Fuel Pump Working Sometimes...Need Help

[Briou]

Ok so I have searched and found tons of stuff about fuel pump problems but nothing quite the same as the problem I am running into....so here it is


Having a problem with my fuel pump....this is in my 93 240sx with an sr swap with the AEM computer...When ever I go to start my car the fuel pump doesn't prime...It will kick on once in about every 30 tries and once the car is started the pump runs as it is supposed to....I figured out that if I have the key in the ignition and turned to the on position, then I pull the ing switch fuse and replace it the pump will kick on...I have tested the voltage at the pump when I key on and it hits 13v for a second then immediately drops to 7.6ish...I am charging the battery now to see if that will change anything but until then does anyone have an idea of what might be going on?

[Briou]

Update: I got the batt fully charged and nothing changed....I found out there is some sort of aftermarket alarm system that is tied into my ignition harness so I am in the process of pulling that out...hopefully I can find a solution soon...

[davirene]

Just throwing this out there.....had a problem with a ka starting very similar.....turned out the tumblers were wore out in the ignition switch.

So I bought a new one and had it keyed for my car and bam starts right up....

I am not sure what your problem is...but it dont hurt to check it out....

good luck

[Briou]

Ok cool...thats what my tuner suggested...where did you find a new ignition switich?

[Briou]

Replaced the ignition switch and nothing changed...really scratching my head on this one....

[davirene]

I got the switch from the dealership.....

I would say to check your grounds.....make sure there clean with no rust or grime buildup.

See if you can run a hotwire straight to the fuel pump..... just to see if it stays on???

[Briou]

I checked the grounds and running a hot wire to the pump works...it is something between the ignition and the computer, or the computer and the pump....I just don't get why it will kick on every time if i pull and replace the ign switch fuse....

[Mikester]

Did you try a fresh new fuse? Sounds dumb, but it's cheap & at this point; you got nothing to lose. Also, you may have a flaky connection on the back side of one of the fuse sockets where removing/replacing fuse sort of jimmys it... If it works when you mess with the fuse, that may be the best place to start.

[zombiewolf513]

How old is the fuel pump?

I had a similar issue, sometimes I'd hear it prime, sometimes I wouldn't.

I changed to a Walbro and fixed it.

[Briou]

Mikester: I will have to try that...never really thought of just replacing the fuse to see if that would fix it but what you were saying makes sense.

zombie: I had a walbro in it when this started happening...changed it out and it still does the same thing....