P8 pro wiring fuel pump

Wiring best practices and loom building technique
Benmk1
Posts: 15
Joined: Wed Jul 17, 2013 3:35 pm
ECU Model: P8 Pro

P8 pro wiring fuel pump

Post by Benmk1 »

Wondering how the fuel pump relay works does the Ecu give out a signal to keep the fuel pump on? Also I'm running to fuel pump low and high pressure, how would i go about wiring both pump can I just used the terminal and splice it twice thanks ben
stevieturbo
Posts: 3578
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: P8 pro wiring fuel pump

Post by stevieturbo »

The ecu provides a ground which you will use to energise a relay ( or multiple relays ).

In short, it will be grounded when the ecu sees the crankshaft rotating, and also for a few seconds on key on to prime the system.

In the event of an engine stop ( ie crash type of scenario ) the pumps should stop running

Basically the same way all modern cars operate.
Benmk1
Posts: 15
Joined: Wed Jul 17, 2013 3:35 pm
ECU Model: P8 Pro

Re: P8 pro wiring fuel pump

Post by Benmk1 »

So what part of the relay do u out pin 41 to the earth which is pin 30 under din standard? Thanks Ben
welshpug
Posts: 130
Joined: Tue Sep 06, 2011 4:53 am
ECU Model: S40 Pro

Re: P8 pro wiring fuel pump

Post by welshpug »

Earth to ecu, switched live to other side.
stevieturbo
Posts: 3578
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: P8 pro wiring fuel pump

Post by stevieturbo »

Typically terminal 85 is the relay ground. You will wire pin 41 of the P8Pro to this.

Relay terminal 86 would have a switch 12v ignition feed.

Then the fuel pump power in/out across the other relay terminals 87/30, wired/fused as appropriate
Benmk1
Posts: 15
Joined: Wed Jul 17, 2013 3:35 pm
ECU Model: P8 Pro

Re: P8 pro wiring fuel pump

Post by Benmk1 »

Thanks alot for the reply helped alot would u recommend the best relay to use is the Bosch one in the wiring diagram thanks Ben
stevieturbo
Posts: 3578
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: P8 pro wiring fuel pump

Post by stevieturbo »

Any generic relay of suitable current rating for your pump will be fine.

Cheap or quality is entirely up to you.
Benmk1
Posts: 15
Joined: Wed Jul 17, 2013 3:35 pm
ECU Model: P8 Pro

Re: P8 pro wiring fuel pump

Post by Benmk1 »

Just a normal 4 pin would be good then, thanks alot for your help 10amp will be the fuse in the pump and using a Bosch 044 and facet underneath the car so i just use two relay same wire on both be sound? Thanks alot for your information
katana
Posts: 455
Joined: Sun Jan 27, 2013 6:08 pm
ECU Model: S60 Pro
Firmware Version: 29

Re: P8 pro wiring fuel pump

Post by katana »

I'd go 15A on the fuse - a 044 can pull 11A on occasion!
stevieturbo
Posts: 3578
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: P8 pro wiring fuel pump

Post by stevieturbo »

katana wrote:I'd go 15A on the fuse - a 044 can pull 11A on occasion!
An 044 will be pulling around 11A operating normally. Higher if higher fuel pressures are used.

My pair of 044's on startup. ie key on, and then engine start see a current spike up to about 32A only for a split second though.
Then they settle down to about 22/23A, that's at about 47psi actual pressure.

The spike would never blow a fuse, but I'd still be inclined to run a 20A fuse

For a long time I did run a 30A blade fuse, but you could see that it had been heated and melted slightly. Although it was in use for several years.
Ive re-wired things now with a 40A fuse and 70A relay.


But yes you could use a single 30/40A relay and suitable fuse for both pumps.

You could either run both pumps off a single fuse or fuse them separately.
Post Reply