I have spent the last 2 months working on a number of items that were due..as I near 100k miles on my 93. I had the car running great for 2 weeks, starting up with no issues, running as well as it has in years. I have not had it out as the weather in Pittsburgh is not very welcoming but I was ready to take it out a few days ago when we got better weather, and of course...no luck.

Prior to the last 2 months of work I have had an inermitend no start for 2 years. Last year I replaced the starter and battery...and it was much better...and less frequent. typically it would not start after it was running a while, and opening the hood and tapping on the ECM would get it back up and running in a minute or so. I have had a battery drain for the last 2 years as well.

Over the last few weeks I have started it every few days, let it run for 15 or so minutes. Last time it started last week it ran for about 15 seconds...then died. I was out of the car moving things around...it certainly caught me off guard. After that, it has not started.

Here is all I did to the car the last 2 months before this no start:

Waterpump, Opti, Plugs, Wires, Thermostat, Fuel Injectors, Alternator, Belt, Coolant and Oil Change. Once all of those were done it ran immediately, no issues at all for 2 weeks.

Since the no start last week:

Pulled the codes...there were a lot in history H31, H33, H35, H37 (all related to new head unit and amp I believe that I just installed - all cleared out and not coming back).

H41, H54, H72, H74 in module 1.
H41 and H64 in module 4.
H72 in module 9.

I went through and cleared the codes. The only one I get now is H41. After I clear it , it's there again the very next time I try to start the car.

Since the battery was dying anyway and under warranty I went in and replaced it today, cleaned the contacts and installed brand new bolts. I also checked the fuse block behind the battery and pulled all fuses, cleaned up the contacts as they were dirty and put them back in. I checked fuel pressure, right at 40 when I turn the key and usually stays there after I turn the car off. Every now and then it drops ommedially, but 4 out 5 times it stays at 40 and does so for at least an hour if not more. I replaced the fuel filter and fuel pump about 5 years ago...and I hear the pump run for 2 seconds as it should.

I'm trying to figure out next steps.

I have fuel pressure regulator that I am ready to install, regardless of this has any thing to do with the issue since it's probably over due. I changed out the fuel pump relay under the passenger side dash in case it was not operating properly, even though the pump does come on for 2 seconds, I though maybe it was running after that? hence the car dying? I also have a new fuel filter to put in, thinking possibly its getting to 40 pressure, but not getting enough flow still? I have done some research on the ICM and in watching some videos and looking at wiring diagrams and wondering if that or the coil could be the issue...but here is where I am stumped - the four wires I have going in to my ICM from left to right are what i believe to be pink/orange, then yellow then black the white. I think these are the colors, they are so faded it's hard to tell...but then I see wiring diagrams menioning purple, then I see vides showing green? I want to test these with a light tester but don't know which are which.

I don't mind replacing what I have done as I feel the car is overdue...but i don't want to start replacing questionable items like the coil, ICM, ECM if they are not bad. The water pump and Option was done because the water pump was leaking, that led me thing care of other items while I was doing that work.

Any thoughts on my wiring question, testing the ICM and Coil...and anything else I may not have thought of?

2 last items to note, I tried using a scanner to pull the codes...and even though it says for OBD1 and it also shows a 93 vette in the menu, it is not making a connection. I can hear the diagnostics running, and it is blinking code 12 but it kind of stops, then restarts...and after about a minute says it can not make connection. not sure if that is relevant. of course I just pulled the codes with a paperclip. #2 I found blue grommet under the car in the coolant pan when cleaning it out, would have come from a harness...but I checked all the ones I remember disconnnecting while doing all of this work...cant find one missing? still that would just keep moisture from going in...should not have anything to do with my no start...and it would have been missing the whole times its been running anyway.

 

Ready to get the weekend started and hoping to test out the wiring, so I could use some help determining why my wires don't match other posts and info I have found. any thoughts so I can test the ICM and coil?

I will replace the fuel pressure regulator and fuel pump in the morning in hopes that it takes care of my no start, or crosses 2 items off the list and takes care of some good maintenance.

 

Random and/or strange electrical issues on 1992/93 Vettes can often be a problem with cold solder joints in the ECM. SIA Electronics did a great job rebuilding the ECM in my 92 and it has been good for years now. I had all kinds of random errors, A/C would stop working and all kinds of electrical demons before that.

 

I appreciate the thoughts...I did the last bit of checking I could think of, pulse at injectors power to the icm and coil. while testing the icm I found that it is not switching on ...it has power, but when you start the car the white wire is not blinking on the tester. based on what I have found in posts and online, that also points to the PCM/ECM.

I did replace the fuel filter and fuel pressure regulator...so I know all of that is good. fuel pressure is fine and holding.

I have pulled the ECM and am sending to SIA tomorrow.

 

ECM received back today, refurbished. reflowed due to cold soler joints

plug in, no dice...it won't turn over. I hear the fuel pump coming on most of the time when I turn the key before starting, but there are times I don't hear it and just hear a click up near the battery...maybe 2 out of 10 times I don't hear the the fuel pump come on. When I try to start it crancks but won't turn over. when I check codes, I get H41 in module 4. If I clear it out and just tun the key to on position, no code, but as soon as I try to start, I get the code back.

outside of shipping back to SIA again, any other thoughts?

 

IAC valve. I have had a few cause a no start when that fails. They're cheap, grab a new one from Summit Racing, i have used Standard Motor Products brand the last 4 i did and i haven't had an issue with those, quality appears to be as good or better than AC Delco. Grab new gaskets for the throttle body while you're at it, you may struggle to remover the IAC without unbolting the throttle body, and you really should give the IAC path a good clean while you're at it.

You will not hear fuel pump go on every cycle of the key, if you turn it on after a delay you will hear it, but if you switch off and straight back on you may not, because it may not run every time. Don't be concerned about that.

Engine cranking is engine turning over, the starter motor is rotating the engine, or turning it over. This is good.

If the injectors are getting signal, the distributor is somewhat functional.

I will go and check my book to see what DTC41 is.

I checked, it is cylinder select error.

Check that memcal is in correctly, and that it isn't damaged.

Show a photo of it if you can.

 

Thanks for the feedback, but not sure that is the right code description for a 93? regarding the memcal if I open the ECM then I void the warranty on the EMC I just paid $250 to refurbish. I called SIA, they said to send it back and they can open it back up again and check it out again...so not sure I want to open myself and have an issue with that?

 

it is, it came from my 93 Service manual

 

thanks for the confirmation!

 

Sorry to revive this zombie but did you ever resolve your issue?