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Fuel pump fuse keeps blowing

1079 Views 3 Replies 4 Participants Last post by  collegekid
I have a stock 1990 nissan 240sx se, all stock other than EGR, radio, and AC delete.
I keep blowing my fuel pump fuse every time I turn it on. I've replaced the fuel pump, fuel pump strainer, fuel filter, and made a hardline for the fuel pump. the fuses kept blowing before on the chassis harness before I even did the hardwire. then i changed the pump, filter and strainer and it ran fine for 1/2 month(s). then the harness fuel pump power from the harness became unresponsive so I did the hardwire. the hard wire worked fine are 1 month, then suddenly one day every time i turn the toggle switch on for the pump, it primes for one second the fuse pops.
Im running a delphi OEM replacement pump.
OEM fuse I used was 10amp and the hardwire fuse kept blowing 30amp fused
This has been my issue for the past 6 months. if anyone knows anything let me some insight on what could've gone wrong.
I am currently going to rewire my fuel sending unit, replace the pump and strainer.
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There has to be short somewhere in the wiring you didn't replace, but that still interfaces with the pump somehow. I'd start tracing and shooting wires at this point.
Silly question but have you checked all your grounds? I had a truck that liked blowing fuses until I went through and grounded everything. You could also start running continuity checks through everything…. Sucks but sometimes it’s what has to be done
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I am here to echo my man RikRong. You have a short somewhere.

The fuse blows when it detects too much current ( amperage) in the circuit.
The circuit is designed to only allow a certain amount of current to pass through.

Your battery wants to get rid of all of it immediately, and your car is designed to only allow certain amounts to go through certain circuits.
That's why you see those movies with torture scenes where they touch the red and black wires on the battery and it goes BZZT.

You have some part of that circuit that is grounding itself somewhere. It's happening somewhere in the circuit after the fuse. Think about it, if it was happening before the fuse, you would just have a dead battery all the time. So you need to follow the wiring from right after the fuse all the way back to the fuel pump. You probably have an exposed wire on some bend that the insulation has worn off. Your entire chassis of the car is connected to the negative battery terminal. So any exposed wiring is essentially doing that torture scene BZZT and blowing your fuse.

I don't have any idea where it could be. I suggest you download the factory service manual, look through the electrical section and check it out.
The wiring snakes through the car. It could be as simple as some wire (positive power wire) rubbing through the insulation on a bend, OR you messed up your wiring. That's extremely dangerous.

As far as wiring for the fuel pump, I have not done a hardwire mod, but holy hell I don't think you're supposed to be using a 30 amp fuse unless all the wiring has been upgraded to handle 30 amps. On an oem size pump you do not need that much amperage so you need to be back at a 10 amp fuse or whatever the stock size is. Again, I don't know crap about it, I'm on stock wiring/stock fuel pumps on 2 cars, and my sr20 car is on a walbro 255 on stock wiring.

Something else I can think of, what kind of shrink tubing are you using?
Because the regular home depot crap isn't fuel and oil resistant.
I used one of these, might have been the fuel resistant one.

Please be careful with what you do. Let us know how it goes.
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