1984 EA81T - DOA Project

[naru]

Do you have a copy of the wiring diagram?That goes a long ways.

 

I`ve never been able to figure out what the Ti monitor is.

 

D-check jumper is the green test connectors for reading codes etc. under the dash.

 

Pressure switch monitors boost.Switches at 1psi IIRC.

 

Throttle switch is on the throttle body.

 

There is only one barometric sensor inside the ECU.

I know it looks otherwise.

 

Some ECU power sources are switched,some are not.

 

FICCD= Fast idle control device

It is a solenoid that opens a bypass passage to increase idle speed w/AC on.

I have no AC,but, I have a FICCD.

 

Line end code output only goes to the yellow 9 pin test connector under the dash.I suspect this is energized at the same time as the O2 light on the ECU.

 

My understanding is that 1984 California spec EA-81ts had dedicated ECUs.IMO,that pin is some kind of holdover from 83 when there was only 1 ECU.

 

Airflow meter pin 5 is the ground.

I`m thinking the resistor on pin 4 sets/stabilizes the supply voltage to the potentiometer.

[naru]

Found this in a patent application.

Seems to explain pin 4 rather well.

 

"The computor 11 is applied with signals corresponding to the voltages US and U FIX to compute the amount of intake air. The amount of the intake air Q can be obtained by the following formula: Q=A(U FIX -US)/UB "

 

Seems it allows the ECU to make an accurate airflow calculation despite variations in the regulated 5 volt supply.

 

Some MAF stuff.

http://the944.com/afm.htm

http://www.gomog.com/articles/EFIflap.html

http://www.clarks-garage.com/shop-manual/elect-22.htm

Edited March 20, 2011 by naru
maf stuff

[tahuyahick]

Do you have a copy of the wiring diagram?That goes a long ways.

 

I`ve never been able to figure out what the Ti monitor is.

 

D-check jumper is the green test connectors for reading codes etc. under the dash.

 

Pressure switch monitors boost.Switches at 1psi IIRC.

 

Throttle switch is on the throttle body.

 

There is only one barometric sensor inside the ECU.

I know it looks otherwise.

 

Some ECU power sources are switched,some are not.

 

FICCD= Fast idle control device

It is a solenoid that opens a bypass passage to increase idle speed w/AC on.

I have no AC,but, I have a FICCD.

 

Line end code output only goes to the yellow 9 pin test connector under the dash.I suspect this is energized at the same time as the O2 light on the ECU.

 

My understanding is that 1984 California spec EA-81ts had dedicated ECUs.IMO,that pin is some kind of holdover from 83 when there was only 1 ECU.

 

Airflow meter pin 5 is the ground.

I`m thinking the resistor on pin 4 sets/stabilizes the supply voltage to the potentiometer.

 

I've got one of those simplified diagrams that tend to really annoy me. But if I think of it as a stand-alone harness, then everything is shown. Just not in the locations. And a real miracle - my diagram has numbers on the EGI pins!

 

More notes to write-up here, thanks again. You really get the homework done! Awesome!

 

I should've tried this already, I can connect a testlight to pins 3 & 4 and then use my DMM to measure voltages.

 

This is showing what I measured on my AFM circuit board:

 

 

It sure doesn't look very complicated when you see it like this.

[tahuyahick]

Found this in a patent application.

Seems to explain pin 4 rather well.

 

"The computor 11 is applied with signals corresponding to the voltages US and U FIX to compute the amount of intake air. The amount of the intake air Q can be obtained by the following formula: Q=A(U FIX -US)/UB "

 

Seems it allows the ECU to make an accurate airflow calculation despite variations in the regulated 5 volt supply.

 

Some MAF stuff.

http://the944.com/afm.htm

http://www.gomog.com/articles/EFIflap.html

http://www.clarks-garage.com/shop-manual/elect-22.htm

 

Ok, I understand the intent. I'll have to ponder the ramifications of this circuit, it looks very useful for other applications. So if I understand that correctly, pin 4 is getting the regulated 5-volt supply positive. Pins 3 & 2 will show as a ratio of each other which will stay the same ( for a particular vane position) no matter what happens to the voltage level at pin 4.

 

I haven't checked the links yet. I'll do that when I re-arrange my note taking. Thanks! I've got a lot of testing to do before I try cranking the engine over again.

 

ps - did that formula give the definition on those variables? U-Fix, U-S & U-B are in volts, right? What's Q? CFM? And A? Is that a conversion factor?

Edited March 20, 2011 by tahuyahick
Last minute question

[tahuyahick]

http://the944.com/afm.htm

 

Doh! - "You can not use an ohmmeter to test an AFM's potentiometer. It will jump about meaninglessly. You must test it as it is being used. You have to force a voltage UV and measure the output voltage UP. This can be done with the AFM in the car and the ignition on."

 

Uh, you mean like what I've been seeing all this time?

[naru]

http://the944.com/afm.htm

 

Doh! - "You can not use an ohmmeter to test an AFM's potentiometer. It will jump about meaninglessly. You must test it as it is being used. You have to force a voltage UV and measure the output voltage UP. This can be done with the AFM in the car and the ignition on."

 

Uh, you mean like what I've been seeing all this time?

 

I thought that was an interesting statement as well.Not sure I agree.

 

After all,if the resistance "jumps around" so will the output voltage.

 

Ufix etc.are voltages.A is a constant.Q is air quantity in whatever units you like according to the constant.

 

In the links,people move either the wiper arm or circuit board so the wiper travels on an unworn portion of the track.

 

Never knew they trimmed the resistors with a laser!

 

I think the Ti monitor is strictly an output for the Subaru Select monitor diagnostic equipment.

 

Not all that relavent,but,here is the patent if you want to read it.

http://www.freepatentsonline.com/4546647.html

Edited March 20, 2011 by naru

[tahuyahick]

I thought that was an interesting statement as well.Not sure I agree.

 

After all,if the resistance "jumps around" so will the output voltage.

 

Ufix etc.are voltages.A is a constant.Q is air quantity in whatever units you like according to the constant.

 

In the links,people move either the wiper arm or circuit board so the wiper travels on an unworn portion of the track.

 

Never knew they trimmed the resistors with a laser!

 

I think the Ti monitor is strictly an output for the Subaru Select monitor diagnostic equipment.

 

Not all that relavent,but,here is the patent if you want to read it.

http://www.freepatentsonline.com/4546647.html

 

Well, I just connected an ATX power supply across pins 4 & 5. The loaded supply voltage is 11.33 Setting my DMM to a manual range selection and connected to pin 2, I see 0.94 at the wipers rest position, moving the vane slowly results in a very smooth increase in output voltage ending in 7.23 volts at the highest travel. There were no reverses in voltage rise, or any kind of troublesome spots in the output signal, so I'm gluing this shut with some dessicant and move on to testing the harness wiring for the AFM.

[tahuyahick]

Darn, it's on a curve! That might mean programming a $20 logic controller for a sensor interface. I'll just shelve that idea for a more desperate rainy day!

 

But after looking further into this, it's not actually a curve that's being outputted. If I go this route, I'd be using a hotwire sensor and it's a moving vane that creates the curve, but the resistor network is very carefully designed & laser-tuned to correct the value and output a linear signal. This era of computer is setup to expect a linear input to designate the volume of airflow, which is absolutely perfect! The newer computers had their software changed to use a cheaper AFM that outputs a log signal which the computer must then convert into the correct value. So, because the earlier AFM was designed to output an actual airflow value, it would be very easy to use a simple hotwire controller that calculates an airflow value and only make sure the voltage range is matched correctly. I'm supposed to sell this car, so I might not actually do this. But if anyone else would be interested in trying this out, I'd be very curious in what results!

Edited March 20, 2011 by tahuyahick
clarity

[naru]

Curiosity got the better of me.

I measured my MAF resistance.Us to ground(pin 2 to 5).I got 80-450 ohms.

Like you,I found the transition to be not all that smooth.

 

I`ve read of attempts to convert vane MAFs to hotwire style on the net.

None were sucessful.

 

IMO,your fuel pressure is too low.

Should be 36psi above manifold.

 

That combined w/lack of starting enrichment(code 12) would likely prevent starting.

[tahuyahick]

Curiosity got the better of me.

I measured my MAF resistance.Us to ground(pin 2 to 5).I got 80-450 ohms.

Like you,I found the transition to be not all that smooth.

 

I`ve read of attempts to convert vane MAFs to hotwire style on the net.

None were sucessful.

 

IMO,your fuel pressure is too low.

Should be 36psi above manifold.

 

That combined w/lack of starting enrichment(code 12) would likely prevent starting.

 

Uhm, fuel-pressure above manifold? Why did that give me a troubling feeling?:-\

 

I'm reading pressure from a standard 100 psi pressure gauge connected via a t-fitting inserted between the fuel filter and the engine. The book says 30 to 36 with the vacuum line disconnected & plugged, holding at 30 when the pump is off. The book also specifies that the regulator should be holding 30 psi after the engine is turned off for five minutes.

 

According to the book I have, it should not be 36 above the manifold pressure level while running. But it will be that way when the engine is off!

 

A lack of starting enrichment...darn pesky computer! Why can't it just understand what I'm thinking?

[naru]

Manifold pressure is lower than atmospheric when idling.

The difference between the 2 pressures needs to be 36psi.

 

Gauge pressure will be lower than 36 at idle.

36 w/engine stopped .

[tahuyahick]

Manifold pressure is lower than atmospheric when idling.

The difference between the 2 pressures needs to be 36psi.

 

Gauge pressure will be lower than 36 at idle.

36 w/engine stopped .

 

Well if I have to shim the regulator again, it's not really that big a deal. At least it isn't 60 plus!

 

Hey! I just thought of something, if the starting enrichment wasn't kicking-in but the pressure was at 60, then it would be enriched anyways, but would stay that way after cranking. Might be why it started to begin with. It's too bad I didn't look at the codes from the beginning. But I bet the code 12 was an issue before I got the car.

 

Well, I haven't done a thing yet to the car. It was nice enough outside I had to take my dirtbike out in the woods. But the next two days are my weekend, so maybe I'll get something done around the house...

[naru]

Well if I have to shim the regulator again, it's not really that big a deal. At least it isn't 60 plus!

 

Hey! I just thought of something, if the starting enrichment wasn't kicking-in but the pressure was at 60, then it would be enriched anyways, but would stay that way after cranking. Might be why it started to begin with.

 

That is what I was thinking too.

[carfreak85]

Stick with it. These cars are a lot of fun and once they are running right, they tend to stay that way.

 

Also, keep me in mind if the project gets old and you want to get out, I'd love to have an EA81T coupe again.

[tahuyahick]

Well, after a nice tall glass of home-made triple shot coffee & cocoa-mix...

 

I decided to ignore the lack of sensor-safe sealer and electrical-taped the AFM cover back into place and just threw that back into the car. Ignored the lack of a clip to hold the harness connector to the AFM, more tape please!

 

Funny, when I try turning the key on, I see a code 11, 12 & 14 on the first cycle, then it's just codes 11 & 12. Maybe I did something right inside of that AFM! I wasn't really sure about that part:grin:!

 

And I decided to unplug a mysterious green connector next to the computer. Hey! With the key on but not started, the pump stays off. So I arrange the fuel pressure gauge where I can see it and try cranking the engine to see if the pump kicks on, oh and the cars starts! Woo-Hoo! And the pump does indeed kick on and stay running.

 

And the engine is running kinda normal! So I drop some tools, run around up front and try bumping the gas by pushing on the throttle body end and the throttle immediately sticks wide open and whadda ya' know, it revs up all crazy-like, and it starts cutting of momentarily like there's some kind of rev limiter and something under the dash starts beeping. So I shut it off. With a quickness!

 

Yeah, the throttle cable got mis-routed at the throttle body. A restart using the gas pedal this time, and it's almost normal. So I check the fuel pressure and it's back to 60 plus. Darn!

 

Ok, one problem is I keep forgetting the vacuum hose to the regulator. That's one point for the leaks, home team still struggling.

 

Pressure is holding at 60 with the engine off, so I remove the return line to check if it's a blockage on that. But nope, just a slow drip coming from the regulator. So I must've not quite fixed that thing, or maybe there's some debris in the lines that's sticking the regulator closed. Yeah, right. Debris sticking valve issues usually mean the valve is unable to close and the pressure would be too low. I probably need to re-think the regulator fix. Maybe an aftermarket unit is in the works. But I can drive the car as it is now. That's progress.!!!