L20 Dieseling problems

[Runslikeapenguin]

I've been working on my room mates truck and i just did all you standard tune up nonsense, plugs, wires, cap, rotor, oil etc etc and I was hoping that this would some how fix the run after the truck has. Whenever the truck is shut off it diesels a few times before shutting off. Now with all the new ignition equipment it does it even worse. It ran yesterday after it was shut off for a full 6-7 seconds.

 

The truck has a weber DGV and an offenhauser manifold, but pretty much everything else is stock. And to be honest it was dieseling before i took all the smog equipment off and installed the new carb.

 

I've tried 91 octane and I've tried a booster to bring it beyond 91 but it was the same thing. I'm going to go set the timing and the valves today so that might help, but besides that I'm stumped.

 

Any thoughts?

[lil89ram50]

check the fuel pressure.... get a fuel pressure regulator. webers need 2.5- 3lbs of boost.. if its more than that it will diesel like you are saying

[Runslikeapenguin]

check the fuel pressure.... get a fuel pressure regulator. webers need 2.5- 3lbs of boost.. if its more than that it will diesel like you are saying

 

Good point, i knew about the pressure issue but never bothered with a regulator because it ran so good without one. I will check that ASAP.

[datzenmike]

Factory L20Bs run hotter than previous motors so Nissan installed an idle cut solenoid to stop the flow of fuel to the idle circuit when the ignition is shut off to help kill the motor. I'll bet your Weber doesn't have one.

 

If an automatic, shut off in gear then place in Park. If a standard, hold brake on, place in 4th or 5th and lift the clutch just enough to lightly load the motor and shut off. Takes a little practice to do quickly and smoothly but is a 'cheap' fix.