454 continues to run

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454 continues to run

Home > Discussion Forum > Mechanic's Corner - Engines

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All Messages in Thread	Author	Date
454 continues to run	Kirk	8-13-03
My 454 Carb. engine began to continue to run after turning off the ignition. What is the cause, and what is the cure?
Re: 454 continues to run	Nathane958	5-3-04
I have a 454 in an 84 winnebego chieftan thats dieseling upon shutoff. I have a shut-off sloenioid, but is vacum controlled, not electrically from the ignition.I just recently had my quadrajet rebuilt, the rebuilder had elimintated alot of vacum lines, one of them being the solenoid.....wasnt even in the vacum circuit.He used the throttle stop screw as the idle adjustment. The choke appears to be holding the butterflys open in the primarys about a 1/4" even when hot. when i take the choke out of the vacum circuit it shuts off fine cause the primary butterflys are allowed to close all the way. Is there an adjustment on the choke? I see an adjustment screw of some type on the choke assembly, but am recluctant to adjust.I think the rebuild is fine was done by a reputable rebuilder, but the installer obviously doesnt know shit or didnt spend the time to do it right, he has a line of more expensive coaches waiting to be fixed. I made the mistake of paying him befor I drove it..., and now im stuck in this position. Seriously frustrating considering all the work ive done to this thing myself to bring this motorhome back up to par. Ive tried putting the shut off soldnoid back into the vacum circuit strait off the carbeurator but obviously....... this does no good, the shut off valve opens and closes while dieseling. He eliminated what i remember as a white 6 way vacum valve of some sort coming out of the intake manifold, i believe the shutoff solenoid was connected to this. big trouble, vacum nightmare here. Plz help.
Re: 454 continues to run	Sam Watson	8-13-03
This is not good for the engine, causes piston and ring damage. Since an engine requires fuel and fire to run, then there is a secondary ignition source, usually incandescent carbon deposits, or the sharp edge of metal that is glowing red hot. The sudden onset of "engine run-on" is usually the result of a vacuum leak. The carb itself is equipped with an anti-dieseling solenoid whose armature extends when the ignition is turned on. The idle speed adjusting screw rests aginst this extended armature in normal operation to give you "curb idle". When the ignition is turned off, the armature retracts, allowing the throttle blades to close and restrict the air/fuel flow into the engine below a point where the engine can run. There is another throttle stop screw for the throttle blades, but that is set to prevent the blades from binding in the throttle bores when they are completely closed. Try this, locate the idle stop solenoid on the carb, it will have a single wire going to it. With the engine off and holding the throttle slightly open, turn the key on and off and observe the that the armature should extend when the key is on, with the key off, close the throttle, the throttle stop screw should easily push the armature back into the solenoid. If that checks out OK, start the engine and let it warm up enough to get the choke all the way open, let the engine drop to idle, disconnect the idle stop solenoid--there is a connector on the wire for just this purpose-- the armature should retract and the engine rpms drop to 400 or less. If not, then start checking for vacuum leaks, don't overlook the throttle shaft bores in the carb. If you don't know how to check for leakage, post that, and I'll give you an easy method.
Re: 454 continues to run	william phelps	8-21-03
Sam has it very well layed out for you Kirk. The only thing I would add is to make sure the choke butterfly on top of the carb, is opening all the way when the engine is hot. I have been working on quadrojets for over 30 years and a lazy choke has caused your symtoms more than any thing else. There is a step cam on the passenger side of the carb connected to the choke that can hold your throttle open if the choke is not opening all the way. The other thing you might try if your going looking for a vacuum leak is to use water in a spray bottle. Adust it to a stream and then begin spraying it around the base of the carb with the engine at idle. If you have an excessive vacuum leak the engine will run very rough if you find a leak with the water.
Re: 454 continues to run	T Thompson	3-3-04
I have a 1988 Winn. Super Chief and it just started "dieseling" yesterday like described in this post. I'll also check for a vacuum leak or lazy choke. Is a vacuum leak an expensive fix? I just replaced the master brake cylinder two weeks ago and that set me back $635.
Re: 454 continues to run	John Ogletree	8-14-03
Sam, please do post your info about checking vacuum. My 454 is on an '87 Holiday Rambler Imperial Class A. Will my carb. have the solenoid you mentioned?
Re: 454 continues to run	Sam Watson	8-14-03
John, it may or may not. Take a look at where the throttle linkage connects to the carb, if present, it will be towards the front of the carb. To make yourself a vacuum leak detector, buy abt 3 feet of 1/4" vacuum hose and 1 foot of 1/4" copper tubing. Connect the hose to the tubing, start and warm the engine up. Hold the end of the hose very close to the opening to an ear while you slowly move the tubing along the manifold, carb, hoses, etc. Keep the tubing pointed rearward while you do this, otherwise it'll pick up the noise of the air coming off the fan.
1994 dodge caravan	Lloyd vail	1-21-06
How do i fix automatic choke on a 1994 dodge caravan or adjust.
Re: 1994 dodge caravan	taffy	12-19-07
Heater in 1994 dodge caravan won't work. Blows out cold air only. What should I do???