Danster76

iTrader: (2)

s2 running efi with external fuel pump.

Battery voltage with engine idling is approx 13.65volts
Voltage at the fuel pump with engine idling is 12.75volts
a difference of 0.9volts

I've been advised to get the fuel pump voltage up.

HOW? any tricks?

Cheers

Karlos G

iTrader: (4)

IMO That's good mate, dont do anything.
Just out of interest who advised you?

Micky

Nothing wrong with 12.75 volts at the pump,perfect!!!!Regards,Micky

orionmojo

iTrader: (1)

Yeah thats good! i had less than 7v at mine

sodding connector blocks and bodges screwing it up. NMS had a fun time on my car

Karlos G

iTrader: (4)

Danster76

iTrader: (2)

I thought it reasonable.
I'll stop before I start then. From what I've looked at of the wiring it looks in good condition.

Cheers for the support!

jodyhoare

*sigh* u still tinkering dan??
is it because i showed u up the other day

Danster76

iTrader: (2)

Always mate.
Seriously, your car went really well and almost kept up...I was running 0.5bar boost though.

When mines set up we'll 1/4 mile them for a laugh eh?

DazC

iTrader: (1)

i personally wouldn't be happy with that! What is the voltage down to under full load?

cozmeister

iTrader: (1)

Should it not be whatever the charging voltage is while the engine's running, ie, ~14.4 volts?

DazC

iTrader: (1)

well if it's already a volt down at idle, something is high resistance somewhere! Higher than it should be. When on boost and the fuel pressure is up another 2 bar and the pump starts to draw some current, that'll drop off more than likely.

cozmeister

iTrader: (1)

Are you still using the original fuel pump wiring? If so, I reckon that's where your problem is.

Danster76

iTrader: (2)

Thanks for input. I'm off to rewire it just now
Will post up outcomes. Am aiming for charging voltage at pump terminals so approx 13.7v...wish me luck

xr2wishy

iTrader: (2)

13volts should be where it's at minimum, even with my ICE i only get 14.1 to the rear through a chunky cable, i think my pumps at 13.8volts, but that is power split between two pumps, so not bad considering the load IMO.

jodyhoare

im only running 10 psi atm m8, im still running in so shouldnt be running any lol
yh a 1/4 would be a good crack buddy, i just had to buy a new battery

orionmojo

iTrader: (1)

Like i said, NMS had fun with my car there.

i'll bet they've broken better examples before

RUPERT THE BIG HAIRY BEAR

try rewiring to see what happens at the volltage on the pump

mercgrey

sounds ok to me its only a 12v battery the alternator puts it up to 14.4 ish so i doubt the pump is ment to run higher than 12 as standard??

DazC

iTrader: (1)

that's irrespective. The whole car will be at 14 volts and the pump is only seeing 12 of that which means something is higher resistance than it should be. This means that there is also a current supply issue to the pump and it can't get what it needs. Voltage is pressure behind the current that is there. Something is restricting the current from flowing, which in turn means the pump is drawing more current through the wiring than the wiring can handle.

mercgrey

my mates mfi turbo has a decent volt gauge in and that read 12.5-13 volts earlyer running on tickover, so his wont be at 14volts!!

my point earlyer was why do you want more than 12volts going through a 12 volt pump? but the only thing you can do if your not happy is run a complete length of new cable and try that!

DazC

iTrader: (1)

it's nothing to do with the pump only being rated at 12 volts. It's the fact that the alternator is producing 13.7 volts so every thing on the car should be seeing that voltage. If it's not, there is a supply or return (earth) issue. Every thing on a car should be seeing charging voltage when the engine is running.

Danster76

iTrader: (2)

Thanks for input fellas. I have rewired the pump from pump backwards into the car. Made a new earth and along this run no longer have any earthing issues but still only have 12.8v ish. I need to check around the fuel pump relay next.

Cheers,

DazC

iTrader: (1)

did you take a supply straight off the battery and return the earth back to the battery? Most of the problems are usually at the front of the car where it joins the loom and some times the terminals on the relay get hot and increase in resistance. It would be worth replacing the relay and putting the positive and earth on the battery. I assume you have used decent sized cable to account for voltage drop across the length of the car? It should have been rated at about 30 amps at least, 2.5 mm cable or bigger idealy.