Very poor supply voltage to the fuel pump, i know most of the wiring on FD\'s are on the small gauge side, but thats not good, so i will be re-wiring that asap, The undersize wiring on these cars has been mentioned on a few threads, particularly the one where it seemed feasable that the small gauge wiring introduced when some alarms are fitted,can lead to engine failure, now i\'m wondering if this could also cause problems with running lean! imagine insufficient voltage to the pump to start with coupled with an often forgotten partially blocked fuel filter! Waste of time trying to tune an Apexi under those conditions surely! worth checking your volts guys,
Bob
That\'s very worrying. I\'m in the process of direct wiring my pump and changing my fuel filter before mapping again!!
I had the same concern and rewired mine direct from the battery into relay. There was a step by step how to on this here or on FDUK. I have an uprated fuel pump on mine and after doing this mod i had a small leak in fuel line.
I think that was caused by pump getting good above 12volts from the point of ignition turned on and the pressure was too much within the fuel lines so one of the clips holding the hose could not hold the extra pressure. I had to disconnect the direct feed from the battery till i sorted out the fuel hosses.
I have since replaced all the fuel lines and used proper JB clips and will be doing the same mod again over the weekend to see what difference it makes...:Hammer
To quote Chuck Westbury ===
QuoteWhen I rewired mine, the voltage at the pump went up by 2 volts from 11.8 to 13.8 with the engine running. This equates to an increase of power to the pump by 37%. Use 12 gauge or larger wire. We are creating parallel paths for current flow which reduces resistance and increases voltage.
I take from that the voltage will be vastly improved from 9.2 to 13.8! my pump won\'t know whats hit it! i will be running an extra earth to the pump also, then measure the voltage again,
My concern is how many other FD\'s out there are running a weak fuel supply!
Bob
Mines got a weak supply too, going to be doing the same in the very near future too. Wouldnt have known if it wasnt for a friend knowing how to use the pfc commander better than me! By the sound of it its probably a fairly common problem!
how do you check the voltage to the fuel pump using the PFC?
no idea, Matt - Arrouk on here found it on mine, ive no idea!
Didn\'t know you could check the voltage to the pump with the pfc,
I used my digital voltmeter,
Bob
As far as i am aware the fuel pump wire is 3mm or 4mm. Does depend waht it goes through though:( Infact I know that Max\'s silver car still runs on the stock wiring.
Doesn\'t the FD run the same set up as the Cosmo low voltage to the pump at low revs then steps up at high revs. A resistor block is wired into the pump wiring to cut the idle voltage to the pump then its bypassed at higher revs giving full pump voltage when required.
Kevin
The 9.2 volts is normal at idle and low rpm.
When the engine starts there is a 12 volt feed which drops to 9.2 and then as Kev say\'s it steps up to 12 at revs to increase the pump speed.
Regards
Carl
Phew! Many thanks for that Carl, Kev, that settles that then, mine is normal!
Bob
Well iv\'e tried revving it, no increase in voltage to the pump at all, still 9.2 The earth to the pump is very small guage! so guess i will rewire it after all, will let you guys know the results,
Bob
Quote from: ro284Well iv\'e tried revving it, no increase in voltage to the pump at all, still 9.2 The earth to the pump is very small guage! so guess i will rewire it after all, will let you guys know the results,
Bob
exactly, and i had the same result....i will also be rewiring mine to see what my injectors readings are on high revs on the commander???
Don\'t quote me on this but i would it is also boost sensitive as even at high revs with no or low boost very little fuel is required.
Kevin
The engine must be on boost and revs at the same time yes.
Regards
Carl
The resistor is underneath the brake servo. Disconect this and jump the Fuel Pump Relay, then conduct your voltage tests again. You will be measuring what the fuel pump is seeing when the engine is under load.
Carl, am i right saying you can check the voltage on the pfc comander? Was having a play around with it last nite and while i did find a page with numbers seemingly in volts, Im not very sure
I believe that voltage on the display is at the battery and not the fuel pump.
what should the fuel pressure be on idle anyone??
I have the same problem with my stock fuel setup on my fd.
I took the fuel feed pipe of, with fuel pump running over a jug and it was tricking out! I could easily stop the fuel with my finger tip.
my car has not run for 3 years , ive rebuilt the motor and I guess its picked a load of sludge up in the filter out of the fuel tank, or the pump is goosed.