Engine dieseling after shutting off

[Ewhitaker0020]

My truck is a 84 Chevy K10 with a 305. I just put in an Edelbrock performer intake and 1406 carb.

I finished putting my engine back together and after some adjustments it finally started running pretty smoothly. When I shut off the key, the engine kept running, but very badly. I've heard of it called dieseling before. It sounded very bad for the engine, like metal knocking.

The engine was running at 190°f it might have been running a little fast, but I don't think it was running rich as I had the idle mixture screws adjusted pretty lean.

I don't know what my fuel pressure is, but I never had this problem with my quadrajet.

Overall the truck is running so much better. I do not know what the timing is, because I don't have a timing light. I moved the distributor around some, but I couldn't tell if it was making a difference or not so I'm just going to quit messing with it until I can get somebody to time it.

 

[legopnuematic]

Get a timing light. Sounds like its too retarded and the throttle blades at idle are open too far. Timing itself doesn't cause dieseling, rather the adjustments that get made to the carb at the improper timing setup to get it to run right. As when timing is retarded the idle speed drops and thus the throttle must be opened to (idle screw) up the idle as it needs more fuel due to poor efficiency.

So get a timing light, or borrow one, set base timing at 10 degrees advance to begin with and then using a vacuum gauge, after idle speed is corrected, set idle mix screws to where the engine draws the most vacuum at idle.

 

[Frankenchevy]

Ditto, get it timed then adjust the carb. If you’re considering paying someone to time it, just get your own light. These are great and allow you to check base and total timing on anything without an indexed balancer or timing tab. Although your factory tab will likely have something for 8 or 10 degrees.

You must be registered for see images attach

https://www.amazon.com/INNOVA-3568-...=2025&creative=165953&creativeASIN=B000EVYGV4

Here’s an article on adjust idle fuel mixture for a qj, there may be better tutorials out there:
https://itstillruns.com/adjust-idle-screws-quadrajet-carb-7557958.html

 

[roundhouse]

Also try using higher octane gas
And get the idle set as low as you can
If you have AC get the electric solenoid that bumps the idle up so the AC and drive won’t kill the engine

If nothing else works
And you can always just switch off the engine while it’s still in drive , the drag on the engine will usually prevent the dieseling

I used to have a 69 thunderbird with a original 429 cobra jet engine and in the summer I had to leave it in drive when I switched it off , then shift to park.
93 octane helped but didn’t cure it

 

[Ewhitaker0020]

Get a timing light. Sounds like its too retarded and the throttle blades at idle are open too far. Timing itself doesn't cause dieseling, rather the adjustments that get made to the carb at the improper timing setup to get it to run right. As when timing is retarded the idle speed drops and thus the throttle must be opened to (idle screw) up the idle as it needs more fuel due to poor efficiency.

So get a timing light, or borrow one, set base timing at 10 degrees advance to begin with and then using a vacuum gauge, after idle speed is corrected, set idle mix screws to where the engine draws the most vacuum at idle.

I'm borrowing a timing light tomorrow. The truck is running so much better. I got it back together and drove it to town. I've got a bad exhaust leak that I'm going to have looked at as soon as possible.

 

[Ewhitaker0020]

Ditto, get it timed then adjust the carb. If you’re considering paying someone to time it, just get your own light. These are great and allow you to check base and total timing on anything without an indexed balancer or timing tab. Although your factory tab will likely have something for 8 or 10 degrees.

You must be registered for see images attach

https://www.amazon.com/INNOVA-3568-...=2025&creative=165953&creativeASIN=B000EVYGV4

Here’s an article on adjust idle fuel mixture for a qj, there may be better tutorials out there:
https://itstillruns.com/adjust-idle-screws-quadrajet-carb-7557958.html

There's so little room to check the timing on this engine. Every YouTube video makes it seem so simple, but with the water pump and pulleys it's very hard to see the harmonic balancer.

 

[Arkansas_V8]

My old Suburban dieseled for a bit. I checked everything 100 times. It ended up being the carb gasket.

 

[Ewhitaker0020]

My old Suburban dieseled for a bit. I checked everything 100 times. It ended up being the carb gasket.

I fixed the dieseling problem. It was probably that I had it idling way too fast. Ever since I idled it down I haven't had this problem.