Walbro fuel pump high current draw

[slez001]

Hey everyone, first post! I really need some sane input.

I'm finishing up an LS1 swap on my 1990 convertible, and the Walbro GSS340 fuel pump I installed to feed the engine draws around 9 amps at 60psi. Fuse 11 is 7.5 amps so it won't do. My question is has anyone run into this and how badly did their car catch on fire after putting a 10 amp fuse in its plac? From the fuel pump wiring schematics (if I'm even reading them correctly) the smallest wire thickness in the circuit is 1.5mm, which is around 15AWG and should take 15 amps no problem. Am I nuts, or will it run fine with a ten amp fuse?

This is the schematic I've been looking at: https://www.r3vlimited.com/board/sho...d.php?t=195470

[ForcedFirebird]

Use the stock fuel pump signal to trip a 30amp relay and 14awg wire directly to power the fuel pump (fused at 20amp).

[ak-]

I've been using a 10amp on my 255lph for 3 years so far since the 7.5amp kept popping.
Will update if car is on fire.

[ForcedFirebird]

I've been using a 10amp on my 255lph for 3 years so far since the 7.5amp kept popping.
Will update if car is on fire.

Wasn't going to go that far on internet advice, but the endurance car has been running 2 pumps (both sides of saddle tank) for ~8yr, no issues....and it still has the 7.5 amp fuse. :/

[ak-]

Wasn't going to go that far on internet advice, but the endurance car has been running 2 pumps (both sides of saddle tank) for ~8yr, no issues....and it still has the 7.5 amp fuse. :/

What kind of wizardry is this?

The TRE 255lph that I have maybe demands a higher current I suppose.
I had an eBay Walbrobro 255lph on the stock fuse as well for about 2 years before it died, (to which then I found out it was eBay junk) so maybe I have some reading to do.

The gauge of the wire in the e30 is rated for the +2.5 current I believe though.

[ForcedFirebird]

1360-1 and 1320-6

You are correct. Not sure how, but I have 2 cars running dual fuel pumps off the stock relay. This says the fuse is AFTER the relay...

http://wedophones.com/Manuals/BMW/1988%20BMW%20325%20-%20325i%20-%20325is%20Electrical%20Troubleshooting%20Manual.pdf

Not sure, but it does.

My initial thinking was: Early models have a lifter pump and high pressure pump, both being powered by the green/violet, so I followed suit. One saddle feeds the other (no resistance from pressure, it just transfers), I didn't do the "Y" to a single to the regulator.

Either way, it works.

[slez001]

1360-1 and 1320-6

You are correct. Not sure how, but I have 2 cars running dual fuel pumps off the stock relay. This says the fuse is AFTER the relay...

http://wedophones.com/Manuals/BMW/1988%20BMW%20325%20-%20325i%20-%20325is%20Electrical%20Troubleshooting%20Manual.pdf

Not sure, but it does.

My initial thinking was: Early models have a lifter pump and high pressure pump, both being powered by the green/violet, so I followed suit. One saddle feeds the other (no resistance from pressure, it just transfers), I didn't do the "Y" to a single to the regulator.

Either way, it works.

Yeah the pumps draw current as fuel pressure builds. So one of your pumps, depending on how you have it configured, is hardly taking any power at all to run because its not fighting pressure buildup. If you're still running stock E30 fuel pressure (~40psi) then that doesn't draw too much current either. Totally believable that you could make that work.

My problem is that the GM fuel injection system runs at 60psi, and that brings up the current draw of any fuel pump. I'll drop a ten amp in. If it turns out I need more juice or I smell toast then I'll run the wires. The relay isn't stock anyways, everything on the engine side of the C101 is new and will take 20A+

[ForcedFirebird]

Kinda familiar with GM, otherwise "Firebird" in my username would be irrelevant lol.

I doubt you will triple the current demand with a 50% increase in pressure, but an additional relay would easily cure it. :p

[slez001]

Lol point taken :)

Walbro publishes the current demand curves for their pumps. If they're accurate then a 10 amp fuse will cut it

[slez001]

The 10 amp is blowing too. Gonna have to run wires. I measured resistance across the pump and it's only showing me 1ohm, so it makes sense that it would pull 12A I guess??

[slez001]

Any ideas on fashioning a new connector for the pump?

[ForcedFirebird]

The stock wires are tiny and long. Just use the stock FP wire to trip a 30 amp relay and 14awg wire.

...did I mention relay? :p