what supplies the fuel pump relay with power? does it get it directly from the fuse box?

 

The power comes right from the battery through an inline fuse so it's hot at all times.
The trigger for the fuel pump relay comes from the ECM.

 

so i must either have a bad relay and/or pump.becuz i can use a screwdriver and make the relay give juice to the pump,cuz i hooked a test light up to fp wires and messed with relay and it lit up.

 

also gets a signal from oil pressure sender that way if you lose oil pressure the pump shuts of and you dont blow the motor

 

This is not correct.
The oil pressure switch does not supply power to the fuel pump relay at all. The path goes through the switch and directly to the fuel pump.
Also oil pressure only closes the switch and completes the circuit, powering the fuel pump. This is a secondary system and in NO way a safety system. It's meant to backup the fuel pump relay.

 

well, thats what i read so i bought a brand new oil switch for 50.00 bucks,and still no go. the relay doesn't click, but if i use a screwdriver and acuate the relay i get power to the pump(test light).even then ,the pump doesn't turn on. probably the dang vats huh?

 

sounds more like a bad connection/ground or bad pump.
If you power the relay and the pump doesn't come on it's either not getting power or it's just bad. VATS won't effect it.

 

BBSR, what's your engine type? TBI? TPI? Once I know that, I can give you detailed troubleshooting instructions on how to find your problem.

Also, feel free to do a search (let's say on "fuel pump") and you'll find a lots of threads with good info on what to check. Sometimes the problem is in the fuel pump connector by the gas tank, sometimes it's in the wires by the relay, it can be many things.

Lou

 

it is a tbi.

 

sorry to jump in but can i ask bigbabylou's opinion?

my 91 z28 350 tpi has an issue that i solved by replacing the fuel pump relay before but 12months later is starting to return.

when i floor it with a quarter tank it starts to lose power like the fuels not getting through, when i fill up the tank its ok.
then gradually it starts to happen with half a tank then goes completely to point that it will sometimes start but die straight after.

i replaced the relay last year but its starting to happen again. could it be to do with the fuel pump? how easy is it to get to the pump? i've got the interior out at the moment & theres a ig black connector where the rear seats were that whines really loud when i turn on the ignition, is this the pump?

most appreciated if someone can help.

 

BBSR72, haven't seen your reply until now, sorry. Did you find your problem?

Sweeneyuk, it sure sounds like a problem in the fuel tank. The pump might have popped out of its holder and might be just "roaming" around or something. This definitely doesn't sound like an electrical issue. Doublecheck a couple more times that it happens only when your fuel level drops.

Lou

 

it was in the tank ,the problem was the hose that connects the pump to the sending unit was swelled up and split down the side.

 

When the issue first starts i notice it only when the fuel level drops but it gradually gets worse until even with a full tank it will start then die straight after.

what does the fuel pump relay actually do?

Where can i get a reasonably priced fuel pressure tester?

Can a fuel pressure gauge be fitted permanently to the fuel rail? think it would look neat & i can always check my pressure really easy.
Thought about screwing a gauge in place of the schraeder valve?

 

The fuel pump relay is there so that the ECM can turn on the fuel pump.

You can try car-parts stores but the FP tester might be $30 or more. I got mine for a few bucks (something like $8.99) on sale at Harbor Freight. True, it's not the best quality but hey, it measures fuel pressure just fine.

Yes, if you find a fuel gauge that can be mounted on the engine, it's no problem to put it there permanently.

Lou