I have a 68 camaro coupe with a stock 250 engine. I am having trouble with the car deiseling after I turn it of in Park. We tuned the car to specs. Runs fine, but still deisels at time. any ideas on what may be causing this?
I dont like using it too much because it can weaken the seals. And I wouldn't use it on my engine. But "Sea Foam" works really good for something like that. Dump it in the carp and rev the engine from the carb. And add the rest in your fuel tank.
A buddy of mine has this same problem on a high compression 350. No amount of reasonable tuning would get rid of it. What happens is when you shut the engine off, fuel can still be drawn into the engine and hot spots on the pistons or chambers ignite it. He used to shut it off in gear and that worked great. What we ended up doing was getting an AC kickup solenoid from a junkyard, making a bracket and mounting it so that when the ignition was on, the plunger would come out and act as the idle screw (the plunger is adjustable), then when the car was shut off, the plunger popped back into the solenoid, closing the throttle completely and killing any fuel going into the engine. It's still in use today and works every time (four and a half years ago).
I just read somewhere that a car with higher compression can do this just from running fuel with too low octane. It would be real easy to check, just use the 92 octane fuel next tankfull (if you can afford it now a-days!).
WHOA GUYS, Timing has absoultly nothing to do with a diesel condition, You turn the key off and take all the ignition spark away once you turn the key OFF. So how does timing cause it to diesel?
The problem you have is a build up of carbon on the cylinders, this glows red hot and ignites the fuel after shut down and the engine still runs. you have two soultions here. Remove the carbon, or the fuel.
yes maybe some engine cleaner might work for a short time but the carbon will return,
the obvuious remedy is to remove the fuel, It you floor the gas when you shut it off the engine will continue to run without a problem so what GM did to fix the problem they installed an idle solinoid at the carb linkage, You might be able to find a used set up at the wreckers for a 6 cyl.
What it does is that you turn the base idle so low that it will not run at idle at all, the idle solinoid is active when the car runs and holds the idle higher than base which keeps the car idle normal,after you turn the key off the solinoid deactivates, the throttle closes fully and no more fuel no more diesel, this should farly simple to hook up in your car to keep a stock appearance. Here in Canada the emmission standards were behind the California emmissions standards and we started to see the idle solinoid in the early 70's
I agree with Rob.Canada that it couldn't be timing. I also agree with everyone that it is probably carbon. But, it could also be a vacuum leak, which creates an excessively lean condition, especially after the engine is turned off and the butterflies are closed. I had a girlfriend that had a 79 Dodge Aspen with their goofy slant six engine that had a horrendous dieseling problem. It would continue to run for an hour after you shut it off if you didn't put it in gear. When trying to adjust the carburetor mixture, I noticed the carb seemed a little loose. Sure enough, the twobarrel carb was loose on the manifold. I replaced the carb to manifold gasket and tightened her up.....and no more dieseling. Just another thing I would check if i were you. Good luck....I know it's frustrating.
Dieseling sucks! Remember the basics. For an engine to run, it must have air, fuel, motion, and something to ignite the mixture. With the key off, ignition must come from a hot spot in the cylinder head -- carbon build-up, plugs too hot, etc. fuel and air are easy. If the throttle is opened to normal idle, it will pass air if the engine is turning, and therefore, fuel must be drawn from the carb. The idle solenoid will work, by removing the air and fuel, but it's a band-aid. Clean out the carbon. GM top engine cleaner may work, or just pull the head. Have you changed (or even looked at) the sparkplugs?
Severe, with HEI, you may need a colder plug. Assuming your engine is tight, the plug insulators should be white on the hot side, and light tan on the cold side. If they're white all over, go to a slightly colder plug.
I couldn't begin to guess on plug heat range. If the insulator is too white, go one range colder. Every plug manufacturers numbering system is different, and some increase as the plug gets hotter, some the other way around. Start with what you have. As an example, with AC, many chevy's use an R45S, an R44S would be one range colder. Champ's might be RJ12Y, RJ14Y would be one colder (unless I have it backwards) A colder plug has a "shorter" center insulator. If you compare 2 plugs with very different heat ranges, you can see the difference.
[This message has been edited by JimM (edited 04-11-2000).]
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