When I had my 383 carb'd and I started it for the first time, it dieseled when I turned the key off (kept running for about 5 seconds). Well now that I've got the Megasquirt installed running my HSR, I seem to have that problem now. I'm still trying to figure out how to get the timing just right so I Can at least get it up to operating temp to tweak the base timing, but I didn't think it was possible for a fuel injected motor to diesel like that? I figured once the injectors stop firing, even if the dizzy was 40 degrees advanced or so, how could it still fire off?

 

no one?

 

you could try a colder plug or less timing. carbon build up also causes this. could this be a tuning issue?

 

but even if it's a timing issue (which I know it is), if the injectors aren't firing, how is the motor even able to diesel? Carb'd motor I could see because as long as the the motor is pulling in air, it will pull in fuel as well. But with injectors not squirting, and the motor not even up to operating temp, how is this possible?

 

only one reason for dieseling on fuel injected motor..... leaking injectors

 

maybe you are just running so rich at idle there is plenty of fuel to keep "running on." ya gotta have too much advance, either way, and some glowing carbon in the exhaust port might be making it worse.
if it had a carb i would set the timing to 41.5 degrees at full advance conditions (probably 3500 rpm or so) and see what it's like at idle. not sure how that philosophy works with efi, but it could put the advance back enough at idle to stop the dieseling.

 

do you have your cooling fans hooked up to a power source that comes from the ignition switch?

 

I think I figured out the problem; way too much timing and running pig rich. I reset the dizzy to TDC and tried to fire her off, she fired off once, ran for 1 second, then died. I pulled the injector fuses and cranked it over for about 5 seconds. All the while my AFR gauge was reading lean, then it fired off again for about 1 second, then shut off. SO know I know I am WAY rich, so I'm in the process of learning how to lean up the AFR during cranking, or even at idle, using MegaTune. I'm trying to find a base MSQ that I can use as a starting point, even the original MSQ that was based off a 350 TPI doesn't seem to work.

DENN: My cooling fans are hooked up to a thermal switch on the block thats hooked up to a 12V in run, why do you ask?

 

i've never seen a cold motor diesel, only a hot motor.
the reason i was wondering is because i've seen people hook up the power side of the fans to a switched power source from the ignition switch that supplies power to the ECM and ignition system. with the fan ground side wired to ground, the fans run any time the key is on.
when the key is turned off, the fans supply power for a few seconds and although poorly, the motor will continue to run for a short while. some people mistake that for dieseling.

sorry i couldn't be of more help.

 

While doing some TBI reading, I ran across this TBI diesel possibility, thought I would add it to this thread.

If the canister purge valve is allowing fuel vapors to leak into the intake manifold as the engine is being shut down it will supply the fuel necessary to cause the engine to diesel. To check crimp or block off the canister purge hose, than run and shut down the engine several times to check for any dieseling. If the dieseling is gone, replace the canister purge valve.

Jim

 

thx for the info. I got rid of my evap, emissions and A/C long ago. So for me, that's not the case. Good info though