So when I shut down the motor it likes to start running backwards dieseling.
How to correct this?

Thanks

You're running the Weber 38, yes? Not sure how much this would apply, since I'm running the 32/36, but same principal I would assume.

1. Make sure the fuel/air screw is set correctly. If you bought your carb new, this should be covered in the installation instructions. From what I remember, you have to start with the screw being so many turns out, then with the car at operating temp, turn the screw in until the motor starts running rough, then back it out like a half turn or something like that. That will get you in the ball park.

2. Adjust the idle set screw. On my 32/36, it would diesel at anything above 700 rpms. After you set the fuel/air screw, adjust the idle so it's just a tad above the second line on the tach. Any higher and mine usually would diesel, any lower and the steering wheel would shake at idle. That should get you close, maybe within 1/4 to 1/8 turn on the idle screw. Also, I've learned to use mid-grade gas, that helped a lot with my dieseling issue.

Good luck!

If you are running the Weber carb, do you have a good fuel pressure regulator? Not the dial kind, but a 3-5lb holley? If not Id start there. Good luck, METALMOVER

My '89 Monty with the 2.6L and 32/36 Weber has 170K miles, and runs fine with the stock fuel pump. Start with those carb adjustments first and a tank of mid-grade gas, and see if that cures your dieseling problem. The carb adjustments don't cost anything, and mid-grade gas is what, .10 a gallon more than regular? Give it a try, and see what happens before spending money on a new fuel pump.

This ahs been ocvered before. THe weber meeds a lower fuel pressure than the internally regulated pressure from the mitsu fuel pump. The mitsu pump has two outlets and one suction. One outlet is regulated to around 7-8psi and goes to the mikuni float bowl (high front center of the carb). The unregulated bypass goes to the lower dside front (iirc) of the carb, thru the auz accel pump fuel reservoir, and then to the fuel return line to the tank. You need to put another pressure regulator on the first regulated line set to the pressures noted above.

What is happening is that the fuel pressure is pushing the needle off the seat and overflowing the fuel bowl into the carb throat. The constantly over rich mixture is carboning up the combustion chamber. The carbon deposits get white hot, and ignition source, and the leaking fuel and the ignition source make the engine diesel. Fix the fuel pressure, and then fog water spray into the carb throat with the engine at high idle to remove the carbon deposits, preferably with the exhaust disco'ed from the cat.

The FPR METALMOVR is mentioning is the Holley 12-804. Just picked one up. Hate to say it SoCal1200R but every time I drive this thing I think I'm going to light up with the amount of gas fumes I get on me. Love the rig, tho! Putting the FPR on tonight to see the difference. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Installed a 1-6psi FPR. It did NOT stop the dieseling and caused other significant problems.

That topic is here...

I just noticed the post after replying to this one. Also since then I installed the Holley unit mentioned before. After the "steam" clean I checked the timing, went through the initial settings on the Weber for Fuel/Air and Idle then tweaked to my ears and the results were very positive. Easily a 20% increase in power across the band, no hesitation between 2600 and 3k RPM, after letting it idle (high for a bit then adjusted to 650) the unburnt fuel smell was completely gone. Last but not least... no more dieseling. Just my experience and could be totally different for you if you have different gear(of course). Oh, I had the FPR set just under 2.5lb

Good Luck

Do you have any pics of the install. I am about to try installing the 804 to cure my issues and am interested in seeing where you mounted.

I'll snap some pics this weekend. I need to clean up a lot of stuff under the hood on Saturday or Sunday and I'll get a few for you. Once I pull all of the factory vac stuff out there will be plenty of room on the driver's inner fender whether it's flat or horizontal.

Cheers!