Fried ECU

[davepak]

41 minutes ago, idosubaru said:

I think the wiring needs tested.  Honestly I've been humoring the other suggestions to a degree and just keep repeating the wiring issue thinking it's obvious there's a short and eventually you're going to have to test it - except maybe swapping in another injector - but it seems like we need to know for sure the wiring is good.  And if you're having problems this bad, all the time, it shouldn't be intermittent and should test bad somewhere. 

I would test all the pins from ECU plug to injector plug.  Disconnect them and test. 

I have heard of old XT's having running issues due to the wiring where it runs under the passengers side seat being damaged.  I haven't seen it myself so I'm not sure where exactly or what causes it, but I've heard of it a couple of times over the decades on XT's. 

 

 

 

Yes. That's the next call of action. I'm currently trying to make 1 ECU out 2 fried ones :/

I'll remove carpets and check both under the passenger and drivers side. Wiring has to be the issue. That and maybe another ECU if I can't salvage this one 

[idosubaru]

39 minutes ago, davepak said:

Yes. That's the next call of action. I'm currently trying to make 1 ECU out 2 fried ones :/

I'll remove carpets and check both under the passenger and drivers side. Wiring has to be the issue. That and maybe another ECU if I can't salvage this one 

You can just test the wiring and save yourself the work of pulling seats and carpeting. I'm just mentioning that I've heard of this happening in XT's before and you're having issues, maybe bewteen the ECU and injector - so it's worth testing.  Continuity and resistance, I think you only need to check the two injector wires from the engine bay to the trunk. 

Pull ECU plugs and injector plugs. 

If you don't have long leads (who does?!) - I have just run speaker wire or whatever long wires I have available from the engine bay to the trunk.  I've even used jumper cables before just as extensions - connect a short piece of wire to two (of the same color) jumper cable clamps, and use that as make shift "probes" to extend your multimeter reach. 

Remember to pull all your associated connectors when testing. 

There's nothing under the drivers side seat unless you have an XT6, the XT's have nothing - the ECU wires run under the passengers side. 

[davepak]

33 minutes ago, idosubaru said:

You can just test the wiring and save yourself the work of pulling seats and carpeting. I'm just mentioning that I've heard of this happening in XT's before and you're having issues, maybe bewteen the ECU and injector - so it's worth testing.  Continuity and resistance, I think you only need to check the two injector wires from the engine bay to the trunk. 

Pull ECU plugs and injector plugs. 

If you don't have long leads (who does?!) - I have just run speaker wire or whatever long wires I have available from the engine bay to the trunk.  I've even used jumper cables before just as extensions - connect a short piece of wire to two (of the same color) jumper cable clamps, and use that as make shift "probes" to extend your multimeter reach. 

Remember to pull all your associated connectors when testing. 

There's nothing under the drivers side seat unless you have an XT6, the XT's have nothing - the ECU wires run under the passengers side. 

Well, I'm pronouncing dead the new ECU, despite soldering attempts.

Im on the passenger's side checking the wires. Can't seem to notice anything bad, torn or cut. Just some dampness and a badly corroded ground point. I'll clean that now and I will do as @idosubarumentions@idosubarumentions: To test continuity with very long probe cables. Ah, and trying to get a pulled ECU from a junkyard nearby.. 

[naru2]

5 hours ago, davepak said:

I opened the newly acquired ECU and found a burnt piece. It's labeled D1320. 

 

 

Trace which output pin that transistor feeds.That will tell you which circuit drew too much current.

That does not look like an injector driver to me(could be wrong).I would expect the injector drivers to be on a heat sink.Perhaps the problem is elsewhere.

Should be no problem running 2 injectors in parallel as that is what the ECU does.3 is a different story.

[DaveT]

It is entirely possible for a wire to be broken - inside it's insulation,  inside the harness.   I had one once.  It was a pita to find.  Got it narrowed down with an ohm meter, moving the harness  it would open  / close.   Had to unwrap and remove the harness.   Finally saw an little bump in the wire - sure enough, it was broken right there, inside the insulation.  All of the strands, at that spot snapped.  The 2 ends bumping against each other.sometimes a connection,  sometimes not.

[davepak]

6 hours ago, naru2 said:

 

Trace which output pin that transistor feeds.That will tell you which circuit drew too much current.

That does not look like an injector driver to me(could be wrong).I would expect the injector drivers to be on a heat sink.Perhaps the problem is elsewhere.

Should be no problem running 2 injectors in parallel as that is what the ECU does.3 is a different story.

Actually, the first ECU fried on the heat sink, this new one fried right there at the base of the connector. And it happened when I attached a wire to split injector #3 into two to feed both injectors #3 and #4. On this test the car actually ran on 4 cylinders, but soon enough burning smell came and the ECU is toasted

I'm considering fabricating the darn wires all the way to the ECU 

 

 

Edited December 18, 2020 by davepak
wrong image

[naru2]

If your car was 87 1/2 or newer,I would say the resistor for injector #4 is shorted,but earlier models did not use a resistor pack.

Do you have a flapper MAF  and distributor equipped w/vacuum advance or hot wire MAF w/optical distributor?

[davepak]

2 hours ago, naru2 said:

 

Trace which output pin that transistor feeds.That will tell you which circuit drew too much current.

That does not look like an injector driver to me(could be wrong).I would expect the injector drivers to be on a heat sink.Perhaps the problem is elsewhere.

Should be no problem running 2 injectors in parallel as that is what the ECU does.3 is a different story.

Actually, the first ECU fried on the heat sink, this new one fried right there at the base of the connector. And it happened when I attached a wire to split injector #3 into two to feed both injectors #3 and #4. On this test the car actually ran on 4 cylinders, but soon enough burning smell came and the ECU is toasted

I'm considering fabricating the darn wires all the way to the ECU 

[davepak]

33 minutes ago, naru2 said:

If your car was 87 1/2 or newer,I would say the resistor for injector #4 is shorted,but earlier models did not use a resistor pack.

Do you have a flapper MAF  and distributor equipped w/vacuum advance or hot wire MAF w/optical distributor?

We have just had an Eureka moment. 2 fried ECUs and countless hours after:

We managed to pinpoint the wires for injectors 1,2,3 and 4 that come out of the ECU. In doing that we tested using a long wire for continuity as @naru2 suggested on all wires. We found all wires were continuous from ECU to each injector. HOWEVER, what we also found was that wires #3 and #4 are touching each other, there is a resistance of 0.26 Ohms between them! We tested this at the beginning right out of the ECU and the main engine harness therefore identifying the issue in between these points. This suggests the following :

The ECU controls 2 injectors at a time with one driver, 1 and 2 are fine and working. 

Injectors 3 and 4 are working and their harnesses are fine BUT only by disconnecting injector #4 the ECU is prevented from shorting between injectors 3 and 4. 

Originally the stock ECU was fried exactly on the driver /transistor/diode where injectors 3 and 4 operate. 

Wires 3 and 4 are touching each other at one point. The car would either start with 3 cylinders or not start at all with all 4 as of now. 

The next action is: Source a new ECU or try to fix one of them. 

Either identify the torn/broken wires and fix them or fabricate a separate wiring that takes ECU signals from ECU to injectors 3 and 4 and bypass the now known troublesome wires.

By confirming continuity among 3 and 4 wires we can confirm that this nullifies operation for these cylinders. 

I had uploaded a picture showing a wire labeled as ECU injector #3 but this was wrong, that wire was for something else, hence me frying the ECU. "You also learn by breaking things" 

The image below shows our Eureka moment, there should not be any reading between these prongs. We found a reading both at the beginning of the ECU and at the ending of the engine wire loom. Here are our culprits. 

I will work on this over the weekend and onwards with more updates. Thanks to @idosubaru @john in KY @el_freddo @naru2 @DaveT and all of you guys for the constant help. I think I'm nearly there 

[davepak]

3 hours ago, naru2 said:

If your car was 87 1/2 or newer,I would say the resistor for injector #4 is shorted,but earlier models did not use a resistor pack.

Do you have a flapper MAF  and distributor equipped w/vacuum advance or hot wire MAF w/optical distributor?

It's a flapper MAF and distributor with vacuum. 86 XT. As of now we've found wires for injectors #3 and #4 to be "touching each other" and this must be the reason why there is a short in the wiring affecting the ECU and forbidding the car to start on 4 cylinders. 

[idosubaru]

Good job, I'm glad you did those tests!  That's gotta feel good to know what's going on.  The next step you can do to save yourself some work: 

Disconnect the engine harness connector on the rear passengers side of the engine bay and try to determine if the wiring issue is on the intake manifold wiring harness, or the body side wiring harness. It'll be really easy now that you're all set up to do it. 

Repeat the same test you just did twice: 
1.  between the injector and the *engine side* of that large main connector 

and also

2.  between the ECU and the *body side* of that large main connector

That will tell you if the issue is bewteen the ECU connectors and engine bay or engine bay and injector.   Then you can address your repair to just the problematic section rather than rewire the whole thing. 

You could also choose points in between to narrow down.  The benefit to doing this is that if there's a pinch area or the harness was damaged due to some engine removal many years ago you can find other potentially broken or problematic wires as well. 

I've pulled conduit apart when tracing stuff like this and found the broke wire along with 2 others that would have been problematic in the future.  It's more common around doors and trunks, areas where the wiring is moving back and forth. 

[davepak]

1 hour ago, idosubaru said:

Good job, I'm glad you did those tests!  That's gotta feel good to know what's going on.  The next step you can do to save yourself some work: 

Disconnect the engine harness connector on the rear passengers side of the engine bay and try to determine if the wiring issue is on the intake manifold wiring harness, or the body side wiring harness. It'll be really easy now that you're all set up to do it. 

Repeat the same test you just did twice: 
1.  between the injector and the *engine side* of that large main connector 

and also

2.  between the ECU and the *body side* of that large main connector

That will tell you if the issue is bewteen the ECU connectors and engine bay or engine bay and injector.   Then you can address your repair to just the problematic section rather than rewire the whole thing. 

You could also choose points in between to narrow down.  The benefit to doing this is that if there's a pinch area or the harness was damaged due to some engine removal many years ago you can find other potentially broken or problematic wires as well. 

I've pulled conduit apart when tracing stuff like this and found the broke wire along with 2 others that would have been problematic in the future.  It's more common around doors and trunks, areas where the wiring is moving back and forth. 

Oh thanks @idosubaru! Yes it's a great feeling indeed. I tried to fix the ECU but it's beyond my repair capabilities. I will source another one hopefully today. 

We've narrowed down the problem from the ECU to the engine bay. I suspect somewhere under the carpet. Or maybe under the rear passenger seat. This Weekend I'll work on that. I would most likely place 2 brand new wires all the way from ECU to engine bay bypassing the now known issue. And attaching them to injectors #3 and #4. In my experience as well, I've seen attempts of fixing the original arrangement - wiring in this case- only for a new issue to develop. 

It is not preferred but it will have to do. As I'm not looking to dismantle the whole wiring loom for this darn wires. It might be a future project though 

I'll post updates over the weekend. Thanks as always! 

[idosubaru]

2 minutes ago, davepak said:

Oh thanks @idosubaru! Yes it's a great feeling indeed. I tried to fix the ECU but it's beyond my repair capabilities. I will source another one hopefully today. 

We've narrowed down the problem from the ECU to the engine bay. I suspect somewhere under the carpet. Or maybe under the rear passenger seat. This Weekend I'll work on that. I would most likely place 2 brand new wires all the way from ECU to engine bay bypassing the now known issue. And attaching them to injectors #3 and #4. In my experience as well, I've seen attempts of fixing the original arrangement - wiring in this case- only for a new issue to develop. 

It is not preferred but it will have to do. As I'm not looking to dismantle the whole wiring loom for this darn wires. It might be a future project though 

I'll post updates over the weekend. Thanks as always! 

Yeah that makes sense to just replace the wires.  Just hope that whatever damaged those wires doesn't damage other ones...I'd guess statistics are on your side for that since none of the harness goes through an area that sees motion like the trunk or doors do. 

Did you do your tests from the ECU connector to the injector or from the ECU to some other plug? 

If you tested to the injector - I'm saying there's a really easy main harness connector you could test and see if it's on the engine harness or in the body.  If it's on the engine that would be a much simpler wire run to repair and you wouldn't have to do the entire vehicle.  Just run it from the injector to the main wiring harness plug on the rear passengers side of the engine bay sitting above the transmission.  

[davepak]

53 minutes ago, idosubaru said:

Yeah that makes sense to just replace the wires.  Just hope that whatever damaged those wires doesn't damage other ones...I'd guess statistics are on your side for that since none of the harness goes through an area that sees motion like the trunk or doors do. 

Did you do your tests from the ECU connector to the injector or from the ECU to some other plug? 

If you tested to the injector - I'm saying there's a really easy main harness connector you could test and see if it's on the engine harness or in the body.  If it's on the engine that would be a much simpler wire run to repair and you wouldn't have to do the entire vehicle.  Just run it from the injector to the main wiring harness plug on the rear passengers side of the engine bay sitting above the transmission.  

We've tested both. From ECU to engine harness and from there to the injectors. The fault was found from ECU to engine harness. Meaning the cut /torn wires are in between these 2 points.  I just measured and checked so I can buy a proper length of wire to fabricate this bypass. I'll use insulated "T-Taps" to do this job.  Attaching the new wires as a bypass they'll be labeled and protected against rubbing and vibrations.. I'm learning enough with this issue!

I'll cut the offending wires, effectively isolating them. They'll be there, but they'll be dead. 

[idosubaru]

5 minutes ago, davepak said:

We've tested both. From ECU to engine harness and from there to the injectors. The fault was found from ECU to engine harness. Meaning the cut /torn wires are in between these 2 points.  I just measured and checked so I can buy a proper length of wire to fabricate this bypass. I'll use insulated "T-Taps" to do this job.  Attaching the new wires as a bypass they'll be labeled and protected against rubbing and vibrations.. I'm learning enough with this issue!

I'll cut the offending wires, effectively isolating them. They'll be there, but they'll be dead. 

Awesome.  I thought you only tested from the trunk to the injector.  Great. You must be excited to slap those wires in there and crank it up with a new ECU!

[davepak]

8 minutes ago, idosubaru said:

Awesome.  I thought you only tested from the trunk to the injector.  Great. You must be excited to slap those wires in there and crank it up with a new ECU!

Hahaha can't tell how excited, but I've got a bunch of other  stuff for the day. Including getting new wires and the actual ECU. I want to do this job good from start to finish! 

Thanks as always. More updates coming 

[idosubaru]

3 hours ago, davepak said:

Hahaha can't tell how excited, but I've got a bunch of other  stuff for the day. Including getting new wires and the actual ECU. I want to do this job good from start to finish! 

Thanks as always. More updates coming 

These types of issues are hard to track down.  
That corroded ground you found under the carpeting is a common culprit to slow and weak electric windows on XT's - I assume you're going to clean that up but just in case , others have had to track that same ground before to remedy flakey devices not working properly.  Johninky is a member here and I know he's seen it and talked about it before for XT's. 

[davepak]

1 hour ago, idosubaru said:

These types of issues are hard to track down.  
That corroded ground you found under the carpeting is a common culprit to slow and weak electric windows on XT's - I assume you're going to clean that up but just in case , others have had to track that same ground before to remedy flakey devices not working properly.  Johninky is a member here and I know he's seen it and talked about it before for XT's. 

I'm just about to start working on it . And I will clean up that ground point. Even though my car has no power windows. Well it has the wiring but no motors. Just regular cranking 

[davepak]

** Sad update **

After trying the result wasn't good. The car started for some time but then Harness on Injector #4 SMOKED. Injector #4 is now leaking the pressure of the fuel pump. The car died. I tried again and then I heard an awful clank from the engine. I tried a few times and now it won't start, actually, it won't turn. Maybe a valve? Maybe I'm actually not sure. I might be declaring this project a totally fried XT. 

 

[el_freddo]

If that injector is squirting that amount of fuel, you might have a cylinder full of fuel that can cause a hydro lock situation. Hopefully not. 

Your oil will probably smell like fuel now. 

Have you swapped injector 4 for a known good unit? I’d start there. 

Also, these injectors are batch fired, what are the paired units? I don’t fully understand how that system works and what’s involved but understand the principal of batch firing. I would’ve thought you’d find two wires from the injectors to the ECU connected. 

Just putting it out there, hopefully not a red herring as I don’t play much with EA82 EFI these days, just EJ22 looms and conversions. 

Cheers 

Bennie

 

[davepak]

24 minutes ago, el_freddo said:

If that injector is squirting that amount of fuel, you might have a cylinder full of fuel that can cause a hydro lock situation. Hopefully not. 

Your oil will probably smell like fuel now. 

Have you swapped injector 4 for a known good unit? I’d start there. 

Also, these injectors are batch fired, what are the paired units? I don’t fully understand how that system works and what’s involved but understand the principal of batch firing. I would’ve thought you’d find two wires from the injectors to the ECU connected. 

Just putting it out there, hopefully not a red herring as I don’t play much with EA82 EFI these days, just EJ22 looms and conversions. 

Cheers 

Bennie

 

Oh well. I'm not sure now what would be the next step. 

I'm guessing I'd remove the spark plug and injector #4 (the offending one) and say, try to turn the engine over and see if there is  /fuel/gas/oil mixture  coming out that might have been trapped. I had swapped the injector for a working one. But I'm afraid there must have been something that went wrong on the test. I had isolated the wires that fire injectors #3 and #4 which were known to be "touching" each other. In attempting this, I realized I had cut the original wire #3 (isolating it) but did not cut wire #4 (not isolating it) this meant the bypassing of this 2 wires was not totally effective. Additionally I used a different ECU sourced from a junkyard. This ECU is for an 87 GL turbo MPFI. It has the same plug connectors and an ADDITIONAL plug connector. I opened it and it is really different from the stock ECU for my 86 XT. Still, I tried it and the car ran. Here, the collection of errors appeared :

The car actually ran and it sounded smooth 

At one point it was rough and it died. 

Injector #4 was full of smoke which then I saw it had to do with a lot of heat on the injector harness and leaking a lot of fuel. What a hazard gosh.. 

Then I disconnected injector #4 as I have done before and tried to start the car. At this point 2 things happened: The fuel pump runs continuously when ignition is offand it stops priming when key is in ON position. The engine turned a few times then emitted a loud clank and it wouldn't turn over. This is where I am at the moment. Thinking that all these attempts might have ruined the engine. 

An interesting thing : I plugged in the old ECU that I repaired with soldering (put some components from the other ECU as an attempt to salvage it). This ECU does not work properly but the LED for trouble codes worked. And I saw a long pulse and 2 short pulses. I believe this is Trouble Code 12. 

I have attached images of both ECU. I'm wondering whether this different ECU might have something to do with the car not firing up properly somehow now? 

This is turning out to be beyond what I expected with this car :-(

 

[idosubaru]

14 hours ago, davepak said:

** Sad update **

After trying the result wasn't good. The car started for some time but then Harness on Injector #4 SMOKED. Injector #4 is now leaking the pressure of the fuel pump. The car died. I tried again and then I heard an awful clank from the engine. I tried a few times and now it won't start, actually, it won't turn. Maybe a valve? Maybe I'm actually not sure. I might be declaring this project a totally fried XT. 

 

Holy smokes.  This is nuts, sounds like a British car.  convert it to carburetor - get an EA82 carb intake and swap it out. it would run and avoid all electrical issues  

Sounds like bleeding injector filled the cylinder with gas and it’s hydrolocked. It’ll probably drain over night or pull a plug and blow/draw the fuel out. 

have you swapped injectors?  I wonder if you should try 4 other injectors or swap the pairs that fire together.  I forget which ones fire together but if 1-3 and 2-4 fire together then swap those pairs and see if your issues “move” from cylinder 3 pair to the other pair. This would verify the injector without needing to buy anything except the incinerated one 

I’m not sure why this happened but maybe the injectors don’t make a perfectly straight run from the ECU to the injectors?

I think the the next step would be tracing that wiring to exactly where it failed. Expose a piece of the wiring by cutting back the wire insulation and exposing the wire but not cutting the wire. Do this at a random point like inside the cabin.  Then test from there to ECU and there to engine to see which side it’s on.   Then do the same thing - test from under the dash to the engine and under dash to previous exposure. 

Seats pulled and you have the testing equipment - this would only take a few minutes.  
 

But the one down side might be that maybe the overheating injector ruined the wiring and the wiring isn’t the causative issue.

does anyone know what all is a part of the injector circuit?

[idosubaru]

If too much damage wasn’t done I’d try to trace and repair the smaller patch of wire you can like I described above.  I don’t understand the injector wiring enough to know if it’s a straight shot from ECU to injector so I wouldn’t Want to run dedicated wires.  I’d rather find exactly where it failed. 

once you do - you may learn something else very important.  Like:

1. other wires are also failed. (I’ve had this happen before when tracing bad wires - rodents chew through some wires and partially through others, broken wires from movement/prior repair work, etc)

2. It was caused by a crack or corrsoion or rodent damage so wiring is probably the issue (ive found this before too)

3. it’s all brown and melted therefore something else might be causing the circuit to overheat.  This would be the most complicated and least helpful but I also think it’s the least likely of these three scenarios. 

[davepak]

*** update ***

So I decided to check what was the damage. It seems it's recoverable. I removed spark plug and injector #4 and turn the crankshaft pulley by hand. Expectedly there was a lot of fuel flooding the cylinder. After a few turns, I removed the fuel hoses, the ECU (although it's dead) and cranked the car with the ignition. The engine turned and it seems it cleaned all remaining fuel. 

Second finding and most mysterious : the wires for injectors #3 and #4 are not "touching each other / or peeled along the way to the injector harnesses. They are fine. But instead, they are showing continuity right from the ECU. The ECU is "shorting" them. I couldn't see this as I had no way to test through the plug (nor I thought this could be the case) but now that I have 2 t-taps attached to these wires I can test and see this. Curiously it is something happening with both fried ECUs and even the third GL-10 MPFI ECU I sourced 1 day ago. All three ECUs are taking injector #3 and #4 signal and putting them together. I have just now traced injectors #1 and #2 and there is no conductivity in between them, I get no Ohms.

Now that's really a strange thing! 

I will try to get another ECU though, as the latest one doesn't work with this car. It seems way "newer" and when I plug it in now it runs the fuel pump right away. It's clearly newer, it's for an 87 GL-10 and my car is an 86 XT. 

Picture 1 shows cylinder #4 after purging the flooded fuel. 

Picture 2 shows no continuity between ECU signals for injectors #3 and #4 so long the ECU is not plugged in. This happens with the dedicated wires and the stock wires for those injectors. 

Picture 3 shows the same wires, but this time the ECU is plugged in. Once again, all 3 ECUs were plugged in and the same results came out. Injectors #1 and #2 did not show these results. 

I'm in the dark here.. 

Scratching my head! 

 

 

 

 

Edited February 2, 2021 by davepak
grammar check

[john in KY]

Is there anything that looks like an old Mopar ballast resistor over by the air filter?  I can't recall if it was the XT or XT6 that used it but am sure one of them for sure.