My 86 Fiero with 2.8 6-cylinder with a new ECM died. I did have a check engine light for about 4 seconds in key on position but fuel pump did NOT prime, then the check engine light went out. Cranks but obviously no fire without check engine light.
Am I crazy to think that something in the fuel pump wiring is causing issues with the ECM? What can I check to help narrow this down? I don’t understand electricity all that well, dumber is better. I do have a meter, work mechanic showed me how to test for volts so I can see if a circuit is live or not.
Check engine light = OK ECM Fuse = OK Main power feed to ECM = OK, matter of fact ECM was getting warm too. Grounds = OK, very good all around. Fuel pump with a direct power feed through ADL connector = OK, it turns on Fuel pump relay = OK Pick up coil and module should be good otherwise I wouldn’t have got a check engine light for 4-seconds.
Suggestions please??
------------------ jetman Silver 86 SE 2M6 4-speed, with "check wallet light" Now fortified with 8 essential slices of bacon goodness
Likely no because FP power is switch on by FP Relay. (and OP Switch when you get enough Oil Pressure.)
Did you change anything else?
Check ECM "reset" fusible link. Can have corrosion in the connector etc. See my Cave, Fuse Links notes
New ECM is really dead then return it.
(edit to fix cave links) ------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
My 86 Fiero with 2.8 6-cylinder with a new ECM died. I did have a check engine light for about 4 seconds in key on position but fuel pump did NOT prime, then the check engine light went out. Cranks but obviously no fire without check engine light.
Am I crazy to think that something in the fuel pump wiring is causing issues with the ECM? What can I check to help narrow this down? I don’t understand electricity all that well, dumber is better. I do have a meter, work mechanic showed me how to test for volts so I can see if a circuit is live or not.
Check engine light = OK ECM Fuse = OK Main power feed to ECM = OK, matter of fact ECM was getting warm too. Grounds = OK, very good all around. Fuel pump with a direct power feed through ADL connector = OK, it turns on Fuel pump relay = OK Pick up coil and module should be good otherwise I wouldn’t have got a check engine light for 4-seconds.
Suggestions please??
New ECM as in you just installed it in the car, or it's not very old and the car was running fine a couple of days ago and now this?
If you just put it in the car and it's malfunctioning you may have damaged the chip during transfer between the ECMs. If it was in the car working fine initially, turn the key to on and observe the engine light, it should flash twice and stay on steady and should repeat that display each time you power up the car after being off for at least 30 seconds.
If the ECM is bad the likely culprit is short to ground and although a fuel pump can't do it directly the fuel pump relay can if the windings in the relay have have shorted internally greatly reducing the relay coil resistance and overloading the relay driver. That goes for all continuously powered relays; cooling fan, blower motors, A/C compressor.
If you arrive at the conclusion your ECM has failed and it's not likely to be a brand new bad, I believe the easiest way to track down a short to the ECM would be to sit in the car and check grounds, resistances and voltages at the appropriate terminals of the harness ECM plug following the pin assignment for the Fiero ECM.
The last ECM I had fail gave a warning sign first with a spontaneous fuel injector fuse failure, about a week later I could smell the characteristic odor of burning electronics as the car slowed to a halt.
I think there was a guy who's OP sender fuel pump circuit burned his ECM. Don't remember who or the title of the thread, but it was a few years ago. If you suspect the FP relay, by all means replace the ten dollar part. Upgrading to the '88 OP sender seems like another no-brainer, but I still haven't done either of mine.
The last ECM I had fail gave a warning sign first with a spontaneous fuel injector fuse failure, about a week later I could smell the characteristic odor of burning electronics as the car slowed to a halt.
OMG Joe, that's exactly what happened. Fuel injector fuses kept blowing, increasingly quicker after the car was started, then the dreaded crispy burned up smell of a fried ECM
GOOD NEWS!!!
ECM is ok, I got a check engine light, it flickered back to life along with the fuel pump priming,,,, but,,,, after charging up the battery, could not get the check engine light to come on again in the key on position.
Ok, so I'm using a known good relay but I'm spending $10 on a new one, at the same time I'm re-checking / cleaning the connectors to that relay and I'm going to check / clean the connector to the fuel pump.
quote
Originally posted by 85 SE VIN 9:
I think there was a guy who's OP sender fuel pump circuit burned his ECM. Don't remember who or the title of the thread, but it was a few years ago. If you suspect the FP relay, by all means replace the ten dollar part. Upgrading to the '88 OP sender seems like another no-brainer, but I still haven't done either of mine.
Dog gone it, that just happened to me on my 88 coupe 4 banger, OMG, talk about tunnel vision on fuel pump, now that really makes sense to me now that you mentioned it.
No check engine light or fuel pump prime on initial key on.
Installed new oil pressure sender, that checks out, new fuel pump relay too. I took a meter to the hot at ECM and that was 12.3 volts the battery was 12.35 volts. Double checked the fuses, ok there. I can turn the fuel pump on by applying 12 volts to the fuel pump at ADL.
It's late but tomorrow I will pull ECM and open it up, you know, just double check to see if it looks ok or if it's crispy critters.
I've owned this 86 Fiero for 16 years and this is the most confounding problem I have ever had.
At this point, i would take a wizz on a spark plug if I thought it would help.
Battery voltage should be much higher, more like thirteen. Maybe you have a drain or short somewhere. If you disconnect the battery do you get a spark between the cable and post?
Originally posted by 85 SE VIN 9: Battery voltage should be much higher, more like thirteen. Maybe you have a drain or short somewhere. If you disconnect the battery do you get a spark between the cable and post?
That voltage should be good with the engine off. I've never measured 13 volts under battery power alone while performing checks.
quote
Originally posted by jetman: Back to square one.
No check engine light or fuel pump prime on initial key on.
Installed new oil pressure sender, that checks out, new fuel pump relay too. I took a meter to the hot at ECM and that was 12.3 volts the battery was 12.35 volts. Double checked the fuses, ok there. I can turn the fuel pump on by applying 12 volts to the fuel pump at ADL.
It's late but tomorrow I will pull ECM and open it up, you know, just double check to see if it looks ok or if it's crispy critters.
I've owned this 86 Fiero for 16 years and this is the most confounding problem I have ever had.
At this point, i would take a wizz on a spark plug if I thought it would help.
Suggestions? Anyone?
If you're sure the PROMM is not damaged you have a wiring problem somewhere. Check your grounds extra carefully. You can get a good reading on the voltmeter with a weak connection that will not cut it under system power.
If you have no luck there, bypass the harness power supply with direct positive and negative feed to the ECM. If it works that way suspect a break in one of the appropriate harness wires and possibly an issue with the ignition switch wiring.
Take the plastic secondary pin retention clips out of the ecm connectors. WITH THE ECM STILL CONNECTED , key on AND THE PROBLEM HAPPENING back probe the three power wires, switched and unswitched. Fix the problem with the one that is low voltage. My guess it is the orange ones.
[This message has been edited by phonedawgz (edited 08-13-2015).]
Take the plastic secondary pin retention clips out of the ecm connectors. WITH THE ECM STILL CONNECTED , key on AND THE PROBLEM HAPPENING back probe the three power wires, switched and unswitched. Fix the problem with the one that is low voltage. My guess it is the orange ones.
I saw 3 orange redish wires, basicly one on each end and a middle one.
Key off the end wires had 12.2 volts each, middle none.
Key on the end wires had 4.6 volts and the middle 2.3
Disconnected from the ECM the end wires had 12.2 volts each, middle none with either key on or off.
I pulled the ECM out, opened it up, no major burns to see but a faint burnt smell, i think it's a fry baby.
If with the ECM hooked up, using backprobing, B1 and C16 do not have +12v or there about, the problem IS in the wiring to the ECM.
Put your meter on C16 or B1, have someone look at the voltage and wiggle around the ECM reset connector. If that doesn't make the voltage jump up and down check the wiring at the power distribution post. If that isn't it then flex the fusible link.
IF YOU ARE READING LOW VOLTAGE AT THOSE TERMINALS WITH THE ECM CONNECTED, THAT IS INDICATING YOUR PROBLEM, AND THE ECM ISN'T BAD.
Sorry I haven't updated, busy with projects but,,,,,,,,,,,
I checked the power to the ECM connectors, we look good. Double checked grounds and connectors in engine bay, and installed a new ECM
I actually got the engine to start and run for about 3 seconds and I was able to repeat that several times.
I don't have a check engine light and my fuel pump won't turn on at the key on position. I swapped out fuel pump relays, checked fuses and I am only able to get the fuel pump to run by hot jumping 12-volts to the ADL connector.
I'm going to bring home from work a scanner and double check the check engine light.
I'm off to the forum archives but if anyone knows something, please chime in, thanks!!!
I've now got a check engine light and fuel pump prime at initial key on. But it won't fire at all.
It's somewhere in the wiring between coil and distrubutor.
MSD ignition system hooked up, I have check engine light and fuel pump prime but no fire.
Stock configuration, (no msd system) I have no engine light and no fuel pump prime but it'll fire for about 2 seconds.
I'm posting this so anyone else out there will have answers, you know, after it hits the archives.
Man alive, but I'll get to the bottom yet!!!
Probe the power wires to the ignition coil and the distributor and make sure you have 12 volt power while cranking the engine. If you have power going into the distributor and nothing coming out that's likely the trouble spot.
I suspect a MSD ignition box system that may have gone bad, removed it, but i was also checking out connections again, ECM is up, check engine light on.
Long short, fuel pump is going out, won't always prime up in the key on position so I decided to let her go, the 86 silver bullet has found a new owner and hopefully will be back out on the road again.
Oh yeah, the ol girl decided to pout at me, turn signal lights acting up as I was showing her to the new owner.
So good by to my first love, my 86 Fiero, be good to your new owner.
