I would like to rewire the FB 340 lph fuel pump so that it can receive more voltage, but I have a few concerns. Now, I am not an Electrical Engineer nor do I have a lot knowledge about electrical circuitry so I would like to ask you guys on here what you think.

So with me it’s always safety first. Please refer the attached FB 340 Fuel Pump Test performed by R C engineering and also look at the attached Load Carrying Capacities for different gauge wires below. My concern is if I run the FB 340 at the factory base fuel pressure of 43.5 psi and then boost my car (hypothetically with 20psi of boost). The fuel pressure should increase at a 1:1 ratio and that should put the fuel pressure at about 65psi. If you look at the R C engineering’s test you will see that @ 65psi fuel pressure the FB 340 will draw about 14.2 amps at 13.5 volts. Now looking at the Load Carrying Capacities chart you will see that the stock fuel pump's 18 gauge wire can handle up to 16 free air amps (I am not sure what free air amps mean).

[attachment=20281:Fullblown fuel pump.png]

[attachment=20282:Wire Load Carrying Capacities.jpg]

I know that you want the fuse in the circuit to match the amp capacity of the smallest cable of the branch circuit. You can always go smaller for more protection, but never go larger.

I don’t have a doubt that the stock 18 gauge wire can handle the electrical load produced by the FB 340 fuel pump. So my question is:

Shouldn’t the inline fuse in this circuit (from 8 gauge wire to the relay) use a 15 amp fuse and NOT a 20 or 30 amp fuse because the stock 18 gauge wire can only handle up to 16 amps?

It just makes sense to me that if there is a short in this circuit, the stock 18 gauge fuel pump wires can melt before it trips the fuse. And because there is gas associated with this circuit I can see a future recipe for disaster.

So I am thinking maybe I shouldn’t do this rewire or even use this 340 lph fuel pump and just stick with the walbro. Please give me some insight on this!

I am I thinking crazy?

I was also thinking of another way around this is to install an extra 15amp inline fuse between the relay and the fuel pump along with using the 20amp inline fuse that goes between the battery and the relay.

What do you guys think?

Thanks in advance for any insight on this matter.

 

When re-wiring with the Aeromotive 340 we normally just use a single 15amp fuse inline with the power wire like you were describing, and we have had no issues in the past. Same for any of the aftermarket fuel pump except for the big boys like A1000, Magnafuel etc.

Zack

 

free air means just that... open to air to help keep the heat down. In other words not in a bundle of wires.

 

I spoke with a few performance shops and they said they really don't rewire pumps unless they are asked to do so by the owner. Boosted cars ran fine with stock wiring.

I had Walbro 255 and now have FullBlown 340. Both worked fine. Is this mod REALLY necessary?? I am sure pump performance will be "better" with more voltage but do we REALLY need to do this?

Just asking.

 

No

Sent using free Tapatalk - Android FTW

 

I made 600whp on the stock wiring and FB fuel pump and still had quite a bit more room to play.. Not sure what your power goals are though.

 

if you check voltage at the pump with stock wiring, you dont get 14 volts, thats why we rewire it. sure it will work with the stock wiring, but you compensate for it and the pump runs out of steam earlier. do what you want though. not a big deal. i rewired mine since my battery is in the trunk rofl.

 

You need to find different "performance shops" then.

I saw a big difference, simply on how easy the pump primed when I first turned the key. On stock wiring, it's almost like it's choked.

 

^^i agree.

 

So are most people on here using a 15 amp fuse in this circuit?