Fuel pump wire guage

[pins999]

Hello all:
I think this might be my first post, and I want to start off by saying thanks to all the great contributors on this forum. I have been following it for many years and finally pulled the trigger on a MK4 roadster kit last year. I have used the search function hundreds of times to get almost all the information I need to help with my build.
That being said, I do have a question about fuel pump wiring. I have a Gen4x Coyote with a 340lph in-tank fuel pump that I am wiring the way FF wants me to in the instructions (Coyote PDB controlling Ron Francis harness relay via coil wire).
I was planning on using the rear harness and pump connection at the tank as it has the proper end and is ready to go. My worry is the wire gauge isn't heavy enough for the 340lph pump. I know it's protected by a 15 amp fuse at the RF end but I'm wondering if I am going to be blowing fuses if the pump draws too much. If it does then it will be hard to upgrade the circuit to heavier wire/fuse at a later date. I have seen some builds that use the supplied harness and connections, so maybe I'm overthinking it...which is normal for me lol.

Thanks for any insight!

Adam

[JimStone]

Wow, joined Aug 2014 and this is your first post! Ultimate lurker! :D



I'm not an electrical guru, but I'm also using a 340lph pump so I just upgraded the wiring to 8AWG while installing the rear harness. I'm sure overkill. I did splice it to the kit-supplied fuel hanger connector. So, yes, that last few inches will not be beefier, but at least the long portion will be.

(Full disclosure: I haven't actually ran the system yet, so you should probably wait for more experienced people to comment)

[lewma]

I've suffered melting wires/connectors with my 340lph pump. Totally due to my oversight of using crappy connectors. My pump runs at 17amps but the connectors I used were rated at 15 amps. I think they were cheap ones so perhaps 15amps was being optimistic.

Just review your wiring and connectors from pump to power on the power side, then pump to ground on the other side. Make sure your wires are big enough and use good connectors or crimps along the way.

While you're at it, make sure the cooling fan has good wire and good quality connectors too. That too can run 15+ amps when running.

mark

[gbranham]

I have a 340lph pump, using the RF harness wiring. No issues.

Greg

[edwardb]

340 lph is a pretty high rate pump for a Gen4 Coyote. Unless you're boosting or whatever. I've run 255 lph in my Gen 2 and Gen 3 Coyotes with zero issues. Supposedly good for up to around 650 HP. The single throttle body crate version of the Gen 4 has the same HP and torque rating as the Gen 3. I've used the stock wiring with my Coyote builds with no issues. A 340 lph pump might be pushing it. The easy way to re-wire would be extend the Coyote control pack fuel pump wire to the pump. It's good for up to 40 amps. The only issue with bypassing the RF fuse panel is it takes the inertia switch out of the circuit.

[narly1]

According to this chart 12 gauge should be OK but you could jump up (in current carrying capacity) to 10 gauge.

213606

Earl

[pins999]

Thanks all.
Yah been lurking a long time! I usually find all the answers I need with a good Google search!

To be honest, now that I look at the Ford Control pack installation instructions again, they state 175LPH at 65psi. I did a ton of reading before I ordered the pump and could have sworn I needed the larger pump, but now I realize it's probably way overkill. I think it was because the FF Coyote instructions state "255 LPH or 350 LPH in-tank fuel pump," and I thought bigger is better!

I was thinking of running the Ford control pack wiring to the tank and wire in another relay with the inertia switch hooked to the ground at the tank. I guess it's that or order a smaller 255lph pump, which is maybe a better idea anyway. Feels like the larger pump will be working hard to just bypass a lot of fuel back to the tank.

Adam

[rich grsc]

The more fuel bypassed, the more the fuel warms up and gets aerated

[Rian_Colorado]

I have 2 cars with 340-355lph pumps (one is a Gen 3 Coyote). I worried about the same thing. Then I checked the gauge of the wiring that was on the pump from the manufacturer.... it was the same gauge as the RF wire. Wired both to the RF system as is, and no issues at all.

IF you WERE to increase the size of the wire, I would change the system and add a relay back near the pump and trigger it with the RF wire (bypassing the relay in the RF system)

Rian

[CraigS]

I agree w/ your concern. Late last summer I added an extra rad fan on another car controlled by a manual switch. All literature on the fan said run a 30 amp circuit w/ 'X' (forget the exact #) gauge wire. Well crap, I kept blowing the 30amp fuse. Over the winter I ran new wire a size larger and changed to a 40amp fuse. Problem solved.

[i.e.427]

I see more often than not folks believing a Walbro GSS340 is a 340 lph fuel pump. It is really a 255 lph fuel pump.

https://walbrofuelpumps.com/255lph-walbro-gss340-intank-fuel-pump.html.html?srsltid=AfmBOop0p9QqB6LHWmgbnl2W17l mMJbVdvPV8j9S19NJrnWU6s74Rt6L

The wire size for the fuel pump in the RF harness is a 14 awg. This is fused at 15 amps. In most cases this will run the fuel pump with no issues. I will however say this. Ford used a 14 awg sized wire in the SN95 Mustangs but fused the circuit at 20 amps. This was do to raised amperage when fuel is forced to deadhead up against the FPR when the engine goes from open throttle to closed throttle abruptly. It only happens for a brief second or two but the increased amperage of the fuse keep it from blowing before the FPR allows the fuel to free flow back to the tank. A standard GSS340 pump will only draw 11 amps when running but 15 amps + when fuel deadheads. We ran into this issue on a Mk4 a few years ago and now place a 20 amp fuse in every EFI car we do with the RF harness.


https://www.youtube.com/watch?v=cMhRghg699U&list=PLDlFwXKm54odKK20vUjltPhPOvuCOobee&index=2

Frank

[Presdough]

What about using the supplied circuit to control a 30 amp relay?