92 Cutlass Supreme 3.1 no injector pulse signal

[tedciotti]

New: 2 different ECM Prom correctly swapped, CSP sensor, ICM, Fuel pump

 

Great fuel pressure, Wire to wire all check ok, Car runs on starter fluid

 

No injector pulse, tested per "1992 Engine Performance Basic Diagnostic Procedures GM 1-31 | No Start - Engine Cranks Okay - Ignition System W Body"

 

Stuck at step #8: I unplugged the blue wire, that comes out of the ECM, from the injector connector. From there, I attached test light to the blue wire on one end and the other to the + battery. No flash at all while cranking engine. Per 1992 Engine Performance Basic Diagnostic Procedures GM 1-31 - says bad ECM. Tired another ECM, still no flash. Could there be another sensor or input the is bad and causing a cascade affect resulting in no pulse?

[jeffreyeffrey]

Having this exact same problem with a TGP. Did you ever resolve this issue?

[Galaxie500XL]

Any codes being stored by the ECM? First thought would be no crank position sensor signal...but that would only be a guess based on the available information.

[RobertISaar]

crank sensor must be active if it's sparking(with the ICM in module mode).... whether or not that signal is making to the ECM is a good thing to look into.

 

a 92 3.1 doesn't have that type of code though. would need to look at the datastream to see if RPM is being registered.

[Galaxie500XL]

I was probably thinking of my troubleshooting steps with the LQ1 a few weeks ago with my bad crank sensor...if the correct number of crank pulses weren't counted each revolution, the ignition control module sent no reference pulse to the ECM...but I'll freely admit I don't know if that also holds true for the 3.1.

crank sensor must be active if it's sparking(with the ICM in module mode).... whether or not that signal is making to the ECM is a good thing to look into.

 

a 92 3.1 doesn't have that type of code though. would need to look at the datastream to see if RPM is being registered.

[RobertISaar]

all classic 60V6 engines use the same ICM. with the 3.1, there is no cam sensor or 24X sensor(unless you have the really oddball 93 only california emissions 3.1 SFI, which uses a variant of the 93 3100 PCM).

 

if you have those signals available, you can do some error testing based on those signals. but the 7X crank sensor(which the ICM creates the 3X reference pulses from) is an absolute necessity at all times. any kind of intermittent or lack of signal from that will cause a stumble/stall/no-start.

 

luckily, the ICM has it's backup mode, only runs on 10* of advance, but it will function without an ECM to control it.

[Crazy K]

To check a crank sensor, you should be able to use a blade type bulb in the end of the yellow purple wire from the CPS that terminates at the coils. hmm...

 

Other things that have caused no start on such engines include a bad fuel injector that shorts out the complete injection circuit. you would need to pop the plenum off and check each injector with a multimeter.

[jman093]

I'm with Ken. If you are correct about it running on spray, correct about fuel pressure being 43 psi, and correct that there is no injector pulse, a shorted injector is about your only culprit.

[jeffreyeffrey]

Wow great response. Okay so if one injector is out, it takes all of them out? I had a'91 3.4 cutlass 15 years ago and I remember that was the deal on that. Same on a TGP? A little quick history... The last time it ran was Thursday, and I shut it off with the key. There's spark. (pulled one plug and turned it over) There's enough pressure on the rail that it soaked the hood insulation when I pressed the Shrader valve. No Noid light on injector. I tried an ECM off a '90 3.1 supreme, nothing. I'm going to find a new ICM tomorrow. There was a code 42 before so I'm hoping that's it. I read somewhere that ICM dictates to the ECM when to fire the injectors.?. Is that correct. I figure the Crank sensor must be okay since I have spark.?. If ICM doesn't work I'll start thinking wiring.. Am I on the right track here?

[White93z34]

If the ICM does not fix it, i'd look to injectors. I've had and seen on other cars a single bad injector take out the other 5.

[jeffreyeffrey]

Resolved!! Put in an ICM from a 2005 Alero. (Yes same part number AC: D1998A) And it runs.

 

What did I learn?; ICM does indeed govern the fuel injectors. Or at least the fuel injectors rely on the ICM. Would have never guessed that. I assumed the ECM was taking info from the CPS and timing both FI and ICM...

 

I ran the TGP about 20 minutes afterwards and got no codes. So in this case Code 42 was a failing ICM.

 

Thank you everyone for your input.

[RobertISaar]

the ICM creates the 3X reference signal from the 7X crank sensor's signal. the 3X reference signal is fed to the ECM for it's use as both crank speed and positioning. with no 3X signal, the ECM would never know that the engine is spinning. the ICM would still know that it is spinning and fire the spark plugs in backup mode though.