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Fuel Pump Voltage

Hey guys I have a problem with my aus spec vr4 which is causing my car not to start. It appears that the fuel pump is not receiving enough voltage and when tested with the multi-meter it was only receiving about 6 volts. To check that this was the problem we supplied power directly from the battery to the fuel pump and then successfully started it. The annoying thing is that it is an intermittant problem as sometimes it will start fine, other times it might start breifly then cut out or other times it wont start at all. I have tried the fuel pump rewire that is on vfaq but to no avail. Would the relay still need a strong enough signal from the car for it to function properly? I have also tried replacing the ECU.
Sorry im not overally good with cars but any help or ideas would be greatly appreciated.

Cheers
 

Terry Posten

Well-known member
Joined
Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA
You may have an issue with the MPI relay. It may have become resistive.

Can you swap another one if to see if that fixes the issue?
 

I had a similar issue a while back and I had some guy come out and fix it...$600 later he told me it was the relay and it seems the way that he fixed was by splicing in an aftermarket relay into the existing wires however, the old relay is also still in there. This worked for over a year and you can feel the relay click on however I still tried replacing the aftermarket relay with another one just to be sure. Can anyone tell me where the power to the fuel pump is supplied from?
 

Terry Posten

Well-known member
Joined
Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA
You could just fix it ugly by finding a power source that is switched with the ignition to power a new relay and that relay can provide straight power from the battery to the pump.
 
Last edited:

The power is supplied through the ignition switch to the MFI relay. Have you checked the voltage at the fuelpump test terminal under the hood while you have the low voltage?

 

Car is running again now but i dont have a lot of confidence in it so when it dies next I will check it out.
Cheers
 

Quoting keydiver:
fuelpump test terminal




Everytime I go looking for that thing I can never find it.
 

There are lots of posts on it, with pictures, if you search. Its just a single female spade terminal with a heavy black plastic insulator on it, right by the VIN plate on the firewall.
 

dsmless

Well-known member
Joined
Jun 12, 2008
Messages
224
Location
tucson,az
i had the same problem on my car, what i did is just run a wire from my fuse box with a 15 amp fuse inline to the fuel pump relay ( I have the rewire kit also) and pluged it into the middle terminal on the relay, this way whenever the ignition is on the pump is on, its easy and cheap, and can still use the turdo timer
 
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