quit running

[Edward J.]

Re: quit running

Will, I don't think I would be looking at the body module, the only area in the BCM that is going to keep the car from running is the pass key operation, and if its not reading the key, the fuel pump is disabled.since there is fuel - strike that.

The next step is the fuel pressure- the LT-1 engine im going to think about 40-45 psi .( no manuel)

And did you happen to check for spark at the plugs? or coil?

I JUST HAPPEN TO THINK YOUR 91 IS NOT THE LT1.BUT PRESSURE SHOULD BE ABOUT THE SAME- KEY ON ENGINE OFF 40-45

[Wilbur M.]

Re: quit running

goining thru the owners manual i came across an item that says when you turn on the ignition the battery light should come on and then go out as a check.my battery light stays on.the battery is good.i disconected the alternator and the light went out.i thought maybe a bad diode was the problem.

[Edward J.]

Re: quit running

Not related to a no start unless you battery is dead.

[Paul J.]

Re: quit running

Wil,

I don't understand what the connection between gauges, dash indicators, and the ECM is, but I've seen indicators give strange readings when the ECM is bad. The ECM does not control those circuits, but there is something in the circuitry that connects them. I've run into this on different makes of cars. The week before last I was working on a friend's 08 Mustang that had dash indicators coming on and would eventually die and not start. This would happen intermittantly. The dealer had him replace the battery three times, which would solve the problem each time. The fourth time he brought it to me. I spent some time with it and everything looked good, but the dash indicators were the key. It looked like the ECM to me, so I had him go to a different dealer, as I quit messing with ECM's a long time ago. The dealer confirmed my diagnosis and has ordered a new ECM. We'll see if it works.

My mother's 04 Buick had similar symptoms several years ago (dash indicators and would'nt start). She was far away from my shop, but she also had an extended warranty, so I put it on the flatbed and had them haul it to the Buick dealer down the road. They replaced the ECM and it has been fine since.

Paul

[Wilbur M.]

Re: quit running

i have been working on this for the past week and to no avail.i bought a new ecm and installed it this morning.still no start and no radio and dash readouts.i connected my tech 1 and got the message diag circuit check failed.i put the original ecm back and the tech 1 gave me the code 12 that means it is ok.which one do i beleive.im at wits end with this. i also did a starter draw test and battery load test.both are ok.

[Paul J.]

Re: quit running

i have been working on this for the past week and to no avail.i bought a new ecm and installed it this morning.still no start and no radio and dash readouts.i connected my tech 1 and got the message diag circuit check failed.i put the original ecm back and the tech 1 gave me the code 12 that means it is ok.which one do i beleive.im at wits end with this. i also did a starter draw test and battery load test.both are ok.

Wil, sorry you're having so much trouble. Does'nt working on modern car electronics S***?

Did the new ECM come already flashed? Also, you can get the old one re-flashed, which may or may not help. Somewhere back in this thread I remember mention of a security chip in your key. If your car has this then there may be security codes that must be removed and resinstalled with the reprogramming. That would affect the new ECM even if it came flashed, as it may not be recognizing the chip and won't allow the car to start. It is my understanding that a GM Tech II scan tool (or equivalent) is required, but as I said earlier, I stopped working on ECMs a long time ago. The codes are available from GM.

You can get your ECM flashed by specialty electronics companies, any knowledgable garage, or the dealer (sic).

I was looking for my tech info but I can't find it, so here is a excerpt from the "ECM-ToGo" web site:

"Often when your computer is failing there is misdiagnosis and people will spend hundreds I've even seen customers who have unfortunately paid over a $1000 on their car on repairs and part replacement before he finally got to us and he found out he needed only an ECM to solve his problem. I have seen people go without their vehicles for months because the mechanic could not find out he had a computer failure. On the other hand their have been countless others who have paid this amount and more on new computer ECU(s) and the problem does not go away! The key is proper diagnosis! My father always said measure twice cut once. So we are firm believers in getting a second opinion or third if necessary to collaborate repair diagnosis that can be financially crippling.
Most common misdiagnosed parts are battery, distributor, ISC motor, TPS switch, injectors & intake cam sensor, and other sensors or bus system including but not limited to the harnesses. If the technician does not figure it is the ECM they may sell you parts you may not need."

Sounds a little like your adventures, doesn't it. I think that you may have a security issue (key chip). I would also look into making sure the ECM was/is properly flashed.

Paul

[Ken A.]

Re: quit running

Wil, sorry you're having so much trouble. Does'nt working on modern car electronics S***?

Did the new ECM come already flashed? Also, you can get the old one re-flashed, which may or may not help. Somewhere back in this thread I remember mention of a security chip in your key. If your car has this then there may be security codes that must be removed and resinstalled with the reprogramming. That would affect the new ECM even if it came flashed, as it may not be recognizing the chip and won't allow the car to start. It is my understanding that a GM Tech II scan tool (or equivalent) is required, but as I said earlier, I stopped working on ECMs a long time ago. The codes are available from GM.

You can get your ECM flashed by specialty electronics companies, any knowledgable garage, or the dealer (sic).

I was looking for my tech info but I can't find it, so here is a excerpt from the "ECM-ToGo" web site:

"Often when your computer is failing there is misdiagnosis and people will spend hundreds I've even seen customers who have unfortunately paid over a $1000 on their car on repairs and part replacement before he finally got to us and he found out he needed only an ECM to solve his problem. I have seen people go without their vehicles for months because the mechanic could not find out he had a computer failure. On the other hand their have been countless others who have paid this amount and more on new computer ECU(s) and the problem does not go away! The key is proper diagnosis! My father always said measure twice cut once. So we are firm believers in getting a second opinion or third if necessary to collaborate repair diagnosis that can be financially crippling.
Most common misdiagnosed parts are battery, distributor, ISC motor, TPS switch, injectors & intake cam sensor, and other sensors or bus system including but not limited to the harnesses. If the technician does not figure it is the ECM they may sell you parts you may not need."

Sounds a little like your adventures, doesn't it. I think that you may have a security issue (key chip). I would also look into making sure the ECM was/is properly flashed.

Paul

More BAD advice. A 91 is controlled by an eprom, which in this case, sounds like it may be the culprit. Borrow a known good eprom/memcal and install in your ECM. By the way, you could have a bad new ECM. Who rebuilt it? If not Delphi, cross your fingers. There is NO post install flashing until 1996 or OBDII

[Paul J.]

Re: quit running

More BAD advice. A 91 is controlled by an eprom, which in this case, sounds like it may be the culprit. Borrow a known good eprom/memcal and install in your ECM. By the way, you could have a bad new ECM. Who rebuilt it? If not Delphi, cross your fingers. There is NO post install flashing until 1996 or OBDII

Wil,

Take the chip out of your new ECM and put it into your old one, then reinstall your old one. When you do this, look carefully at the chip. See if the surface is smooth. If there is a variance such as a wave, risen area, bubble, hole or crack, that chip is bad and the ECM probably is too. The capacitors used in earlier ECMs caused problems over time.

Sorry that I missed that your car was pre 1996, I lost track of the post over the last few days.

Hopefully, your new ECM is from a reputable supplier. Delphi is not the only one...talk about BAD advice!

Paul

[William C.]

Re: quit running

Radio and dash feeds require electricity and it is the same electricity that makes the engine ren. Good advice in this thread, if you can hear the fuel pump when you turn the key on, turn the key off anf unscrew the cap on the fuel rail (pass side) there is a schrader valve under the cap, depress the valve and if you have pressure (should hold for a few minutes) it should shoot gas 6-10 inches high out of the valve. If it does, then look for spark, a timing light while cranking the engine will fill the bill for that check. If no spark, look for the problem, no power to the distributor or ??? If ok, check for signal to the injectors, you can purchase an inexpensive set of "noid" lights on the flea and pull one of the connectors off your injector set (any one) insert the noid module and crank the engine noid light should flash. If good, then move to the injectors themselves and check for a shorted injector. The injectors fire in a parallel system, so one shorted injector will kill all fuel to the engine. If no shorted injectors are found (resistance should be 12-14 ohms per injector approx) then the last check is to apply 12 volts across the terminals of each individual injector in turn. You should hear a difinative "click" when power is applied to each injector. It is very unlikely that you will get to this point, but at that juncture you have essentially verified the electronic fuel management system. All this assumes you get a 12 code (and no other) when you put the computer in diagnostic mode.

[Clem Z.]

Re: quit running

Radio and dash feeds require electricity and it is the same electricity that makes the engine ren. Good advice in this thread, if you can hear the fuel pump when you turn the key on, turn the key off anf unscrew the cap on the fuel rail (pass side) there is a schrader valve under the cap, depress the valve and if you have pressure (should hold for a few minutes) it should shoot gas 6-10 inches high out of the valve. If it does, then look for spark, a timing light while cranking the engine will fill the bill for that check. If no spark, look for the problem, no power to the distributor or ??? If ok, check for signal to the injectors, you can purchase an inexpensive set of "noid" lights on the flea and pull one of the connectors off your injector set (any one) insert the noid module and crank the engine noid light should flash. If good, then move to the injectors themselves and check for a shorted injector. The injectors fire in a parallel system, so one shorted injector will kill all fuel to the engine. If no shorted injectors are found (resistance should be 12-14 ohms per injector approx) then the last check is to apply 12 volts across the terminals of each individual injector in turn. You should hear a difinative "click" when power is applied to each injector. It is very unlikely that you will get to this point, but at that juncture you have essentially verified the electronic fuel management system. All this assumes you get a 12 code (and no other) when you put the computer in diagnostic mode.

remember the older GM injectors are fuel cooled and the coil insulation is not ethanol safe.

[Ken A.]

Re: quit running

i have a 1991corvette convertable.i had it since new.it has 18000 miles.it ia garage kept and has never been in any weather.i got it out this weekend to get ready for summer.i went for a ride and it stopped running.as this happened the radio quit and the display on the dash stopped working.i replaced the fuel pump,relay.coil,and pickup module.everything else seems to work.i hooked up a teck 1 and it showed no codes.can anyone help me with this problem? will miller

Check for leakage from the water pump. The optispark unit is right below the water pump and seepage(unseen) easily ruins your opti unit and will corrode the coil wire, as well, causing all kind of misfires. You may have spark, but it may fire at the wrong time. If your engine cranks and the fuel pump comes on, then the BCM is functioning correctly-as far as the start system goes. Also try the battery disconnect for 60 seconds. It will "reboot" the computers. The radio/dash problem maybe a side issue; check for a blown fuse, especially the ones marked cluster. See my earlier post re: ECM. You are still getting incorrect advice on this issue. You cannot examine the "eprom" as it is mounted in a special T shaped carrier. Delphi is the only reman center that has the software to test GM ECM's, as they (Delphi) built them and consider the software their property. I sorry if this statement offends some of you, but it is a fact-not speculation. If your distributor is bad, remember the cheap Chinese distributors were running an 80% failure rate and will cause you to throw tons of money at the wrong things. One other suggestion: is your battery over 3 years old? A weak battery will cause all of the symptoms you have described-the charge system MUST put out 13.8 volts to properly run the car.

[Clem Z.]

Re: quit running

remember the older GM injectors are fuel cooled and the coil insulation is not ethanol safe.

Many automotive professionals point to fuel quality as a primary suspect in premature injector failure. John McGinity at the GM Training Center in Golden Valley spoke frankly about this issue. He blames excess alcohol (isopropyl or ethanol) and fuel additives for many injector problems, particularly with the early GM Multec injectors. McGinity described how alcohol can permeate the bobbin for the winding on the injector coil, leading to shorted windings, lower resistance and eventual fuel delivery problems

[Joe E.]

Re: quit running

I had the same problem with a 94 and I had changed several components in the ignation system and had changed the ECM also. I tried everything I could and then got help from a friend who owns a garage and it was the new ECM that was no good. This friend told me that these electronic parts have a very high percent of failure when new right from the parts store.