patricklav

iTrader: (7)

Need some help figuring this one out guys!

When I turn the key forward the fuel pump will not prime , nor will the fan turn on. If i run a jumper wire on the relay connector i can get them to turn on. If i hook up a relay (which does work because it works on the high speed blower) the fuel pump and fan still do not come on when the key is turned forward. I tested the relay connectors with a multimeter and have 12 volts hot to both at all times. When i turn the key forward, i see 12 volts on the connector from another wire, so that tells me the ignition is sending the signal to activate the relay but it still will not work.

Any idea whats causing this?

any help greatly appreciated!

thanks

TTOP350

iTrader: (8)

The fan shouldn't turn on unless the computer is seeing a certain coolant temp. (unless someone has hot wired it or the relay isnt working properly)
The fuel pump relay will prime once if it hasnt been primed for a certain number of seconds. (I cant remember how long you have to wait between primes)

patricklav

iTrader: (7)

That explains the fan, but the fuel pump wont even run, even if i start the car unless i jump it from the relay connector.

As far as the fan, how can i wire it so it runs as soon as i start the car?

thanks

88gunmetalgta

iTrader: (1)

Why in the hell would you want that??


I have a "fan 1, auto, both" switch in my console. Everyday driving leave it on auto, at the track I can turn one or both fans on without the engine running. To do that, just wire a toggle switch to ground the coil side of the relay (only one wire out into the engine bay, the other wire off the toggle switch goes to any convenient ground)

Reddfalcon1

I have a similar issue. Tpi has been replaced with a carb and ECM and most electronics have been removed from the car. I can jump power to the fuel pump and it will run. But how do I get it to turn off once it primes. I can't be having my fuel pump run the whole time the car runs. Anyone know anything about.

88gunmetalgta

iTrader: (1)

It ain't all that bad, just can't leave it key on engine off for hours at a time. The fuel pump runs whenever the engine runs on EFI cars anyway.

Reddfalcon1

Yah but I have the factory pump through Mallory regulator down to carb strength fuel pressure won't that burn up my fuel pump running all the time and working hard only to send 70ish% back through the return line?

patricklav

iTrader: (7)

i added a ground switch for the fan.. works great.

thanks

patricklav

iTrader: (7)

The pump isnt working 'hard', its only working as it should. the pump doesnt know whether the fuel is coming back or not.

88gunmetalgta

iTrader: (1)

I ran a v6 pump on on a toggle switch for 3 years back in my dumber days... It survived. I think you'll be fine.

BigBadLou

iTrader: (3)

Falcon, the fuel pump on EFI cars runs the whole time the engine spins. It only produces 40-45 psi of pressure and the rest of the fuel bleeds off and returns back to the fuel tank. This fuel circulation keeps the fuel pump cool. The fuel pump does not know or care how much fuel is being returned to the tank. It just provides its maximum volume and keeps the pressure at the given specs all day long, whether you are idling or racing. The only difference is how much fuel is used and how much of it is returned to the tank.

Patrick, have you figured out why the pump doesn't run? You said it won't run even if you start the car unless you jump it? Then what? Then it runs? Or does the engine stall?

patricklav

iTrader: (7)

Yeah I'm pretty sure it's just bad wiring. The car wouldt even start. It would just sputter and never fire. I decided to power the pump with the ignition on to keep it simple for now.

BTW, your articles on ATG are great. They helped out a lot with some of my electrical issues.

Thanks