuel pump control unit (revolution sensor), or I pull the coil fuse when everything is hooked up and the ignition switch is turned ON?

* And why does this engine now refuse to run when it ran great previously?

 

Does this now all point to the Fuel Pump Control Unit (revolution sensor) as the little black box of evil that could be the possible source of these problems?

 

I like an automotive challenge, but I've always been able to figure them out.  This one has gone far to long with no resolution and it has me frustrated beyond belief.  I have no idea what to do next.

[jono]

Back to basics then...knock up a diagnostic temporary switch panel battery to coil, battery to fuel pump then battery to starter.....as if you were starting from scratch or trying to flog it! Do you know anyone you could fit your dizzy into their ea81 to try it?

[mhisstc]

Back to basics then...knock up a diagnostic temporary switch panel battery to coil, battery to fuel pump then battery to starter.....as if you were starting from scratch or trying to flog it! Do you know anyone you could fit your dizzy into their ea81 to try it?

 

Ugh!  That's what I was afraid of.

 

I wish I had a distributor and fuel pump control unit that are currently known to be operational that I could swap out with mine. I think I own the only ea81 powered vehicle within 200 miles.  We do occasionally make it out to the Colorado Front Range area, so I may try and post an add on Craigslist and see if I can find one of each.  I do have one other acquaintance in New Mexico that is a Subie mechanic.  I may contact him and see if he either has those parts on hand or could snag them for me if he runs across them.

[naru]

Fix one thing at a time.

You won`t get fuel w/o spark.

 

Put your test light on coil -.

If it lights up w/cranking but does not pulse,then the module or the wires to it are bad.

 

You cannot test a Hitachi module w/an ohmmeter.

Since it is a semiconducter device,ohmmeter readings are MEANINGLESS.

 

The diode check function of your multimeter is more useful especially if you have a good module to compare to.

 

Overvoltage can kill the modules.

So can bad or disconnected spark plug/coil wires.Test THEM w/an ohmmeter.

 

The FPCU is not meant to prime the carb.

The carb already has fuel in it.

Edited October 26, 2017 by naru

[Gloyale]

I did put the test light to the coil + and verified it does have power there during cranking.

 

I could chalk up the first two ignition modules failing to potential over/under voltage issues due to the bad voltage regulator in the alternator as those units wouldn't even return a resistance value when I put the multimeter to them.

 

However, the one in the second new distributor and the one I got from OReiley's do return resistance values.  Those two just happened to be in the 820-830 Ohm range instead of the 130-190 Ohm range specified in the Chilton's manual.

 

If someone could find any kind of reference value in a factory Subaru manual or literature, or get a value from a Hitachi distributor ignition control module in a vehicle that is currently operational, that would be a huge help in either confirming or denying my suspicion that the module is the problem.  I think the next most likely culprit might be the Fuel Pressure Control Unit, but that seems to be functioning OK.  I haven't had a lot of time to check out the wiring diagram in the '84 Subaru manual I have, but a quick check of the Chilton's wiring diagrams show the 6 wires attached to the Fuel Pump Control Unit (Revolution Sensor) are:

* ground 

* fuel pump

* carb choke

* ACC

* IG (+)

* ignition coil (-)

 

So along with what I determined earlier:

ground = thin black wire

fuel pump = blue/red stripe wires

carb choke = blue wires

ACC = thin blue/black stripe wire

IG (+) = thick black wire

ignition coil (-) = thin yellow

 

resistance for the hitachi distributor D4r80-03  is pick-up coil per 82 FSM (should be same part in your brat) says 720 ohms.  

 

2wd  Nippondenso distributors are listed at 160 ohms.  Sounds like Chiltons used that spec instead of the 4wd.  Chiltons sucks for these cars.  Frequent disinformation.  Do not trust Chiltons for specs like that.  Sometimes they are good for pictures but that's about all.

 

 

I would kindly suggest pulling and reinstalling hte disty to make 100% sure you've got it timed right.  double check the leads from the disty to coil.  Make sure the Black wire is on + and the yellow wires on -  

Edited October 26, 2017 by Gloyale

[mhisstc]

Fix one thing at a time.

You won`t get fuel w/o spark.

 

Put your test light on coil -.

If it lights up w/cranking but does not pulse,then the module or the wires to it are bad.

 

You cannot test a Hitachi module w/an ohmmeter.

Since it is a semiconducter device,ohmmeter readings are MEANINGLESS.

 

The diode check function of your multimeter is more useful especially if you have a good module to compare to.

 

Overvoltage can kill the modules.

So can bad or disconnected spark plug/coil wires.Test THEM w/an ohmmeter.

 

The FPCU is not meant to prime the carb.

The carb already has fuel in it.

 

The fuel system does appears to be fine with the lack of spark being the real issue.

 

Good to know about the Hitachi module. What is the proper way to check them?

The first two were most likely killed by the higher voltage before I replaced the alternator.

And according to my Ohm meter, the good units are showing an Ohm value between 820-830 while the bad ones show infinity.

 

Maybe "prime the carb" was a poor choice of words when referencing what is going on when the key is turned to the ON position. When everything is operating correctly, the fuel pump does run briefly to push fuel through the system prior to startup.

[mhisstc]

resistance for the hitachi distributor D4r80-03  is pick-up coil per 82 FSM (should be same part in your brat) says 720 ohms.  

 

2wd  Nippondenso distributors are listed at 160 ohms.  Sounds like Chiltons used that spec instead of the 4wd.  Chiltons sucks for these cars.  Frequent disinformation.  Do not trust Chiltons for specs like that.  Sometimes they are good for pictures but that's about all.

 

 

I would kindly suggest pulling and reinstalling hte disty to make 100% sure you've got it timed right.  double check the leads from the disty to coil.  Make sure the Black wire is on + and the yellow wires on -  

 

I'm new to the Subaru game as of this year, but yes, that's exactly what I've found out and should have known from previously using the Chilton's manuals with my Mustangs.  I regularly use a combination of 4 different manuals with them including the Chiltons, Haynes, the OEM factory manuals.

 

I pulled the distributor and double checked it was properly indexed, but then I also pulled it out again and re-indexed the distributor with the marks that place the rotor at the #1 cylinder terminal along with ensuring the cylinder #1 piston was at TDC on the compression stroke with the 0 deg mark on the flywheel in addition to checking the resistance of all the plug and distributor wires.  Still no spark being produced.

 

The basic ignition system really isn't that complicated, but being super paranoid about it all, I made sure I labeled all of the wires and verified the labels and connections against the wiring diagrams a minimum of three separate times.  Black wires to the positive (+) coil terminal and the yellow wires to the (-) coil terminal was something new I had to get used to and was why I had to triple check it to convince myself it was correct.

 

I still have the OEM distributor since I didn't have to turn it in as a core.  So I think my next step will be to clean up that distributor as best I can, install the replacement module I have into it, and see if anything changes.  It can't hurt, and there isn't any additional expense to do it at this point.

[naru]

 

The fuel system does appears to be fine with the lack of spark being the real issue.

 

Good to know about the Hitachi module. What is the proper way to check them?

The first two were most likely killed by the higher voltage before I replaced the alternator.

And according to my Ohm meter, the good units are showing an Ohm value between 820-830 while the bad ones show infinity.

 

Maybe "prime the carb" was a poor choice of words when referencing what is going on when the key is turned to the ON position. When everything is operating correctly, the fuel pump does run briefly to push fuel through the system prior to startup.

 

Best way to check them is w/them installed and a test light on coil - when cranking(you want pulses)

after verifying ground,power and signal wire connections at the module.

 

Or,use the diode check function of your multimeter to check voltage drops across the semiconducter junctions.

 

Bad modules usually show an open terminal.

Best to have a good module for comparison.

[mhisstc]

  

Best way to check them is w/them installed and a test light on coil - when cranking(you want pulses)

after verifying ground,power and signal wire connections at the module.

 

Or,use the diode check function of your multimeter to check voltage drops across the semiconducter junctions.

 

Bad modules usually show an open terminal.

Best to have a good module for comparison.

 

Test light on the (-) coil terminal = solid light when cranking, no pulses.

 

Doing the diode function test of the known bad module, it tests open in both directions.

Doing the diode function test on one of the modules that is supposed to be good, I get a reading of 913 in one direction, and open in the other direction.  The other supposedly good module was a similar value.

 

I also did a little searching online.  What I found indicates you can test diodes in either diode or Ohmmeter modes.

http://www.electronicshub.org/diode-testing/

 

In Ohmmeter mode, the known bad module tests as open in both directions, while the supposed good ones test as 820-830 Ohms in one direction, and open in the other direction.  That corresponds to the Ohms value shown in the Subaru factory service manuals for a Hitachi distributor module.

 

The instructions for my cheap little Leviton Multimeter say this about the diode mode:

"The display will then show the approx. forward voltage of this diode. If the test leads are connected the other way round, the display will show an overrange status of 1"

 

What it doesn't indicate is where the decimal place in that voltage should be.  I'm pretty sure it's not actually 913 or 91.3 Volts, but I don't kn

ow if I should assume a more realistic value of 9.13, or 0.913 Volts.

 

Any idea what a good module should read in diode mode?

Edited October 28, 2017 by mhisstc

[mhisstc]

I also went back and installed all of the original parts I had replaced (coil, cap, rotor, distributor) to go back and try and replicate a known running state.  The only thing different this time around, is that it had a new ignition control module installed in the old distributor since the original was definitely bad.

 

The results were the same as with all the new parts installed.

 

The vehicle will not start.  There is no spark.  The fuel pump will not briefly run when turning the ignition switch from OFF to ON.  I can still get the fuel pump to run continuously if it's jumpered at the FPCU to run when the key is ON.  And if I pull the coil fuse when the key is ON, it will run briefly if I pull the coil fuse.

[Knucklehead Saloon]

Have you tried a replacement fpcu ?

[mhisstc]

Have you tried a replacement fpcu ?

 

I have not.  I wish I could find one.

[jono]

ouch! I chucked one when I scrapped vehicle last year :oops:

 

just how many wires to each and which terminal of the coil please?

 

I think I found by stupid accident that a wire attached to the coil side to go to my tacho which would be same as connects to the safety doo dad above pedals, if that hits a ground, no spark, no start ...my antennae that had no radio, managed to dangle into my comparison tacho that was not powered up to power or ground but was still connected to the coil. By ripping the two components apart I suddenly had go spark again !!

 

I wonder if you test for the coil wire hook up side of coil to ground see if you get a reading.

 

Tach normally hoks up to neg side of coil yeah ? Wonder if simple test lamp connect to power and see if it earths through coils neg on the problem car. test a few other old same era coils with ign off??

[mhisstc]

There are three wires to each coil terminal.  The black to the positive, yellow to the negative.  All wires have been verified by tracing them back to the component they originate from and are labeled.

 

 

All components of the ignition system have been tested and found good along with all wires and grounds properly attached and in good shape.

The baseline timing has also been reset by indexing the #1 cylinder at TDC with 0 deg. on the flywheel.

All components of the fuel system have also been tested and found good along with all wires properly attached and in good shape.

The ignition switch has also been verified it is operating correctly.

 

And yet I still have no spark when cranking the engine and the fuel pump refuses to operate.

 

So what I am left with?

 

The only thin I can think of is the black box shown below.  The Fuel Pump Control Unit/revolution sensor.  This is the only component common to both the fuel system and ignition system that no one has been able to tell me how to properly test, and for which my searches have found no test procedures to verify correct operation.  So now I'm looking for one of these for an '85 BRAT with a manual transmission.

 

Are these things still available through the Subaru dealership network, or are they going to be a junk yard/parts car only kind of find?

 

Edited November 6, 2017 by mhisstc

[JRach]

I know your frustrations as i'm having the same issues currently with my 82' Brat. 

 

It sputtered and died on me while driving home about a year ago. I towed it home and parked it in the garage and haven't had a chance to look at it until now. 

 

Your symptoms sound identical to mine, so i'll keep you posted on what I find. If jumping the Fuel Pump Control Module results in the fuel pump running with the ignition on, I'd think that would eliminate it as the culprit. As I understood it, the fuel pump controller will prevent the pump from running without spark and not the other way around. 

[mhisstc]

 

 

 

Your symptoms sound identical to mine, so i'll keep you posted on what I find. If jumping the Fuel Pump Control Module results in the fuel pump running with the ignition on, I'd think that would eliminate it as the culprit. As I understood it, the fuel pump controller will prevent the pump from running without spark and not the other way around. 

 

 

I'm definitely interested in what you find out.

 

What I mean by jumpering the FPCU is that I'm essentially bypassing what's in the black box and I'm able to get the fuel pump to run continuously when power is applied. So, the pump works and I know I'm getting power to the black box.  I've still never been able to get it to start in that condition, which should mean that I'm still not getting any spark.  Everything I've read, also seems to indicate that if you have spark, the fuel pump will run.  But what I'm wondering is if there is some feedback circuit in the module that says everything is OK or not OK and then send a spark signal back to the ignition system. What exactly happens in the black box has never been clear and there is no schematic for that.

 

That said, a mere one hour ago, I picked up my brand new rev sensor at the Subaru dealership.

Pics to follow.

[mhisstc]

 

This evening I picked up a brand new FPCU for my '85 BRAT.  As you can tell, it doesn't look exactly the same, but the parts person who found it for me has over 17 years experience at the dealership.  The person I talk to when I picked up the part assured me if he was the one who found it for me, it's the right part.

 

Apparently, if what I was told is correct, this was also the ONLY brand new part in the entire U.S.A.  That's right.  There was only one of these in the whole country, and now I have it.

With tax, it was just shy of $190.  Ouch.  I sure hope it works.  If not, I will be totally stumped with this issue.

 

I didn't take a picture of it, but right outside the front door on display at the dealership was a very nice light metallic blue '85 BRAT.  The only wear I could see on it was where a shell had been on the bed. 

[jono]

I heard they were double that price here in 0z. You got the only one!

 

If you have time do you think it would help to test those six wires to see what they have?

 

When I junked my 84 I thought about saving that box but all I did was think

[mhisstc]

I heard they were double that price here in 0z. You got the only one!

 

If you have time do you think it would help to test those six wires to see what they have?

 

When I junked my 84 I thought about saving that box but all I did was think

In post #5 above, I did a little ASCI schematic of the plug with the colors and purposes listed.  It will be a couple more days before I get to plug that black box into the car and actually test it out with fingers crossed this was actually the issue.  At that time I'll try and get a couple more actual pictures and provide labels of everything now that I have more practice loading and linking pictures to my Gallery.