Hey everyone,

I have an 82 CE with a new Dynamic ECM.  I recently had some shop work done where they replaced the oil pump, water pump,  rebuilt the distributor, and adjusted the timing.  I have verified that the throttle bodies are balanced.  Now, when cold the car starts right up and drives great.  However, once I turn the car off and go in a store or the like, when I come out and try, it won't start.  I took the cleaner off and you can see that the injectors are not firing.  After waiting a bit of time, typically 5-10 minutes, the car will start and let you drive for as long as you like, with the same issue once you turn it off.  New 85 vette fuel pump and I have confirmed pressure when you turn the key on for the 2-3 seconds, then it drops off.  Checked the fuses and they are good.

Any ideas on what to check next?

Thanks,

Dennis

Also, checked and replaced the fuses just in case.  No change.

Are you confirming fuel pressure at the time it will not start? If so, then you have a control issue with the infectors, meaning the ECM is not commanding them to fire. It's possible a temp sensor is malfunctioning, tach signal(engine rpm) loss when hot, oil pressure loss when hot, etc. I would suggest pulling any codes out of the ECM to see if something is triggering a code at the time it will not start. Once the key is turned of, codes will normally disappear. They need to be retrieved at the time of malfunction. It's also possible the ECM is at fault, "new" or not.

Joel Adams
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Adam,

Thanks for jumping in.  Here are the answers I can provide.

Are you confirming fuel pressure at the time it will not start?

I have a fuel pressure gauge between the throttle bodies.  When the key is turned to on, regardless of start or not, the gauge jumps up to 13psi and then slowly drops if you don't start cranking.  If you keep cranking it stays at 13psi. 

It's possible a temp sensor is malfunctioning

Old temp sensor was moved from old water pump to new one.  Temperature gauge in car while engine runs has consistent readings with the ones prior to the water pump replacement.

tach signal(engine rpm) loss when hot

Tach gauge shows activity upon cranking.

oil pressure loss when hot

Oil pressure gauge shows higher pressures after new oil pump installed.  Runs 50-60 cold and drops to 35-40 at idle when hot.  This is 10-15 higher than the previous pump.

I would suggest pulling any codes out of the ECM to see if something is triggering a code at the time it will not start. 

Computer is not showing any codes.  No check engine lights, nothing.  I hooked up my computer and put the EBL Whatsup App to log and tried starting.  The log file does not show anything different than when it starts.

ECM has been running great up to this point and shows no issues when I hookup the computer and log.  The Dynamic EBL II computer that is now in there is a tuners computer made for the 82 Vette and keeps logs much longer than the original ECM.  

I did replace the fuel pump to the 85 vette one a few weeks ago.  Also changed the timing and that was when everything went wonky.  Car wouldn't run and when it did tried to die every time you hit the gas.  Then the water pump went out, I got injured, and into the shop it went.  They also evaluated the fuel pump and did not find any issues.  The replace the water and oil pumps, put a new coil and ignition module into the distributor, and readjusted the timing.  I figure this problem has only surfaced after their work, was not there prior, so must be related to the repair work they did.

I also went back to fossil oil versus synthetic.  Several knowledgeable people I know suggested trying it to stop the slow oil drip I have been having.  Not sure if that has any affect on all this or not.

Thanks,

Dennis

Team,

Not sure if this is related but just found this broken wire behind the distributor at the firewall.  Not sure what it does so if anyone knows.. please speak up.

Thanks,

Dennis

I'm no expert, but would guess that wire may have been disturbed when the work around the distributor was done.  It looks rather toasted.  Repairing the wire, or better yet - replacing it, may solve part or all of the issues.

One other thought - it is possible that there is a heat soak issue happening since it started up and ran fine after sitting for a bit.  Had that happen with the carb on "The Toy" causing a vapor-lock.  Solved that by putting a sandwich of gaskets between the carb and the intake to insulate the carb from the heat of the intake manifold (before the carb would be too HOT to touch, after it was just warm to the touch).  Didn't have a hot/warm start issue after that. 

Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

Aren't those ignition modules problematic?  Maybe put the old one back in.  Might be a heat thing with it too.

Norsky,

Some good tips there.  Definitely need to repair the wire.  As for insulating the TBI's, not sure if that is possible but will look into it.

Thanks,

Dennis

F4Gary,

This is the first time I have replaced one.  Put in a Flamethrower model, said it was for the 82, maybe it was too much.  Unfortunately the shop that replaced it did not give me back the old one.  Off to the parts shop to get a basic GM model and see if it works better.

Thanks,

Dennis

Yep...I missed that in the original post. I agree with Gary on ign module. Once again, "NEW" don't mean diddly squat. Hot start issues like yours definitely point to an ign module failure. Only takes 10 minutes or so usually for them to cool down enough to fire up again. Sometimes they never fire again.....it's a crap shoot. Would also explain why the infectors are not firing. Stock, GM style modules are fine for 90% of the engines out there....no real need for anything more exotic. Be sure to use the insulating grease that comes with the new module. It acts as a heat sink to draw the heat from the module into the aluminuminum distributor housing...which makes the module less prone to heat failure. 

Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Wasn't suggesting that the TBs be insulated.  Just was an example of how the carb was getting heat soaked and that insulating it reduced/eliminated the heat soak problem.  Was suggesting to somehow insulate the electronic bits which might help.

Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

Gentleman,

Thank you all for the great assistance.  The issue is resolved.  The previous mechanic that put the ICM into the distributor did not put the screws back in.  It was moving around and messed up the ground/wiring harness.  We found some screws and repaired the wiring harness and all is good now.  I really appreciate all the assistance.

Thanks,

Dennis

Thanks,

We didn't need that solution this time but I am definitely going to see if there are areas where we can put in some heat reducing components.

👍   👏

Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!