9.2 volts at the pump!

ro284 · February 06, 2007, 04:47:27 PM

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

dre · February 06, 2007, 04:55:43 PM

That\'s very worrying. I\'m in the process of direct wiring my pump and changing my fuel filter before mapping again!!

Laeeq · February 06, 2007, 04:59:07 PM

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

ro284 · February 06, 2007, 05:45:13 PM

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

andyroi · February 06, 2007, 05:54:22 PM

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!

Kash_ · February 06, 2007, 06:46:14 PM

how do you check the voltage to the fuel pump using the PFC?

andyroi · February 06, 2007, 06:58:30 PM

no idea, Matt - Arrouk on here found it on mine, ive no idea!

ro284 · February 06, 2007, 07:27:50 PM

Didn\'t know you could check the voltage to the pump with the pfc,
I used my digital voltmeter,
Bob

cjr · February 06, 2007, 09:36:16 PM

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.

kev-yorks · February 06, 2007, 09:40:36 PM

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

Carl · February 06, 2007, 10:16:56 PM

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

ro284 · February 06, 2007, 10:21:36 PM

Phew! Many thanks for that Carl, Kev, that settles that then, mine is normal!
Bob

ro284 · February 08, 2007, 04:00:52 PM

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

Laeeq · February 08, 2007, 04:11:14 PM

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???

kev-yorks · February 08, 2007, 08:31:22 PM

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

9.2 volts at the pump!

andyroi

andyroi