A Diesel Big Block

[Gary C.]

My 67 427/435 sometimes continues to run on (diesiling - much like the 73 to 78 or so smog equipped engines would frequently do) after turning off the ignition switch. It seems to do this if I cut it off prior to reaching operating temperature. It usually shuts down fine when it has reached operating tempature. Can someone expain how this occurs and any fix. I could not find anything in the service manuals re this condition.

Thanks in advance.

[Joe L.]

Re: A Diesel Big Block

Gary-----

With the engine below operating temperature, the automatic choke will likely still be on and the fast idle cam on one of its "steps". This causes a somewhat increased idle speed. It may not be very much higher than normal idle speed, but it's, at least, a little higher than normal idle speed. With a high compression big block, if not many other engines, too, that's often all it takes to cause run-on after ignition cut-off.

[John H.]

Re: A Diesel Big Block

Gary -

May be related to the choke not being fully open and it's possibly still on the first step of the fast idle cam, holding the throttle plate open beyond idle position so the transfer slot is exposed; this shouldn't occur, however, if your choke pull-off diaphragm is functioning.

[Gary C.]

Re: A Diesel Big Block

Thanks Joe and John

I was confident you both would have some insight. I too though it might be choke related as it does not do this when the choke is competely off.