crank angle sensor???

[belizeanbus]

A question about the functioning of the crank angle sensor… I got this from a previous thread:

 

 

“The disty is the crank angle sensor which tells the ECU that the engine is turning, which cyl is firing and what RPM. So we know the ECU is getting in put from the crank angle sensor because it is out putting to the coil.”

 

 

My issue is a rebuilt engine I just installed and cannot get to start. Actually, I installed it about a month ago and then got tied up with some home repairs and the holidays and now I’m ready to take another stab at it. It has been suggested that the crank angle sensor may have gone bad/gotten corroded during the downtime of the engine rebuild, so my questions involve how to troubleshoot this thing…

 

 

• If the crank angle sensor is not communicating with the ECU, will it throw a code? Or will it throw a code only if you can get the engine to run?
  
• Will the fuel pump work if the crank angle sensor is not functioning?
  
• Will you have spark if the crank angle sensor is not functioning? If I understand the previous thread right, no CAS = no coil = no spark???
  

 

FYI, it’s a 1992 EA82 SPFI non-turbo. If I recall where I left off, I had spark and could get it to run for a few seconds with fuel poured into the injector. I’m getting no codes telling me anything is wrong… It turns over fine, belts are not broken… that’s the background. Now how do I rule the disty out as the problem?

 

 

thanks

 

 

[idosubaru]

 

 

 

• If the crank angle sensor is not communicating with the ECU, will it throw a code? Or will it throw a code only if you can get the engine to run?
  
• Will the fuel pump work if the crank angle sensor is not functioning?Will you have spark if the crank angle sensor is not functioning? If I understand the previous thread right, no CAS = no coil = no spark???

i think i replied to your previous post. you need to swap in a known good ditributor or replace the sensor (i've never heard of anyone doing it, but you can if you find a source for the sensor). i have had two distributors fail after a motor tear down. mine tested fine, had no CEL, had FUEL, had SPARK and the pinouts tested fine, i unplugged and replugged the connector....nothing still. swapped it out and both times the car started after much testing of other things. i don't know why, i can't explain, yes it's annoying, yes i wish there was a specific way to test it. BUT - spark and fuel are NOT efficient in ruling it out, i know that for sure. maybe they should be, but they are not. find a way to accurately test the distributor, focusing on fuel and spark are not ways to "rule it out".

 

 

good luck and let us know what you find.

[Cougar]

The CAS is INSIDE the disty, underneth the rotor. If it fails, the ECU has no way to determine the ignition timing. There will be no spark if the CAS doesn't work and a code will be generated. There is also a device called the ignitor (a transistor) in the ignition circuit that acts like the points used to. This can be a problem also but again there will be no spark if it is bad. I don't think a code will be generated if that goes bad or is intermittent since it is not checked by a input to the ECU.

[idosubaru]

The CAS is INSIDE the disty, underneth the rotor. If it fails, the ECU has no way to determine the ignition timing. There will be no spark if the CAS doesn't work and a code will be generated. There is also a device called the ignitor (a transistor) in the ignition circuit that acts like the points used to. This can be a problem also but again there will be no spark if it is bad. I don't think a code will be generated if that goes bad or is intermittent since it is not checked by a input to the ECU.

 

i agree these things *should* happen this way. but, i've had two failed distributors (still have them) that produced no CEL and i got spark and fuel. i've heard others say it's not supposed to happen like that and agree it shouldn't (would have saved me ALOT of time diagnosing) and i don't know what the exact problem is, but swapping the dist made the engine start, that's what i know (and i previously had fuel, spark). the second time i kept telling myself no way it was the distributor and i tested everything....then when i finally sucked it up and swapped, it started.

 

i'll need to do swap them again since i have 4 dist and don't know which two are bad. 'im curious to see if they'll do it again and i can test for differences.

[Cougar]

Do those distys have the ignitor mounted on them? If so, I would suspect that as the problem or the connection to it.

[idosubaru]

Do those distys have the ignitor mounted on them? If so, I would suspect that as the problem or the connection to it.

if you're asking about the XT6 then no the ignitor is where it is on the EA82's, not on the disty.

[85Sub4WD]

the ignitor is right below the ignition coil, generally they don't fail, but it is certainly possible

 

for the "official" troubleshooting/specs info go here, look under the EA82 section that has the fuel injection information - pretty much all SPFI systems are identical (save the 1986 MY - connector pinouts different, rest same)

http://ww2.finleyweb.net:9394/default.asp?id=142

it gives the specific nature of the CAS operation, and diagnosing a good/bad CAS

 

grossgary - are you sure your problem was not a bad cap/rotor, or even a bad ECU? I know some early 1986 SPFI ECUs tend to be a bit finicky I actually converted my car to SPFI before the manual was written - one thing that I do not think is in it is the fact that the grounding of the ECU case and the engine are CRITICAL to proper operation, in fact completely removing the ECU's case ground can destroy it (warning in FSM) I actually burned up two good ECU's this way before I figured it out

 

worse still, they seem to give a faulty CAS indication when they go, so I had three CASes trying to figure out what my problem was!

 

another possibility is a weak ignition coil/wires

 

anyway, the link should get you all the info you need - an analog multimeter with a traditional needle is great for checking the actual pulses, as the digital type don't allow you to see the actual rapid changes

[Cougar]

Since the bad distys don't generate a code or let the car start then I have to think that the timing pulses are getting to the ECU but are distorted somehow. Perhaps low voltage level. It would be interesting to see what a scope shows up on the waveform.

[rol1]

Sounds like what my 92 Loyale did when I bought it from the auction. It would pop for a second then die with a shot of gas. It was the fuel pump.

 

If it caught before, tried to fire, then the problem must be intermitent if its the dist or cas.

[85Sub4WD]

Since the bad distys don't generate a code or let the car start then I have to think that the timing pulses are getting to the ECU but are distorted somehow. Perhaps low voltage level. It would be interesting to see what a scope shows up on the waveform.

Hmmm ... If only I had an Electrical Engineering Lab class this semester .... the oscilloscopes we have can even capture images of the waveform digitally for computer useage

[idosubaru]

grossgary - are you sure your problem was not a bad cap/rotor, or even a bad ECU?

positive, i only swapped distributors and kept the (brand new) cap and rotor. same on the previous instance a couple years ago, finally swapped disty after many days/hours replacing everything and swapping MAF, Knock sensor, ECU..blah blah blah to no avail. replace disty and it ran fine. on this last time, i had pulled/reinstalled the wires multiple times and connected/disconnected the electrical testers. no codes, i tested every pin out at the ECU and followed the entire, convoluted, detailed "No Start" testing in the FSM...pages and pages worth and everything tested fine. i've owned about 12-15 XT6's, parted a few out and know them fairly well.

 

from now on i say replace it (but that's easy for me to say i have plenty of parts lying around).

 

this just occurred to me, i dare even say this as some people likely don't believe me up to this point, but let me mention an even stranger detail. i'm wondering if there is anyway for the CAS to become disoriented or misaligned internally? the first time i could actually get the car to run (not very well though, but driveable) by lining it one or two teeth OFF intentionally. line up the disty correctly and it wouldn't even start if i turned the timing all the way as far as it could go. lined it up OFF intentionally a couple times (more or less by accident) and it ran.....i agree, totally weird and believe i would have used every cuss word in the book at the time i was so frustrated. that's why i say check it if you can't find anything else now that i've had it happen twice. and both times it never happened while driving the car or using it...but after the car had sat awhile....it wouldn't start up after running fine before. huck, john and others from xt6.net helped me through that first nightmare, they probably recall and the details are posted all over xt6.net or the old yahoo groups.

 

i say swap disty if you can, it's easy enough to do and worth the trouble it may save.

[85Sub4WD]

this just occurred to me, i dare even say this as some people likely don't believe me up to this point, but let me mention an even stranger detail. i'm wondering if there is anyway for the CAS to become disoriented or misaligned internally?

That's not crazy at all - that is actually a very real possibility, in fact I saw (somewhere) a rather expensive gadget to "align" the plate/light

 

Realize that below the metal cover on a CAS, there are two lights, sensors, and sets of perforations, the outer has (as I recall) 360, the inner four (for ignition).

 

If one of the sensors becomes damaged, the computer knows because it recieves one set of signals - it has two different error codes, one for each set of signals - if it gets no signal, usually it will give a weird error code, I can't remember which one it was, but something like starter switch failure, however I would not be surprized if earlier ECUs don't detect the problem properly

 

realizing these are all logic circuits, all the computer cares about is the 0-5v pulse, and there is a fairly wide operational range

 

the FSM on the link I posted details this specifics on the CAS operation, and it elaborates a lot more than I do on the operation

[idosubaru]

That's not crazy at all - that is actually a very real possibility, in fact I saw (somewhere) a rather expensive gadget to "align" the plate/light

 

so why would this misalignment occur while the engine was not run for a couple months and never while driving? i always assumed corrosion of some sort since it was always while "sitting". cars both ran perfectly fine before tear down (minus head gasket seaping).

 

belizianbus, do you have a means to swap distributors to check?

haven't heard back from you yet.

[85Sub4WD]

so why would this misalignment occur while the engine was not run for a couple months and never while driving? i always assumed corrosion of some sort since it was always while "sitting". cars both ran perfectly fine before tear down (minus head gasket seaping).

 

corrosion is also a possibility - anything that can interfere with the light being transmitted through the perforated disc and recieved by the photosensor can/will cause the CAS to fail to deliver the pulses - that means dust, dirt, corrosion, misalignment, oil, excessive shock, etc...

 

that said, I have not seen as many CASes fail as you might expect given the technology employed (I have never had a bad one actually) - why? - I'm guessing the seals are good enough, but I don't know for sure

 

make sure the timing and all (plugs, wires) are right too - that can also cause crazy issues

 

good luck

[belizeanbus]

Wow... thanks everyone for the good discussion...

 

I have a few things to check once the weekend comes around before going for a new disty. I want to make sure that the fuel pump is functioning properly, double check timing and all electrical connections.

 

Then I'll start looking for a replacement distributor. Bummer is, I have one in another Soob, but it's parked at my folk's place, a few hundred miles away. I'll likely post on the marketplace in case anyone has a functional extra or is parting out a car...

 

Thanks again for the good discussion... I'll be getting back to it once the wekend rolls around.

 

belizeanbus

[oldude]

I seem to have the same problem, but on an EA81. I get 2 codes. 11 and 22. Mostly 22

 

I have gone through 4 distys. Changed distys from original with ignitor and pick-up coil, to one from Brat, same EA81, but different insides. All ran OK but not for long.

Changed coil

Changed wires

Changed ECU

What could cause this to happen>>

Answer could help this person's question and from what I've seen, many others, too.

[belizeanbus]

Well, I'm bringing this one back to the top of the list, if for no other reason than to say that it does not appear to be the disty.

 

I found a supposedly good used one at a JY, and installed it. Same problem as before.

 

I don't have much time to spend on the car these days, so any leads the experts out there can give would be awesome.

 

To recap, I rebuilt the EA82 down to the headgaskets, put a new clutch and reinstalled, and since then it has not moved. I've rechecked all my electrical connections and they seem in place. I checked for spark. I have spark. It looks to me that there is a problem getting fuel into the system. I was hoping that if the crank angle sensor was bad, it would be what was interrupting the signal to the fuel pump and not allowing for fuel to flow.

 

I think it's a fuel problem because when I pour gas in the injector I can get it to run for, oh, about 3 seconds.

 

Now... If anyone has any magical tests/cures, I'm certainly not in love with this fuel system theory, so by all means, share your wisdom. If not, what would you do if your were hunting for the culprit int he fuel system? Check the electrical harness first? Should be 12V with ignition on or with engine turning over? Intermittent, or steady?

 

My logic is troubling me... although I think the fuel system in the culprit, I don't really see how removing the engine would trigger a perfectly functioning system to go down.

 

At any rate, the car's been sitting for almost 6 mos. now and I'm about to throw in the towel on this one. If anyone is in the area and can lend a hand, I'll certainly buy the beer.

 

Thanks,

belizeanbus

[idosubaru]

engine wiring harnesses fully seated? i know someone who had an issue they couldn't track down and eventually figured out that they had bent a pin on one of the connectors while inserting it. straightened the pin out and the mystery was solved. this was at the ECU though.

 

after 6 months is the gas no good? gas goes bad. i got an XT6 with that issue before. had been sitting awhile and wouldn't start until i got new gas in it.

 

is the injector good? it clicks/opens closes with 12 volts? or is this a constant duty cycle injector?

[Mark Humble]

You didn't by chance get the fuel lines going to the injector reversed? One is pressure and the other is return. If thats not it then the fuel pressure should be checked and the injector checked to see if it is working. For the injector test, if I remember correctly, the injector should have power to it with ignition on, and the ECU grounds one wire to activate the injector. And yes, fuel goes bad fast. I have been hearing that in Cali, it has a shelf life of 30 days. After that it goes down hill fast. I had one engine, an 11 hp Honda, with fuel that was 2 1/2 months old that would not start. This engine normally would start if you just looked at it. Put fresh fuel in and it started first pull.