Injectors 2 & 3 not firing.... wtf? RESOLVED: ECU

[free5ty1e]

EDIT: RESOLVED 6/7/2013 -- it was my ECU. Swapped in a spare turbo manual ECU from my '91 (since it's getting a WRX engine soon anyway) and BAM! Fired right up.
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So, I took my car in this Monday to have the timing belt, tensioner, idlers, water pump, oil pump, cam / crank seals, and thermostat replaced. (side note: timing belt was about to let go! Teeth ripping off, all cracked to hell... I did this just in time!)

It took an extra couple days because:
1) My water pump on this '94 is apparently the WRX pump. I had thought only the pre-facelift Legacies got the WRX pump. So did my mechanic; so we had to wait for the right part to come in.
2) The helicoil repair that my friend and I did several years back (see thread: http://bbs.legacycentral.org/viewtopic. ... 4&p=103662, 6 posts down) was not going to be good for another timing belt service interval; the 2nd helicoil was skewing the bolt as it went in. Luckily, the destroyed bolt hole I thought was part of the block is actually just a part of a bracket that we could replace! So, he got a replacement from Subaru and installed it. Sweet! Ran about $130 for this bracket replacement (for the tensioner bolt hole). I can ask him for a part # if anyone is interested.
3) He had it all together this morning and ready to go, except that for some strange reason - Injectors #2 and #3 are not getting any pulse width whatsoever.
a) Injectors #1 and #4 are receiving pulse width; cylinders #2 and #3 are just flooding out.
b) All 4 cylinders are getting spark
c) He has gone back in and verified that the timing is all correct. He knows Subarus and I tend to believe him on this point.

He says that the PCM (ECU?) grounds the circuit as it signals the injector pulse (I believe this is what he said, I'm terrible at deciphering my own notes lol). The left cam has a gear for the cam sensor on the back of it; does the right cam gear have anything with regards to the cam sensor?
He mentioned that, typically, the cam sensor will control spark and the crank sensor will control injector pulse width (or vice versa).

I'm wondering, does anyone have experience with this sort of thing? Can someone shed light on this situation? I think I'm racking up many more charges as he troubleshoots and I'd like to provide some helpful insight to possibly reduce said expenses.

Any idea if the cam or crank sensor is responsible for our injector pulse control? Or any other ideas? Car was running just fine before the timing operation... but if a sensor has gone bad for some reason I gotta have it replaced...


Thanks in advance!

[Legacy777]

Both the crank & cam sensors determine what the ECU is going to do with spark & fuel. I do not believe one just handles spark and one handles fueling....it just doesn't work that way.

If you have 12v at the injectors and they are opening and flooding the cylinders, I'd check for a shorted wire on the injector leads going to the ECU. Check for continuity between ground and the injector wiring? If you have continuity, disconnect the ECU connector and see if you still have continuity. If you do, you know it's a wiring issue. If you don't, I'd say something in the ECU fried/shorted to ground.

[free5ty1e]

Thanks Josh. I just spent an hour at the mechanics place trying to assist but we came up with nothing so far.

Pulled ecu codes...no idea how long its been since ive cleared them and my poor old laptop I had set up with vikash's dos subaru monitor tool is dead. Anyway we got 14, 23, 41, and 49.

14 is injector 1....probably from when mechanic pulled it to test?

23 and 49 indicate the ecu is pissed off at the airflow sensor for some reason, or was at one point.

Indicates a a faulty learning curve function. Huh... wtf do I make of this?

Ill pass your info along to the mechanic tomorrow Josh. ...thanks again and I will be sure to post results here once I have any.

[free5ty1e]

Hey... ive got a good 91 turbo manual ecu...is it swappable with my 94 you think?

[Legacy777]

Yes, all the turbo Legacy ECU's are compatible.

I would suggest checking the wiring first.....if for some reason the wiring grounded out and fried something in the ECU, you don't want to fry another ECU because of bad wiring.

[free5ty1e]

Excellent - thanks! And yeah a good point - I'm actually suspecting at this point that perhaps he used the arrows on the crank and/or cams instead of the notches to match timing markings. I should have some answers soon. I'm really hoping I don't have a fried ECU but at least I do have a spare if it is the case.

Also, he took photos of every step and left it really cleaned-up in there... once I get my hands on the images I'll post 'em up. The front of my engine looks WAY newer than the rear... lol

[free5ty1e]

How lame; my ECU was the issue. After confirming continuity between injector wiring and ECU, swapped in the '91 ECU and it fired right up. Luckily I had this spare handy!

I'll be picking it back up after work today, woot! Then I can drop off the '92 autotragic and get some really clicky CV joints replaced, for starters... that poor car needs some TLC now too. The fact that it is still kickin' is a testament to how tough these cars are -- it was beat on for several years as I let my father use it as his main car, and he just could not be bothered with maintenance or even addressing obvious issues (such as the front driverside brake caliper coming loose and chewing its way partially through the rim).

Anyway -- he got some photos of the timing belt operation as it was in progress, he really cleaned it up in there (just imagine it was completely coated in grimy oil all over before; I believe I've cost this guy several cans of Brakleen at this point, lol):

[Legacy777]

Glad you got it fixed. I'm curious how it worked before you brought it in and then the ECU stopped working???

[free5ty1e]

Was running great... the only indication I had that I may need a timing belt soon was the car began requiring 4 revolutions before it would start up....I was used to it only taking 1 or 2 revolutions to start up. I still am concerned and plan to go over my wiring this weekend to see if I can find any potential causes of a short or something. Thats all I need is for the same issue (whatever it is) to fry my spare ecu...

Sent from my SAMSUNG-SGH-I337 using Tapatalk 4 Beta

[free5ty1e]

2) The helicoil repair that my friend and I did several years back (see thread: http://bbs.legacycentral.org/viewtopic. ... 4&p=103662, 6 posts down) was not going to be good for another timing belt service interval; the 2nd helicoil was skewing the bolt as it went in. Luckily, the destroyed bolt hole I thought was part of the block is actually just a part of a bracket that we could replace! So, he got a replacement from Subaru and installed it. Sweet! Ran about $130 for this bracket replacement (for the tensioner bolt hole). I can ask him for a part # if anyone is interested.

Well, I don't care if anyone is interested or not, since it happened to me I'm documenting this replacement tensioner bracket Subaru OEM part number right here and in the above-referenced thread for future reference:

Tensioner Bracket (includes tensioner's bolt hole that I had to helicoil at one point): Subaru Part # 13086AA012

[Legacy777]

Thanks for sharing