Resolved 1G Car still wont start after ECU replacement?

[tbird]

Have been having troubles getting the car to start I think I have narrowed it down to spark but I'm not sure.

91 TSI

Right now I borrowed my friend 90 ECU, swapped the 2 wires, cranks and once in a while ill get a pop like when I very first hit the key but that's it. I replaced the coil didn't help. I did notice on my SAFC and by watching the spark plugs it only sparks like 1 time when I first hit the key then I get nothing?

On the SAFC when it first starts cranking it'll jump up rpms then after like 1 second it goes to 0 and doesn't move? Does this sound like CAS? Another faulty computer? Power transistor?

Hmm, okay I just went and pulled a plug and laid it on the valve cover while cranking and it seemed to spark ok and keep sparking. Plugs seemed a little wet put new plugs in still no start. What could it be?

One last question is there a way to test the power transistor?
Will one from a 1990 plug into a 91 harness?
And is there a way to turn the fuel pump on constant to make sure that's not my problem.

 

[gofer]

Turn the key to the "ON" position without cranking it, does the CEL illuminate for 5 seconds and then disappear? If it doesn't illuminate at all you've got a bad ECU, if it stays lit then you've got a code that you need to scan.

Checking spark on one cylinder won't tell you anything except that one cylinders getting spark. At the least check spark at 4 & 2 or 1 & 3 so you can eliminate the possibility of it being a bad CAS, coil pack, and power transistor.

Checking fuel is easy and the only way you can activate it manually is with DSMLink, which you don't have. To make sure fuel is making it to the fuel rail just disconnect the fuel line that connects to the rail, coming off the fuel filter. Be sure to have a decent size cup ready that you don't mind throwing away and have someone crank the car. If the fuel pumps working fuel should pump out of the line into the cup, just be careful because it comes out fast.

If all the checks good its time to check timing, your timing belt could have possibly skipped a few teeth.

 

[tbird]

CE light comes on for 5 seconds then goes out.... I will try the other posabilities today thanks

 

[asb2106]

is it timed properly?

I "thought" I had mine timed right, ended up being off 180 degrees on the intake cam. I would get the occasional pop like it was going to start, the occasional back fire, and nothing.

 

[BlackMount]

+1 on the 180.

Are you 100% sure its a Turbo ECU you borrowed?

Did your friends DSM run fine with it? Did your DSM run fine with previous ECU? Otherwise its gotta be timing like 180 out.

 

[tbird]

Well the thing why I say it is, because when I got it, I got it started one time. It ran like total crap when it was cold and if I gave it any gas at all it would die, I would have to like flutter the gas to keep it running then after about 10 minutes it smoothed out some what and I was able to drive it around the block but after I turned it off it never ran again.

I'll flip the CAS after I know I got fuel.

Yeah the ECU is reman ECU from a friend his car ran perfect before he pulled it apart.

 

[BlackMount]

Is there any CEL's?

 

[tbird]

how can i tell if the cars not running? just key on and wait for flashing cel?

 

[BlackMount]

get a analog voltmeter or a 12v buzzer from radioshack.

run it on the 2 terminals for the OBD and count the pulses.

If it's a constant pulse that doe's not change then the ecu is working normally.

 

[tbird]

well I have fuel.... pull the return line and cranked it and fuel comes out like it should.

I hooked a test light to it and it just pulses on and off forever.... so im guessing ecu is outa the question

turbo ecu wouldnt even matter would it?

Flipped the cas still nothing... gonna try a power tr today if a 90 will work in a 91... and maybe grab another ecu and cas

 

[steve]

gonna try a power tr today if a 90 will work in a 91.

It won't. The connectors are different due to the different number of pins to support the tach output on the 91+ PTM.

 

[tbird]

well that sucks.

what about the cas?

 

[steve]

Nope, 90 CAS has a different connector too.
Many of these differences between 90's and 91+ cars are well documented here.

Same can be said for the diagnostic procedures for checking the PTM, CAS, coils, etc. Many of them are under the TECH menu above. There is also a checklist for no starts. http://www.dsmtuners.com/forums/articles-miscellaneous/217951-how-diagnose-no-start.html

 

[BlackMount]

well I have fuel.... pull the return line and cranked it and fuel comes out like it should.

I hooked a test light to it and it just pulses on and off forever.... so im guessing ecu is outa the question

turbo ecu wouldnt even matter would it?

Flipped the cas still nothing... gonna try a power tr today if a 90 will work in a 91... and maybe grab another ecu and cas

Yes, using a turbo ECU in a non turbo car or vice versa will result in problems.

When you swapped the pins for the 90 ECU out did you also swap the power transistor, I think you might have over looked that.

And your timing itself not the CAS can still be 180 out.

 

[asb2106]

timing

(from vfaq)

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check to make sure your two dowel pins are pointing up

 

[BlackMount]

timing

(from vfaq)

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check to make sure your two dowel pins are pointing up

wont help if your 180 out.

180 out your timing can be dead on, your just set on the wrong stroke.

 

[tbird]

nah thats not the problem the car used to drive fine... I replaced the head a couple of times... it jsut died one day and started to get harder and harder to start..... can anyone tell me how to test my power tr unit. or wire in a 90 on a 91 harness I have a plug also have a 90 cas and 90 plug

 

[asb2106]

wont help if your 180 out.

180 out your timing can be dead on, your just set on the wrong stroke.

yah man it sure will.

If the dowel pins are straight up theres no chance your 180 out.

Think about it... theres only 1 dowel pin on each cam sprocket.. when you have it properly timed those 2 will be straight up. This will result in that happening each and every time.

Or look at the teeth, for the exhaust side you want the mark on the tooth in the middle, for the intake side you want the mark inbetween teeth to the middle.

Either way you do it the dowel pins point up

 

[tbird]

Hey I got a 90 power transistor but it has different pins. Can anyone tell me how to wire a 90 power transistor and coil pack into my 91 harness? I just also tried a 3rd 91 TSi ECU and same thing. I smell fuel so its gotta be spark.

So, I pulled my stock power transistor off just now and noticed its cracked. So I gaurentee water got in it and fried it. HOPEFULLY!!! I have a 90 here just need to know how to wire it up.

 

[steve]

If the dowel pins are straight up theres no chance your 180 out.

What your forgetting is that you can install the CAS two ways, one of which is wrong. It's then 180 cam degrees or 360 degrees at the crank putting the timing events on the wrong stroke. While that's not a big deal for the ignition due to the wasted spark firing each plug every 360 degrees but it is an issue for the injector timing.

 

[SpawnedX]

There is one thing I don't see any mention of...it's a thought, don't crucify me, but your injector resistor box could be bad.

You may get fuel to the rail, but if the injectors aren't pulsing it's not getting to the motor.

 

[tbird]

So can anyone please help me wire in a 90 power transistor and how can I test the resistor pack that's another impossible part to get locally?

 

[BlackMount]

yah man it sure will.

If the dowel pins are straight up theres no chance your 180 out.

Think about it... theres only 1 dowel pin on each cam sprocket.. when you have it properly timed those 2 will be straight up. This will result in that happening each and every time.

Or look at the teeth, for the exhaust side you want the mark on the tooth in the middle, for the intake side you want the mark inbetween teeth to the middle.

Either way you do it the dowel pins point up

all The tiiming marks and clues and hints such as the dowel pins can be 100% correct and still be 180 out. it is not a matter of timing not lined up right. it is a matter of head is attempting to match a stroke the the block isn't on.

Speaking from experience here.

Basically

The head will be on the Compression Stroke, and the Block will be on the Exhaust Stroke. (don't know if those are the right stroke names but you get the idea)

Crank turns 2 times for every 1 time the cam turns.

 

[tbird]

Steve, do you know how to wire in a 90 power transistor? You seem to be god on here with ECU crap

I think I may have it figured out. Only question is running the 90 coil pack and transistor on a 91 harness. Will the tach wire from the coil now wire into the harness white wire that goes to the ECU? And will the +12v from the harness go into the coil pack now instead of the power transistor?

Maybe I need to draw this up

 

[BlackMount]

Steve, do you know how to wire in a 90 power transistor? You seem to be god on here with ECU crap

I think I may have it figured out. Only question is running the 90 coil pack and transistor on a 91 harness. Will the tach wire from the coil now wire into the harness white wire that goes to the ECU? And will the +12v from the harness go into the coil pack now instead of the power transistor?

Maybe I need to draw this up

SEARCH!!!!
There is a How-To\Tech Article\(VFAQ) on using a 91-94 ECU in a 90 DSM or 90 ECU on a 91-94 DSM that includes information about the power transistor.