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Help! fuel pump doesn't prime. nothing :(

33K views 35 replies 6 participants last post by  Ingo 
#1 ·
Okay, I have a 2004 wrx. When I turn the ignition switch to acces. There is no prime on my fuel pump. Nothing. My engine turn over but doesn't start. I did a voltage check the fuel pump relay by the passenger compartment. With the ignition on accessory. I'm getting 12.3 volts reading from one side but the other side 0.00.

Is it a bad relay? I also check the volts on the harness over by the fuel pump. I get about 6.4 volts. Please help a noob out.
 
#2 ·
Either replace the relay or replace the pump. Your pump could very well be toast.
 
#13 ·
You could have also check your relay before ordering it. Disconnect the connection to FP. When not energized the terminal from 12V to FP/FPC will show open circuit. Then turn power on to energize the relay.
If the two terminal when energized show short circuit or very low resistance, the relay is good if not then toss.
 
#20 ·
Squarish doesn't mean jack, pink is the color code for the amps. Got a wiring diagram or the fuse box cover? should be able to identify what that fuse is for. Might very well be. Next question is "why did it blow?"... Sometimes fuse just go and only need to be replaced, often there is a good reason for it to blow and replacing just results in another blown fuse. Just replace and see what happens, fuses are relatively cheap.
 
#22 ·
Several ways you can go now:
1 take to shop and "bleed"
2 find problem youself
3 replace fuse with high amp, like 50, and see where the smoke comes from...

Really, fuses are there to protect the wiring. The electrical system is quite capable of delivering enough amps to set the car on fire. Fuses are a good thing. Your circuit that feeds the pump likely feeds something else and that something has gone bad. Unless your fuel pump itself draws too much power. It is possible. Try another fuse, this time with the electric to the fuel pump dis-connected. If the fuse holds just fine the problem is likely the pump.
 
#23 ·
I'm in the process of taking my driverside fender out. I'm trying to see if there's a short ground somewhere in there. I have a walbro 255lph, do you think that draws too much power? I had the fp in my car for a a month and haven't encounter this problem before.
 
#25 ·
the pump should not normally draw too much current, it's used often and I have not heard of electrical supply problems. It might have ingested some debris and that might cause it to draw more power. But usually that would block the pump from running and make it not run while drawing over-amps. Unlikely that said debris would just make it run harder, but bot impossible. I still think it worth to potentially "use up" another fuse and see if with the pump's electric disconnected (at the pump) there is still an overload condition. If there is then there's either something else connected to that circuit and shouldn't be or you actually have a wire shorting to ground. You might want to consider getting a multimeter. HarborFreight has as low as $3 or $4...
 
#29 ·
If diodes got fried you'll have to replace with larger ones. The inductivity of the motor causes voltage spikes, especially when power to pump is turned off. The diodes short that induced voltage and thereby protect relay contacts and the rest of the system. The new pump probably causes larger spikes and killed the diodes.
 
#30 ·
I should also mention that there is this transparent sticky liquid all over the circuit board. Probably time for a new one, better one I suppose. What is it? and is that because something might have melted?

Before I took out the fuel pump controller. I bought 2 30 amp fuse to test it. First one I disconnected the fp harness, turn ignition. Fuse blow right away. Then I disconnect the fpc, the fuse blew right away as well. Could be a short somewhere along with a bad fuel pump controller.
 
#31 ·
Update,

Started unplugging all the harness under the hood on my car. Turn ignition switch to on position. Tada, the fuse doesn't pop. Work my way backwards. Found out there's a short somewhere on the manifold wires. Because when I plug the brown harness in by the battery, it pops the fuse.
 
#34 ·
Cool. Thanks for reporting back, so many people don't. Now where and how exactly did that happen? Is the fuel pump supply routed together with the injector wiring or was the short actually in the injector wiring and that's just on the same circuit?
 
#35 ·
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