# 84 Datsun/Nissan will not idle



## lofarris (Jul 9, 2006)

My 84 Datsun/Nissan Truck with a 2.4 liter 4 cylinder will not idle after it has been running for 15 minutes or so. Last week it died on me while driving and looked like it was not getting any gas. I don't know if the fuel pump was dying or it was vapor locked but the next day it started right up, only to do the same thing 20 minutes later. I replaced the fuel pump and filters, cleaned out the carb, verified there were no vacuum leaks and added some gas treatment. It started right up and was running smoother that it has in the last 3 years. After about 15 minutes again, it died at several stoplights, but it ran great as long as I wasn't trying to idle it. I took it home and adjusted the idle rpm from 350 to 650 per spec in the manual. It is still doing the same thing, it runs great and idles very smooth for about 15 minutes then it gets real rough, puffs a lot of black smoke thru the exhaust for about 10 seconds and then dies. I can pump the gas a couple times and starts it right up. The truck only has 97k and the plugs, wires, distributor and all vacuum hoses have been replaced in the last year. Anyone have any suggestions?

Thanks in advance


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## Ant-dat (Apr 20, 2005)

i had a problem like this on an old nissan laurel it turned out to be the metal pipe that passed across the front of the engine. somehow (still not sure how) it was letting air to be sucked in causing a air lock in the fuel i replaced the pipe and the car was sorted
not sure if that will help or not but might be worth a try


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## blownb310 (Jun 10, 2002)

Welcome to the boards lofarris,

Your post really belongs in the "Truck and SUV" forum but it's good to have you on board anyway. If you say the truck belches black smoke and then dies I'd have to say its too rich or flooding. The next time it occurs, I would pull over, get out, raise the hood, and look at the sight glass on the side of the float bowl in the carburetor. There is a "bullseye" in the middle of the glass where the fuel level should be. If you don't see the fuel level in the sight glass, it's either way too high or empty. What I'm saying is your needle and seat might be sticking and not maintaining the proper fuel level in the float bowl. If the bowl is empty, you might have a bad fuel pump control unit. That unit is located very high up the passenger side kick panel, to the right of the glove box. I have seen them go bad and turn the fuel pump off intermittently. They are a bear to diagnose if you aren't aware of them. I used to work at a dealer that's how I know. I think I still have a new one in the box here somewhere, left over from the old days. I remember the old 720 trucks well. 

Mike


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## lofarris (Jul 9, 2006)

Thanks guys, i will check both ot those this weekend.


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## foodstamp (Nov 29, 2005)

I had the exact same problem with my truck a couple yeaes back. At first I thought it vaporlock, but it wasn't the problem, the problem turned out to be the fuel pump relay.
I replaced the fuel pump relay and the problem went away and has been running great ever since. The easiest way to figure out if it's your relay is the next time your truck stalls like make sure your key is in the ON position and then just listen to see if you can hear if the fuel pump is pumping or not. If its not pumping then the problem is with your relay. I hope that helps you out, if not then Good Luck to ya. Please post a reply when you get it fixed to let us all know what the problem was.


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