dieseling....

[happycamper]

Just when I think I have the truck in good order, something else rears its ugly head. Tired of having my credit card continuously bleeding... here is the gouge:

- had carb issues, (need holley carbologist help thread). Bought new holley 4160 600cfm. Carb seems to be dialed in.
- had issues with timing, set them back to factory specs. 8 BTDC
- have electronic ignition; its all new stuff.
- motor is brand new w/enough miles for sufficient break-in.

Now, it is dieseling when I shut it off. Wondering if the plugs were fouled by the old carb for which the floats stuck and it was pumping enormous amounts of black smoke in the garage. Or, could the water pump be crapping out? Engine feels like it is running hot, even though the gauge says otherwise. Thought about getting an old spray bottle out to mist some water down the carb while it is running to clear the carbon that may be in the combustion chamber....any advice is appreciated, I can't tell the old man.

[70_F100]

What's your idle speed?

[onetuford]

What electronic ignition are you running?

[woods]

Either your fuel mixture (idle mixture) is off causing you to open up the idle screw too far and exposing ports in the carb that are not supposed to be exposed during idle. Or your combustion chambers are running too hot, not the coolant temp, the chambers.

[happycamper]

Hopefully, I can sum up all the other replies here at once...
- Accel ignition; no previous problems, put new plugs in + diz cap today
- Idle speed is about 650-700 rpm in park. About 550 in drive.
- Carb was pre-adjusted from factory, I changed mixture screws to about 1 1/2 turns out w/vacuum meter readings.
- No previous issues with dieseling.

Maybe I got some bad gas. That is not uncommon here in my neck of the woods. I just filled up earlier today after changing the cap and plugs, so maybe this is all coincidental somewhere. Not dieseling now. I'm thinking there is some relationship to the vibrations I've been unable to fix too; I did determine that the motor is missing around 2000-2400 rpm, making me think the vacuum advance diaphram is bad. Will need to check it with my vacuum pump.

Now the battery is dead...been fine for months...

[woods]

Your charging system is putting out around 14 volts? If it's not working, this will cause a miss when your battery starts to drian.

[hotrodfeguy]

Maybe I got some bad gas. That is not uncommon here in my neck of the woods

Start with this and run some good stuff in it and see what happens. The go for the idle screws lean it out till it tumbles when hot then back out till it just runs smooth. It will not be happy till warmed up fully but should stop the diesel shutdown issues. If not look into going two jet sizes smaller on the primary side. This will burn off the carbon in the chambers at highway speeds.

[george worley]

I doubt that it needs rejeting,if it has not been apart stock jets usually are #64-66 which should be okay, Try shutting it off in drive ,see if that helps .If it does your idle speed is still to high.

[woods]

Here is what can happen. The idle RPM does not necessarily have to be too high for your throttle plates to be open too far. This can be caused by a lot of things, including sluggish timing (which you have). If the initial timing is set forward and the vac advance canister is hooked to manifold vacuum (and adjusted correctly) your current idle setting will be way too high, which will make you close the throttle plates more to achieve the idle you want. This will ensure that your throttle plates are not open to far and exposing too much of the transfer slot. Also, slow timing causes combustion chamber temp to rise. If you have some oil coming in or carbon, it helps it light the fuel. This is one scenario. Of course, your truck will run a lot better this way, but that's not what we are talking about.

Second scenario is that you might be running after-market valve covers? Many of these do not have a proper oil baffle to keep your PCV from sucking oil into your intake. This will cause pre-ignition and run on.

Third, you may have carbon build up which is staying hot after you shut the engine down, which in turn will light the fuel. Higher octane fuel is not something I would normally recommend for your engine, which is low compression, but it would probably stop the run on until you drive it enough to get the carb burned out of it. Then you can go back to regular.

Also, if the easy stuff fails, I have seen a manifold gasket cause this. An internal vacuum leak can pull in a little bit of oil and make it keep running.

I really feel that having your timing and distributor set up correctly (which will make you have your carb set correctly) will probably stop all this.

[woods]

Yep and that solenoid was there for when they started retarding the heck out of the timing to pass smog.

[hotrodfeguy]

I am running 62 jets in my 600 Holley

[woods]

I am running 62 jets in my 600 Holley

Nothing wrong with that. If it runs good, does not ping and has no flat spots, then being able to run smaller jets is a good thing.
Typically...I find when I am jetting with a wideband tuner on a rolling road dyno...the jetting comes out quite a shot lower than everyone else runs. My old truck runs a mildy built 428 and my jetting is closer to what many guys run on a hot 390.