well i havent posted for ages, but have been working on the car..
since i recond my head and had it shaved 1.5mm, once its warmed up and i turn engine off it continues to run for about 10 secs (shuddering) and finally dies.

normally as far as I know this should only happen when motor is too hot. Ive fitted a new temp guage and cleaned radiator and its only running up to about 93 deg, not too hot.

I thought it might be the regular ULP not up to the higher compression and detonating, so filled wih LRP, no improvement.

i have the idle at 1000rpm, that shouldnt be too fast to be causing the problem i think.

any ideas, its driving me nuts

If you are using a stock carb they have a fuel cut-off solinoid ( spelling? ) attached to the carb that is meant to stop running-on. yours may be not working or connected properly..worth atry??

I had the same problem, depending on what year and if you have a stock carby you can check the deisiling solenoid by unpluging it to see if it clicks out. Also check your timing and mixtures. Last but not least use a spray bottle to spray a fine mist across the intake.... sounds dodgy but a mechanic that i work with say's it helps remove some of the carbon from the cylinders??? don't know if it's true but it seem to work?

This is called dieseling, when the engine continues to run even though the ignition is turned off.

Quote:Wow! Why so fast? When Nissan changed the Datsun 1200 to 800 rpm in 1973 (north american models), they added the anti-diesel valve to the carburetor. It was not needed at 700 rpm.

The number one cause of dieseling is extra air (e.g. fast idle). You might also have a vacuum leak if you cannot get the idle any lower.

The extra compression will raise temperatures in the combustion chamber. It's not a problem, but might contribute a bit to the dieseling. This is what people mean by "running hot" -- it's not the water temp, but the air temp going through the engine.

Here's the Datsun document that talks about dieseling:



page 17
Quote:

ok, ive put idle down to 850rpm, and seems fixed. I think lack of backpressure from sports exhaust system makes it run a bit rough any lower, thats why i had it on faster idle.

there are no wires connected to the carby, its an A14 with stock carb in a 1000, so dont know about the solenoid being connected. anyway it seems ok now.

it does burn a little oil, so that should help with extra heat in chambers someone mentioned i think...

thanks.

Glad to hear it's working. Now if I can just stop the dieseling of my own 1200. It idles at 600, but still diesels

The lower backpressure often results in better airflow, meaning you might need to re-jet the carburetor to get maximum power with economy. But none of this affects idle, since you can lean or enrich idle with a twist of the idle screw.