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Nissan Fuel Pump running while engine is off....

A

Aaron Ford

Well-known Member
95 Nissan KA24e

My truck does a neat trick. It runs fine, pulls fine, stops fine, gets good mpg, but this beats all.

When I park it, engine off, keys out, doors locked, etc... Days later when walking past I notice the fuel pump is running. It runs a while, then shuts itself off. I was working on my tractor one day and noticed it. I have witnessed it doing it several times since. Never drains the battery or causes any problems. You can lay you hand on the tank and feel that it is indeed the source.

But why?

Aaron
 
I have seen a Plymouth Duster slant six all of a sudden start cranking itself whilst parked. Spinning like a big dog it was, but with the ignition off, it was just spinning and running the battery down. Had to take off a battery cable to stop it, then it was normal after putting the cable back on. Wierd.
 
Suspect that the fuel pump is keyed by a pressure switch on the fuel rail in the engine. Normally will shut off a few seconds after engine is off and fuel flow stops. Probably a bad pressure switch. Need to check with a knowledgable mechanic on your particular model.
 
But this should be a switched function, right? Why would it do it with the engine/key off and no crank signal?

I recall some sitting on the trunk of some older luxury cars and having the pump come on and jack the car back up. We had fun with that... I also put a Bulldog remote car starter on my wifes car. When she went to visit her parents, the car would start all by itself at 5 oclock, Monday through Friday. Never on the weekends. Good thing it had a safety switch.

Back to the Nissan, I wonder where the power comes from that runs the fuel pump solenoid. Did not know that there was a pressure switch in the system... Gonna look though.

Aaron
 
I've NEVER seen a pressure switch in the fuel system of a vehicle. (Yeah I know, NEVER say NEVER!)

When the key is turned to "on" the 'puter runs the fuel pump for about 3 seconds, then shuts it off 'til engine cranking is detected.

Some vehicles have an oil pressure switch that will start the fuel pump after a little cranking, if the other system has failed.
 
More than likely Fuel pump relay is bad . Computer grounds relay , relay supplies power to pump . Relay should be on right fender .
 
most vehicles have an oilpressure switch [OPS]that takes over the powersupply to the fuel liftpump after it registers oilpressure. if the contacts fail to release the pump will run all the time,cause there is continues batt power to one side of the switch.the computer only provides power to liftpump via relay on initial start.
 
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