Fst_Byrd

iTrader: (5)

Hey all,

Trying to get the wiring for dual pumps ( lift pump and external pump)

I'm running a surge tank, with an external Carter 4070 as a lift, and a Bosch 044 as primary pump.

I made this diagram below, can anyone confirm if this is the best way to wire both pumps to run all the time? As in... is it as simple as just splitting the harness lead from the PCM into the two relays?

pdxmotorhead

In general, assuming a straight up "on-Off" PCM signal, your looking pretty good,
only things I would do are:
1. Use either a small hard plastic ACCY fuse block, or use fusable links don't use those rubber inline fuse holders.
2. Home run the pump grounds, use 10G or 8G wire for power and ground for the pumps. less heat and more amps to the pump.
3. Use 50A Relays if you can.

Another note,, just cause,, I've worked on a lot of cars trackside, Road race, drag, circle track..
Surge tanks have been the bane of my existence. Next to sloppy electrical wiring they are
probably the most common reason I see a DNF, most common side effect is when the lift
pump quits, it causes the pressure pump to burn out too.. . YMMV, and good luck!

Fst_Byrd

iTrader: (5)

Thanks for the quick reply!

I am building a standalone fuse block so running the pumps through there shouldn't be hard.

8 gauge seems a bit large, isn't standard 12 or 14 gauge for fuel pumps?

Bosch 044 is rated at ~15A and I'd assume the Carter even less. I have 2 40A relays I planned on using, think they will suffice?

Old Geezer

iTrader: (3)

Pcm supply +, or ground signal?
As for the relays, we try to use an 80% rule. Size the relay, so it is loaded to 80% of rating.