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Engine "desieling" ?


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Hey, just brought a 76 Datsun 620. Slowing working out the kinks and restoring my new beauty, I am currently having a problem that has been described to me as "desieling". When I turn off the key to shut the pickup off, it tries to stay running, not sure what it could be! Any ideas?? :confused:  

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A problem with L20B motors Nissan fixed by having an idle cut solenoid. It allows fuel to the idle circuit when the key is on only. Shuts off with the key. No fuel, no run on.



If you have a Weber carb replacement it may not have this feature OR if your idle is set too high it won't work.

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Yes, what Mike said.  By the way, If you look at Mike's profile pic there, just above it it says "King Rat".  He's earned that, based on his knowledge.


We love pictures, and we can generally tell whats going on from a picture.


Here is how to post pics:



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Which Weber?  It could be the 32/36 which should already have the idle cut off switch or the 38/38 which does not come with the cut off switch.   Get us a picture of the carb from the front of the car, and we can identify it pretty easily.  I've got the 38/38, I tried once to adapt the idle circuit cut off switch but was unsuccessful in my first attempt.  I just got the carburetor dialed in, so I plan to make another attempt.  There are other things that might also cause the Weber to do this.  For one, the speed screw ( the one you use to set the idle with);  if it is screwed in more than 1/2 turn from the point where it just makes contact with the throttle lever, then it could cause your issue.  Also, if your float is set too high, or your fuel pressure regulator is set too high, it could be pumping too much fuel into the float bowl and causing your issue.  Weber uses two different floats for the downdraft carbs.  Each float is set differently depending on which one it is. 


If the carb is a 38/38, then there will be one brass adjusting screw on the lower portion of the carb on BOTH sides, left and right.  The 32/36 has one adjusting screw.


This may help:



In the mean time, you can do this:


When shutting off the car, slowly let out on the clutch as you turn the key off. This will use the clutch to slow and stop the engine.....  This isn't all that great on the clutch, but it's better than the engine running on.

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Just to clarify, not all 32/36 webers have an idle cutoff switch. I have had a handful of em and only one came with a cutoff switch.




Well you can order then pretty cheap...


Just when I start thinking I'm getting to know how Weber works, I'm told differently...  One day, I will have all the answers like Mike.

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Herr Diesel, if he survived being kidnapped by the U-Boat in WW1, would be offended by the misspelling of his name. Just pulling your leg, has nothing to do with the technical aspects of this posting. Good luck, hope you now can shut off your engine and not have to wait while it decides to go to slep.

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  • 2 weeks later...

I don't have a weber, I have dual SUs, my engine diesels with the best of them, I don't even think about it anymore, I have better things to think about.

I just come to a stop in front of my house, and while still in gear I just turn the key off and let out the clutch and step on the brake at the same time, then I set the E-brake, it doesn't diesel at all.

I have been doing this for so long, I don't even know I am doing it anymore.  :)

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