fuel setup wiring

[markKE70]

Car - ke70

motor - bigport 4age

use - grip and drift

problem - destroying vl presure pumps

occurs/started when - i got it back from teh auto electrician who rewired the whole car

personal situation - want this piece of shit running its doing my head in

as stated above since my car has been rewired it has been destroying the vl pressure pumps, the current setup is a vl in tank lifter feeding surge tank, then vl pressure pump.

at first i just thought i was getting unlucky with the pumps (2 second hand from wreakers) and bought a brand new one which then only lasted an hour. ive since taken the tanks out and flushed them, and voltage tested the pump which was getting 14 volts. is this to high?? i assume its only ment to get 12 volts, what could be causing this? as the auto elec is denying that it is his wiring which is the problem.

before there was two wires runing from the fuel relay to the pumps in the boot and the were wired seperatly and now there is one wire and they are linked in together. how have other people on here wired up your fuel setups? because this doesnt look right to me ???????

any help would be greatly appriciated
cheers mark

[trikzlane]

should only have one wire witch is the (+) and the (-) should be grounded to the body.
hope that helps

[slide86]

it shit the new pump?

massive WTF.......

they will have 14v when the engine is running as they will be getting battery voltage, with the alternator charging, it will be 14v. this is fine.

when i wired it, i had a relay for each fuel pump. I think it is too much current draw for one relay to handle, thus i made the circuit with one relay for each pump. i have no idea what the auto elec would have done now tho

[markKE70]

yer man its got me there is deffs only one relay now so yea was looking at my mates 4age setup and his is wired in a circut and his pumps only have 12 volts , this car is a head fuck lol

[sundee]

are you running an in tank pump in an external setup? i was sure that you CANT do this as the intank pumps are designed to run submerged in the fuel which helps them stay cool.
Wiring isnt an issue - its doesnt matter if its 2 wires or 1 wire, you have 2 pumps so the previous person to set it up must have been running a smaller gauge wire in parallel and now you auto elec has upgraded the feed wire to cope with the current flow for the both pumps and wired them in series.

i would also be checking that your lift pump is working properly - you said its the main pump keeps failing? - if the surge tank is not getting enough fuel then the main pump will run dry and again it uses the fuel flowing through the pump to keep it ruining cool, so no fuel = heat + expansion = dead pump!

[slide86]

i wired it the first time.......i dunno why the sparky changed it......the setup was fine, 2 relays large gauge wiring.

the way i had it wired was, large gauge wire straight from battery positive to the boot, split into 2 relays. Relays triggered by ecu and fed power to pumps.
since then tho, it has been changed by a previous owner and auto elec, so myself and mark arent sure what the deal is now.

- the lift pump is a carby 7psi pump that is working well
- the surge tank is always full of fuel...at idle anyways. this is an idea that i had when we were at AJD (pressure pump running dry). but i cant see a 4age using 2lt of fuel that quick
- after the new pump was fitted, the car ran perfect.....i was sure the problem was fixed.....well it was.....until now.

[Schnickles]

As for the voltage 14v is about normal.

Might be worth checking the voltage at higher revs though cos if its charging at an excessivily high voltage it could be problem with the voltage sense wire to the alternator.

[sundee]

i cant see that anything else could be causing the problem unless the alt is throwing out to many volts... mayb the lift pump cant keep up with fuel demand, at idle mayb, but after a good drive it maynot be keeping up supply.
Have you got the Return from the fuel rail going back into the surge tank or the main tank?
it only takes a few seconds of dry running for the pump to die.

[slide86]

As for the voltage 14v is about normal.

Might be worth checking the voltage at higher revs though cos if its charging at an excessivily high voltage it could be problem with the voltage sense wire to the alternator.

True.

The way i have the sense wire is that it is bout 1.5 inches long with a ring terminal on it, and goes straight onto the b+ terminal of the alternator. unless of course it has been changed by the previous owner.....as so much stuff seems to have been.

[markKE70]

well huw ive now put a vl lift pump back in
sundee86: the return goes to the surge tank and then to the big tank the pump definatly isnt running dry as the surge tank is always full. hence why im thinking it is a wiring or voltage issue

[ke70dave]

does the pump make noise?

if the pump is working correctly, it should almost completely silent during opperation.

it sounds like you have exact same setup as me.


any sort of noise coming from the pump will be cavitation, which will be destroying your pump. but they should last longer than 1hr....

try measuring the voltage across the pump when it is running. that will tell you if you wiring is good.

and slide86 one relay can supply about 40A, so its fine for both pumps. so long as your wiring is up to carrying 40A over ~2-3 meters.

[markKE70]

the volatage across the pump when running was 14 volts ill get my mate around today and put some load on it and check it then

the pump is making noise but what would make it cavitate if it has fuel?

[sundee]

^^ not enough fuel will cause cavitation - i still wouldnt rule it out just yet