View Full Version : Separate fuel pump switch

18-09-2011, 02:06 PM
I am currently in the very early stages of building my Rallye into a 'tin top' race car
But looking round the pits in my mates last race, all the very prepared, ex touring cars in the pits have a switch for ignition/ecu, one for cranking, but they also have 'fuel' as a switch.
I was wondering why you fun a separate fuel pump switch on a race car?
When running stand alone I have always wired the fuel pump, along with the Coil and injectors, off a relay switched by the 'fuel pump' output from my Omex.
Now I'm guessing they run the fuel pump off a switch on the dash, I was wondering if anyone knows the reason?

18-09-2011, 03:37 PM
Separate the circuits.
If one goes down then it doesn't take the whole lot out.
That's the only reason I can think of!

18-09-2011, 04:05 PM
but even if only one goes down, youre knackered anyway!

18-09-2011, 04:12 PM
To look cool ;)

18-09-2011, 05:02 PM
It is a bit pointless when it can be ECU controlled, but alot of people don't bother to wire it up that way. Alot of the competition cars have fully functional spare pumps, that obviously demands an extra switch.

18-09-2011, 05:20 PM
but even if only one goes down, youre knackered anyway!

But it's easier to diagnose any problems.
If they are all on the same circuit and the fuse goes it will be harder to trace the problem.

18-09-2011, 06:09 PM
Fused separately, they should be, ECU operation of the fuel pump relay is isolated enough.

20-09-2011, 07:39 PM
It could well be a service pump switch. We run them on all the builds we do. For defuelling the car, have a dry break on the fuel rail, a matching hose, and then just flick the switch

20-09-2011, 08:28 PM
Aah, right!
Thank you for all the replies!
As I said I was struggling to think of a reason and just wanted to make sure I hadn't missed anything.
I'll probably just switch mine off the ecu!

20-09-2011, 08:38 PM
I have my fuel pump running off a switch on the Mini, just to cut the fuel off in an emergency. And to look cool! ;)