Dieseling 427

[Cracker]

Eljaro,

What red charging light on your contemporary are you referring to as my car does not have one - I think. My dash has a green light by the ignition, a blue light for high beams and a green light that is always on near the Tach. Where is the red one? What amp diode did you end up using and off of which wire did you splice it in off the regulator. I'm finally tired of diesling upon shut down.

BTW, thanks for the info regarding AMP, I bought there lower control arms for my car and plan on install/swap over the weekend!

[Eljaro]

Well Tony,
it wasn´t the diode after all. Somehow after wiring the diode between terminal marked I (the others are A,S and F) on the regulator and the read light which is allways on when the ignition key is on (remeber, it's a Contemporary, and has this red light which is always on with the ignition and a blue one for the lights) the dieseling did not happen after three trials. Next day it was all the old story again.
I noticed that the valve covers and heads would get very very hot in just 5 minutes with the engine just idling.
A very hot compression chamber can cause dieseling.
Since the dieseling did not happen before the last rebuild, which only included a sharper cam (282S comp solid cam), I recalled what else I did change. One thing was the addition of an oil restrictor in the oiling hole to the rocker shafts. The restrictor may improve oiling to the crankshaft, but that is only an issue with a regular pumps. A high volume pump will probably not need a restrictor to supply suficient oil to the crankshaft. What the restrictor does is to allow less oil to the valvetrain, and so prevents it from getting enough cooling through the oil.
I removed the restrictors and the engine does not get as hot as before, even after 10 minutes running I can still touch the valve covers with my bare hands.
I will keep the restictors removed for now, since the oil pressure did now decrease.
But, dieseling still happens.
I am now having a close look at my carburetor, because the throtle blades do not shut completely, and I always see gasoline around the accel.pump injector and on the blades in the primary bodies when I shut the engine off.
I think this is not normal and believe that is has something to do with the dieseling.
Does this happen with your carburetor? Mine is a 850CFM all mechanical 4 barrel Holley. I would very much like to know if that wet aspect of the carb is happening to anybody else.
I'll keep a post on this as soon as I make progress on this nasty dieseling.
Any suggestions welcome
Stefan Pietzsch

[decooney]

Eljaro,

In addition to the items formerly mentioned... try these and see what changes, if anything. Not all permanent fixes, but I noticed some changes after a few of these tests.

1) After a drive, idle your car for 20 seconds solid and shut it off. See if it diesels as bad or if it improves.

2) Retard initial timing to 10 degrees, and see if it still occurs. I'm not suggesting you leave it this way, but its a test to try.

3) With MSD, gap ALL spark plugs to .045 and try again. See manual for your MSD. It says to gap them more...

4) Check for vacuum leaks and seal them, retorque intake bolts,etc. See if it still occurs.

5) Check your vacuum with a gauge. Compare that to what power valve(s) you may have in your carb - just for grins.


Good Luck. Curious to see what you find out if you try these.
Duane

[NROTOXIN]

Back off the throttle screw all the way while the car is running keeping the idle at 900 rpm with your hand, turn off the ignition switch and let go of the throttle at the same time......if it works you are a fine candidate for a SOLENOID
Mine works fine at 1K (no air no run on)
curtis

[GEORGE ANDERSON]

I agree with the Idle...get it down...

[Cracker]

Clois,

Thanks for the advice regarding the Fan Switch. In my case it has drastically reduced the "run-on event" when I turn off the fans before I turn off the motor. Thanks again.

[Eljaro]

Well, it looks like the dieseling problem on my 427 C/O is solved.
I rechecked the timing mark on my pulley and damper and found it to be ok!

Just to inform you, when I put the engine together I found that it had either a wrong timing mark pointer or that it had been installed backwards.
I found the correct TDC and bent the marker so as to show 0º TDC.

I am using a super-duper dial-in advance electronic timing light and thought that the timing was spot on.
Well no, it wasn't.
I had set the advance with the electronic timing light at 14º, so that I could have the butterflys pretty closed but still get a decent idle. Dieseling still ocurred.
I took a 30 year old RAC induction timing light I had laying around in the junk box and hooked it up between spark plug #1 and the plug wire .
Since mine is an MSD 6AL ignition, the multiple sparks it produces generate multiple flashes which are not easy to distinguish with an old induction timing light. But looking at the very first flash mark I could see the timing was actually 0º, so no advance at all.

I adjusted the timing to the correct 12º advance with the RAC light and in order to get an idle of 700rpm I had to back off the idle screw almost one full turn.
The butterflys are now almost closed, (idle screw is now just 3/4 turns in),
the idle is now really nice and smooth (even at 700rpm !) and during the two dozen times I switched off the engine no dieseling ocurred
Resumee:

1.Some electronic dial-in timing lights are no good with MSD multiple spark electronic ignition.

2. The timing mark on your pulley or timing pointer may be wrong, and your timing may be way off.

I hope this gives all the Dieseling sufferers some extra comfort and hopefully also a definitive fix.