No spark,tested every every thing.

[74runner]

Hey guy's I have a 1991 AWD Turbo Eagle Talon with a "no spark issue"

I have swapped out the tsu, coil and repaired the coolant wires/connectors and the light went out
I do NOT have spark on any coil.

The 20amp motor fuse at the battery is good and so are all the other fuses.
When watching the dash (key on) the check engine light does not do it's normal test light up and the boost gauge does not move so I'm guessing the ECU has a blown sensor ground. Before I pull the ecu can anyone point to any thing I might have missed. CAS or ?

I should point out the car was sitting for a few years before I bought it. I cleaned the fuel system and tank and installed a new fuel pump, the car is bone stock with 122000km/s with a fresh tune up and new fluids.I forced a good ground using booster cables on various points in the engine bay to help rule out bad grounds.
I don't have the funky smell you get from bad ecu caps either.

 

[19Eclipse90]

Repair the ECU. If it does not work correctly or at all, nothing exciting is going to happen and we are wasting our time trying to help you diagnose anything else.

 

[74runner]

Repair the ECU. If it does not work correctly or at all, nothing exciting is going to happen and we are wasting our time trying to help you diagnose anything else.

Like I said, "I'm guessing it's the ecu" I'm looking for someone with skill and useful info before I pull the ecu for no reason, who knows someone might actually tell me what to look for on the ecu that could be the cause, some thing I might over look. Honestly I've never been on a forum with such blow off answers.

 

[codym]

Like I said, "I'm guessing it's the ecu" I'm looking for someone with skill and useful info before I pull the ecu for no reason, who knows someone might actually tell me what to look for on the ecu that could be the cause, some thing I might over look. Honestly I've never been on a forum with such blow off answers.

If you are guessing it's the ECU, than why are you second guessing a member who is obviously very knowledgeable? The ECU takes 5min to check, if that. You're not going to smell or see anything wrong with it through the cover. Take the ECU out, and inspect it.

It might look perfectly fine, and it could still be bad.


If the ECU is not the issue, than yes, the CAS sensor could be. If it is unplugged or bad, it will not allow the car to start because the ignition doesn't know when to fire.

 

[19Eclipse90]

Not every issue with your ECU can be seen with the naked eye. Ask me how I know.

But okay, the check engine light not coming on for 5 seconds and the boost gauge not going to zero means the ECU is not powering up. If the ECU does not power up, you will not get spark.

Here's what you can look at, from http://www.dsmtuners.com/forums/articles-tuning-ecu/435961-1g-basic-ecu-mpi-circuit-function.html...

The first thing you should do if your ECU doesn't power up (CEL on for about 5 seconds, the boost gauge displays 0) is check the two fusible links (MPI fuse and IGN fuse on the positive battery terminal) and the room fuse (that's fuse 19). Measure the fuses for continuity (0 ohms resistance) rather than look at them since looking isn't an accurate test. Then check for battery voltage at the ECU and MPI relay pins. Remember that the ECU doesn't get power on pins 102 and 107 until the MPI relay is activated by turning the ignition key to RUN or START. If the MPI relay doesn't activate try grounding its pin 8 and check that power shows up on its pins 4 and 5. If that works then either the ECU isn't seeing the IG1 signal or the ECU is damaged.

If battery voltage is present on ECU pins 102/107, 103, the ECU grounds are good, and the ECU still doesn't power up it's likely damaged.

Cheers.

 

[74runner]

Sorry guy's had a bad week, my step son was diagnosed with schizophrenia and I'm a little on edge. I took your advice and pulled the ecm, it looks fine but I swapped it with one I had rebuild a few years ago. I now have boost gauge movement but still no engine light. I checked a video I made when I first started the car up to see if the light had worked then and it did. The car has sat for 1 month since then so I think it's safe to say the engine light bulb is still good.

Oh, still no spark or new symptoms.

 

[1G Eclipse94928]

Sorry guy's had a bad week, my step son was diagnosed with schizophrenia and I'm a little on edge. I took your advice and pulled the ecm, it looks fine but I swapped it with one I had rebuild a few years ago. I now have boost gauge movement but still no engine light. I checked a video I made when I first started the car up to see if the light had worked then and it did. The car has sat for 1 month since then so I think it's safe to say the engine light bulb is still good.

Oh, still no spark or new symptoms.

It sounds like you know the whole ignition system, and you say you "tested every every thing", well you didn't check the cas which is a main failure point??... then there's the power transistor. Can you confirm you tested everything really?

 

[74runner]

It sounds like you know the whole ignition system, and you say you "tested every every thing", well you didn't check the cas which is a main failure point??... then there's the power transistor. Can you confirm you tested everything really?

I've owned 8 DSM's over the years and currently own 2 now so I've learned a ton over the years. I skipped off and went to muscle cars for a while so I've gotten rusty in the ways of the DSM. I posted for help in the hopes that you guys will point out what I might have missed. I'll check the CAS tomorrow, I just didn't feel it was to blame due to the CEL and boost gauge not working properly.
I didn't feel like testing the PT so I swapped it out for another one and then another one after it didn't help .

 

[codym]

If the ECU is not the issue, than yes, the CAS sensor could be. If it is unplugged or bad, it will not allow the car to start because the ignition doesn't know when to fire.

Definitely something to verify, before I learned to be more organized and make notes I would often forget to plug back in either the CAS or MAF, they like to jump into small dark spots when working on the intake.

 

[74runner]

Definitely something to verify, before I learned to be more organized and make notes I would often forget to plug back in either the CAS or MAF, they like to jump into small dark spots when working on the intake.

I've never known (Or I forgot) a CAS could cause the "cel" and boost gauge not to operate like a blown sensor ground on the ecm does? I'll swap it out for kicks because I have 3 or 4 kicking around and must have at least one good one . I'm going to buy new Caps for the ecu while I'm at it because I can't find my esr meter to test them .

 

[19Eclipse90]

I've never known (Or I forgot) a CAS could cause the "cel" and boost gauge not to operate like a blown sensor ground on the ecm does?

At least to part of your question, it won't. The CAS has nothing to do with the operation of the boost gauge.

Check fuse 11. It is responsible for the power to both the CEL and boost gauge from the ignition switch; it will be labeled "GAUGE" on the interior junction block. They ground through the ECU, pins 64 and 3, respectively. Since you now have the boost gauge working, you might pull your cluster out to check the bulb for the CEL to find out whether it is blown out or not. This takes maybe a half hour to pull and reinstall.

As I mentioned last time, you probably ought to make sure your ECU is powering up (read this: http://www.dsmtuners.com/forums/articles-tuning-ecu/435961-1g-basic-ecu-mpi-circuit-function.html). Once you have that, you can expect things to work if there are no issues with individual components.

 

[74runner]

It won't.

Check fuse 11. It is responsible for the power to both the CEL and boost gauge from the ignition switch; it will be labeled "Gauge" on the interior junction block. They ground through the ECU, pins 64 and 3, respectively. Since you now have the boost gauge working, you might pull your cluster out to check the bulb for the CEL to find out whether it is blown out or not. This takes maybe a half hour to pull and reinstall.

As I mentioned last time, you probably ought to make sure your ECU is powering up (read this: http://www.dsmtuners.com/forums/articles-tuning-ecu/435961-1g-basic-ecu-mpi-circuit-function.html). Once you have that, you can expect things to work if there are no issues with individual components.

I only have a short amount of time each night but hope to have more time this weekend to follow up on you advice. I'll see what I can do tonight

Going out now to check fuse 11 and the MPI.

I checked fuse 11 and got 11.6v, I double checked all the fuses using my multimeter just to be sure and every thing checks out. I also unplugged the CAS and plugged in a spare for kicks and giggles and gave it a spin but didn't get any results from it, but no surprise really.
I pulled the MPI and was going to do some testing but it's cold out side and started raining so I packed it in for tonight......I decided to remove the 3 capacitors from the original ecu and I do now suspect the 16 volt cap of being faulty but with out my esr meter who knows.I'll pick some new caps up on Friday and replace them to be sure.

I'm not sure if this is good luck or bad luck? I have 2 of the 3 Capacitors I need to repair my ecu ....The one I don't have happens to be the 16 volt 100 microfarad cap that I suspect to be bad!!!

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[74runner]

Worked late tonight, no time to play.

 

[luv2rallye]

I'm not sure if this is good luck or bad luck? I have 2 of the 3 Capacitors I need to repair my ecu ....The one I don't have happens to be the 16 volt 100 microfarad cap that I suspect to be bad!!!

Better get 25 volt caps minimum! The alt can sometimes put out 16v not to mention spikes.

 

[74runner]

Better get 25 volt caps minimum! The alt can sometimes put out 16v not to mention spikes.

Thank's, thats what I did on my 90tsi, mostly because they were out of 16v though

 

[brads]

Better get 25 volt caps minimum! The alt can sometimes put out 16v not to mention spikes.

If he is replacing a 16V cap, it is probably OK to use the 16V.

10V-16V is the value I usually see on the 5V side of things inside an ECU. If so, it will never see the 16V spikes from the alternator, unless something else is horribly wrong with the ECU. And at that point, the caps aren't really an issue.

Of course I don't remember exactly which cap value is which, so if that is actually on your 12V power side inside the ECU, even 25V may be a bit low.

 

[74runner]

If he is replacing a 16V cap, it is probably OK to use the 16V.

10V-16V is the value I usually see on the 5V side of things inside an ECU. If so, it will never see the 16V spikes from the alternator, unless something else is horribly wrong with the ECU. And at that point, the caps aren't really an issue.

Of course I don't remember exactly which cap value is which, so if that is actually on your 12V power side inside the ECU, even 25V may be a bit low.

I just replaced all 3 caps, 2 were just starting to leak so there was no visible damage to the board. I put it back into the car and the mpi clicked and the fuel pump runs but the engine light and boost gauge do nothing and still no spark so I put the spare ecu back in and got boost gauge movement but no engine light or spark. I hope to have time to test the mpi this Saturday after noon after work....I replaced the 16v 100uf cap with a 25v 100uf as for the other 2 caps I used the ones I had in stock here....I wanted to point out to any one new reading this that you can up the number of volts on a cap but don't change the uf! (Microfarad) number.

 

[luv2rallye]

Better safe than sorry (using 25v instead of 16v). You don't want to risk blowing out a $700 ECU because your alternator's regulator went out so it's now outputing a steady 18.6 volts (which I've heard happening - just search these forums and you'll see). So it's not just spikes but also failures in other components.

 

[brads]

Better safe than sorry (using 25v instead of 16v). You don't want to risk blowing out a $700 ECU because your alternator's regulator went out so it's now outputing a steady 18.6 volts (which I've heard happening - just search these forums and you'll see). So it's not just spikes but also failures in other components.

If you are trying to make them able to run at 18.6V, you should have the caps sized at 50V. Most places derate the cap by a factor of 2-3x the voltage. 25V rating is still too close.

My point is that the 100uF 16V cap is most likely on the 5V line, or some other lower voltage regulated line inside the ECM. And if it's on a 5V line, 16V cap is fine. If it is on any regulated power inside the ECM, then if it gets blown from being overvoltaged, the cap is not the problem. Your voltage regulator in the ECU is the problem, and it will kill all the other components in short order, so whether the cap dies or not is irrelevant.

 

[74runner]

I've got today off and it's +10 so I'll be out working on the car. I'm sure I'll have some questions for you guys soon .

Ok, pin 10 MPI relay has constant power as it should.

pin 3 has power with key on.

pin 103 has constant power.

pin 110 checks out ok also.

Quick video jumping to pin #1......

https://www.youtube.com/watch?v=LCcDLFXg9ho

 

[luv2rallye]

ECU pin 110 gets power from ignition switch (same as MPI pin 3). But it's used as a signal to start powering up the ECU. This is done by pulling ECU pins 63 and 66 low which activates the MPI relay which supplies main power to the ECU (and other engine sensors) on ECU pins 102 and 107.

 

[74runner]

I continued on to check pins 102 and 107 and they both power up when the MIP powers up and shuts off after a few seconds of turning off the key like they should.

ECU pin 110 gets power from ignition switch (same as MPI pin 3). But it's used as a signal to start powering up the ECU. This is done by pulling ECU pins 63 and 66 low which activates the MPI relay which supplies main power to the ECU (and other engine sensors) on ECU pins 102 and 107.

Ok, thank's! I would have to assume that both ecu's are bad then?

I'm going to check pin 64 with the key on to see if it sends the signal for the cel, don't know why I didn't before ?

Just checked it, no voltage coming out at all.Anyone have any clue as to what component I need to replace on the ecu?

 

[luv2rallye]

Ya it's looking more and more like the ECU. Read paragraphs 7-9 (Shortly after...) to understand ECU operation here: http://www.dsmtuners.com/forums/articles-tuning-ecu/435961-1g-basic-ecu-mpi-circuit-function.html

 

[74runner]

Ya it's looking more and more like the ECU. Read paragraphs 7-9 (Shortly after...) to understand ECU operation here: http://www.dsmtuners.com/forums/articles-tuning-ecu/435961-1g-basic-ecu-mpi-circuit-function.html

Yeah I've been over it 20 times now . Thank's!
I have a 90ecu kicking around that had the caps leak and caused a surface mount cap to come loose. I might try and save some parts from it to bring my 91 back to life.

 

[74runner]

I've decided to look a little deeper into the original ecm (The one thats not powering up at all).........
In the link below it mentions a .1 surface mount decoupling cap but it doesn't say if it's a .1p or .1uf and what volt? I would have to assume it's a .1uf but that could end up in a shorted out board ...Any one know for sure??? I have some .1uf 100v here but I'm not trying them with out more info.(see pic)

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Quote from the link:
"There is plenty of info around the net on the caps, I've noticed there is a small surface mount decoupling cap(C14-removed and circled in the pic) that is usually bad as well, and most info doesn't say anything about this cap.I usually just replace it with a non-surface mount .1 ceramic cap closer the the connector(also circled in the pic)"

http://www.dsmtuners.com/forums/articles-tuning-ecu/116585-troubleshooting-fried-ecu-components.html