1990 ECU in a 1991

[Skillz]

Hey, I've read the VFAQ about this topic, but it only tells how to put a 1991 in a 1990, and that it's possible to do this; however it doesn't say if a 1990 ECU will work in a 1991 car.

This is my problem. My car suddenly died while giving her a test drive after installing a stainless steel oil feed line on my turbo. Well, to make a long story short I took the oil filter bracket off, and sent it to a machine shop so they could take that inverted bolt out, when I got it back, I put it back on my car, hand tighten the oil filter, filled her with oil and went driving. Well, little did I know, they removed the oil cooler from the oil bracket when I gave it to them, and never tightened that bolt back up. Now, it all appeared to be on tight, when I hand tightened it, but that bolt came undone while driving around. Needless to say, all my oil came out of my engine, and all over the side of my car. I was going about 35ish when my car suddenly just died on me. All attempts to start it again failed. (I was stuck on a long bridge, at night, so I couldn't tell what the problem was.) Well, I got someone to push me off the bridge, and that's when I seen the oil was gone from my engine.

So I got my cousin to tow me back home, where I tightened that bolt. However, since then my car will NOT start. I figured it was the ECU, after doing some diagonistics. The engine turns over good when I try to start it. (Not too "freely" either) so I am sure I still have good pressure in the cylinders. I took apart my ECU, and I noticed the caps had leaked all over the board. I got a 1990 ECU from my cousin, that was workin just before we took it out of his car, but my car still will not start.

Any clues?

 

[headrec*]

From the sound of it the lack of oil cause the engine to bind up (I could be wrong). That would be why it isn't turning over freely and ultimately not starting.

 

[Skillz]

Thanks for the reply man, but I think you mis read my original post.

I said the engine is turning over, but NOT TOO freely. Just as it always has. So I doubt the engine has locked up. I am going to take off the timing belt cover and observe that later today.

 

[headrec*]

Sorry when you said not freely I thought you ment things were binding up and that could have been due to no oil.

 

[oldman]

You can switch a 90 into a 91 by switching a couple of wires but not vise versa.

 

[Skillz]

So I can put a 1990 ECU in a 1991+ car, by switching a couple of wires?

I know for a FACT that I have placed a 1991+ ECU in a 1990 Front Wheel Drive Turbo Eclipse, and it worked. Only problem was it didn't read the correct sensors and what not. (Such as the RPMs only reading like 2k or 3k RPMs, when I know it should be alot higher than that.)

headred*, don't worry about it bro. I should have been a little more specific on what I had said, but I knew you misunderstood me. Thanks for the prompt reply though.

 

[oldman]

So I can put a 1990 ECU in a 1991+ car, by switching a couple of wires?

I know for a FACT that I have placed a 1991+ ECU in a 1990 Front Wheel Drive Turbo Eclipse, and it worked. Only problem was it didn't read the correct sensors and what not. (Such as the RPMs only reading like 2k or 3k RPMs, when I know it should be alot higher than that.)

headred*, don't worry about it bro. I should have been a little more specific on what I had said, but I knew you misunderstood me. Thanks for the prompt reply though.

That is why a 91-94 will not work properly because wirings are different for some sensors and the tach will not work. Can you imagine driving without the tach? I do know for sure 90 ECUs will work on 91-94 cars by switching two wires, I just don't remember which two.

 

[Skillz]

Hey, thanks man!

I do have one question though. I think I know which two wires I need to "switch" but I think I have to cut the wireing harness to do this, and I don't want to.

I have one other question though. Will the car NOT crank at all until you switch those two wires? If so, then that will explain why the car still isn't cranking, and I will go ahead and purchase a 91+ ECU.

Thanks for your time bro.

Oh, and driving without a Tach isn't too hard. Just shifrt according to sound. However, the engine does weird shit when it doesn't know what RPMs its at. hahahaha

 

[adidas_coin]

Stop me if i read this wrong, but you ran your car out of oil and you think your ECU is fried? have you tried a noid light yet?

 

[Skillz]

noid light? Do tell.

If it matters, I do not think my engine is harmed in anyway, due to the lack of oil for that very short period of time.

I also do not think that the lack of oil in my car had anything to do with my ECU, but I do belive my ECU is bad. Simply because, I have had a similar problem before, only .. the car would actually crank, but it wouldn't stay running very long. I think I figured once the ECU warmed up a little, it would shut off or something.

Anyway, I have no idea what a noid light is, or what it does.

 

[oldman]

Hey, thanks man!

I do have one question though. I think I know which two wires I need to "switch" but I think I have to cut the wireing harness to do this, and I don't want to.

I have one other question though. Will the car NOT crank at all until you switch those two wires? If so, then that will explain why the car still isn't cranking, and I will go ahead and purchase a 91+ ECU.

Thanks for your time bro.

Oh, and driving without a Tach isn't too hard. Just shifrt according to sound. However, the engine does weird shit when it doesn't know what RPMs its at. hahahaha

Just make sure you don't go anyway near the redline without tach. I can't think of any other way but to cut the wire. I can't remember what those two wires are for so I can't help you as to wether it will crank. If you don't get an answer here pm steve on this board, he will be able to answer it for you. He can probably fix yur old ECU as well. Good luck.

 

[steve]

Hey, thanks man!

I do have one question though. I think I know which two wires I need to "switch" but I think I have to cut the wireing harness to do this, and I don't want to.

I have one other question though. Will the car NOT crank at all until you switch those two wires? If so, then that will explain why the car still isn't cranking, and I will go ahead and purchase a 91+ ECU.

The pins are 6 and 14. You don't cut anything. The pins pop right out of the connector with a small jewlers screwdriver to release the retainer.

The car not cranking doesn't have anything to do with the ECU. The starter circuit and the ECU are independant. The car will start with the pins not swapped but it will run poorly since thse pins are for the IPS and the reset line for the MAF.

Steve

 

[adidas_coin]

Go to Radioshack and get a 12 volt l.e.d. its like $1.69, on our cars you shouldnt need a resistor, unplug an injector and put the led in its place (plug it into the injector plug) and have someone watch it while you crank, if it lights then the ECM is grounding the injectors like it should, have you replaced the capacitors in the ecu yet? might want to check those too, if there bad theres a 50/50 chance so is your ECM, since they are responsible for signal filtering.

 

[adidas_coin]

BTW by "our cars" i meant the 1g's, i forgot my 2nd gen is listed under my primary car.

 

[Skillz]

I have a volt meter, can I just use that instead?

I do not belive this ECU has had the caps replaced yet, but I know it was working when we removed it from my cousins car.

So the car not cranking is not a sign of the ECU being bad?

I will run those tests later tonight, or tomorrow. Thanks for the replies guys.

 

[steve]

I have a volt meter, can I just use that instead?

Yes. it's a little harder to read the codes with digital voltmeter but it can be done.

So the car not cranking is not a sign of the ECU being bad?

Right, the ECU doesn't control the starter.

Steve

 

[adidas_coin]

If you are talking about using a volt meter in place of a l.e.d you could assuming you have a high impedance digital meter (Analog will run the risk of frying the ECM) the voltmeter will tell you if the injector is being triggered or not. making a noid light for futer use is never a bad idea though. be sure to ignore the voltage readings though, as voltmeters average voltage, so if it doesnt read bat voltage dont be alarmed. there is a reason why injectors are scoped, meters are the tool, but just to see if the ECM is grounding them, it will do.

 

[adidas_coin]

Have we done compression and Cylinder leakdown tests on the motor yet. also do a starter current draw test,higher the amperage usually higher the mechanical resistance. also try turning it by hand once, see how hard it is.

 

[adidas_coin]

Yes. it's a little harder to read the codes with digital voltmeter but it can be done.

Right, the ECU doesn't control the starter.

Steve

i thought we were checking the ecm? iono, im half asleep.

 

[Skillz]

Hey guys, I did some thinking at work today, and I think I may have the problem solved.

I have a Walbro 255l fuel pump, re wired with a relay in my car. I have not checked to see if my car is getting fuel, and when I crank the car, I don't recall hearing it. So I am thinking I am not getting any fuel. When my cousin gets off, I am gonna have him crank the car, while I test the fuel pump to see if it is working or not.

I know the relay went out before, it melted. Had to pay like $4 to get a new one. I will do all those tests you guys recommended and get back with you.

Thanks again.

 

[oldman]

Damn it, you mean after all this you have not check for fuel yet.

 

[adidas_coin]

Damn it, you mean after all this you have not check for fuel yet.

Wow!!! im with this guy, always check the basice 1st, spark and fuel. also i dont know how the injector/ecm test went yet. so if you got nothing the EFI fuse located just off the bat. and again.......wow.

 

[DSM PERFORMANCE]

You can put 1990 ecu in a 91-94 car by switching pin #6 & #14 (as somebody said) but to put a 91-94 ecu in a 90 car is more complicate : you need to change pins #6 &#14 AND it work but the tach doesn't, what you need to do is change the coils pack, the transitor and the gauge console (or just the tach) all from a 91-94 car. And it will work.

 

[steve]

to put a 91-94 ecu in a 90 car is more complicated

That's nice but since the thread starter has a '91 what has that to do with the question?

Steve

 

[DSM PERFORMANCE]

That's nice but since the thread starter has a '91 what has that to do with the question?

Steve

Just for the info, because almost all people think you can do it vice-versa, if you do a search it's often said that you can put a ecu 91-94 in a 90 by only switching pin 6 & 14 (in a lot of board) and I wanted to let people know that you need more then that...