swapped over my fuel pumps today to see if that was the cause of the splutter and loss of fuel pressure once the car had warmed up. Second fuel pump works fine but does exactly the same as the first. Soon as car is hot it intermittently loses all fuel pressure. No particular revs or throttle. Fuel pump then becomes noisier than normal too.

anyways using a multimeter my pal Rob sat in the boot while i was tramping on to see what the voltage was across the fuel pump relay. he said from pin 85 to earth?
he was a bit surprised at the results, the voltage climbs from first turning it over to around 17volts. voltage DOESNT drop when car splutters and loses fuel pressure. now how does it go above battery voltage? and the power to the relay comes from the ecu?

is this right or wtf is goin on?

surely my car doesnt have TWO faulty pumps?

help this is drivin us nuts!

chop

ps car goes REALLY well before fault occurs. tonight was first dry spin ive had since buying the car in august!

 

What voltage do you get at the actual pump when you turn the car over? I found that I was getting 10.8 volts on my escos..... I don't think you should see 17 volts when its running??? The max voltage you should see is the max your alternator puts out to the battery - about 14.5volts - but this can vary....

 

aye exactly what we thought!!!! well i shit you not its 17v! thats taken across the fuel pump relay which Robin says is whats across the pump.

battery voltage is normal 13/13.5volts!

dont know why the voltage goes so high but could this be screwing up the pump?!

aaaaaagggghhhhhhh

 

I would get it checked I don't think the pump should be seeing 17volts!! Damo V for example wired a direct supply from his battery to the pump (including relay & fuse) to make sure he had a reliable 12 volts..... I think my pump is getting about 10-11 volts (a bit low ) - so I am thinking of doing the same as Damo..... Yours is a bit high though...

 

yup very strange! where the hell is the power coming from

 

bump

 

Chop, you need to measure the voltage AT the pump, not the relay.

There will be some drop along the wiring to the boot, the inertia switch etc.

Re the meter, I suggest operator error, if you're sure that the battery voltage isn't 17V too?

Neil.

 

neil
battery voltage is as i said above 13/13.5v or whatever. I dont suspect user error either tbh. Robin will be along here later with his input

still we're fucking stumped

 

any more advice?

Stu perhaps?

 

Chop, have you considered it may be the regulator causing the problem?

Neil.

 

do you mean fuel pressure regulator?

Mike r suggested regulator on the alternator thats why i asked. Car holds high fuel pressure for while after car is turned off so didnt think it was the FPR.

 

OK, fair enough

Just a thought

 

do you agree with me tho? fuel reg should be ok if pressure remains when car is off?

 

std reg as in the sig pic sleeve ? one one of them you know whats?

voltage seen at pump should rise with rpm as far as i can remember. dingo defo tested mine whilst i was sat revving car up (stationary)

 

have asked him for you like the fucking star i am

 

standard regulator yes

i tried msn'in dingbat but no reply. ask him what voltage you should see at the fuel pump relay. pin 85 to earth.

cheers

chop

 

"min is 13.3 volts under load.....

He needs to re-wire it from the battery and check the earth's

also what voltage is at the ecu..."

 

thanks mcbell

 

Chop, this is how I did my pump:

Clicky

There is probably an easier way, but this retains all the standard wiring runs, inertia switch etc, but still has less attenuation

Neil.

 

decided to book it into auto electricians for wednesday. Guy reckons it might be a battery/alternator problem because nothing else could boost the voltage to 17v at fuel relay.

gonna get them to rewire the circuit as neil has done too