dannyual777

There appear to be so many options out there that when I do a search, my head starts spinning. I decided that maybe it's best to narrow this down to see what other Fox body swap people have done to fuel their LS engines. For those of you not familiar, here is a link to my Project "Hole in the Head"

I'll list some of the Cliff notes here:

1991 Mustang Coupe, brand new GM LS376/480 crate engine, brand new Tremec T-56 Magnum, complete Maximum Motorsports suspension including torque arm and panhard bar and Holley Terminator LS MPFI Kit 550-611 computer system.

I also have a donor car that I ordered brand new; a 1991 Mustang GT (ocean salt-water rust damaged and no longer driven since 2016) that is giving up a lot of it's good parts to the coupe, i.e. rear differential and black interior.

So I have two perfectly good Fox gas tanks so I'd like to use one. Around 2014, I replaced the fuel pump in the GT's tank with a brand new Walbro 190lph pump. It's bit on the small side and it's been sitting in stale gasoline for 5 yrs so it needs to be replaced. I know there are plenty of in-tank pumps that I can use.

My question is how I should wire up the fuel pump? I currently have the GT's very good wiring harness in the coupe. In other words, the fuel pump relay under the seat is in place as well as the inertia switch in the trunk. Should I keep it the way Ford wired it? I'm a little concerned because that fuel pump relay under the seat received commands from the OEM EEC.

dannyual777

For fuel line, I'm planning on bending and flaring tubing like this:
I've read a lot of good things about this tubing but I have zero experience with it. My car is currently high up on jackstands and now would be a great time to run the fuel line.

dan95gst

in my new edge ive got 10awg running to a 40a relay thats triggered by the holley then back to the fuel pump in the tank. my fuel pump basket in the tank was dissolved because the car sat with e10 gas in it for 7 years and the plastic was just flaking apart. so the pump is just dangled into the tank with the pickup towards the back. works fine for a drag car but not ideal for something thats gunna be turning. i put some AN bulkhead fittings on the tank hat and ran new lines up to the front.

a 250lph pump should be fine for an NA LS. if you are going boost youll want more.

dannyual777

dan, you replaced the new edge OEM wiring with your own 10awg and a 40 amp relay. Maybe I should just run my own new wiring and do away with the OEM Fox fuel pump relay and inertia switch? Sorry to hear that your plastic gas tank basket dissolved due to crappy ethanol gas. I'll check the parts inside my tanks when I remove the current fuel pumps.

I wasn't sure how much bigger than 190lph to go on the pump but 250lph sounds like a good place to start.

dan95gst

yep, replaced all of it. the new edge PWM the fuel pump which i had no desire to do. depending on how many amps your pump draws, you can feed it directly off the holley. the instructions tell you the max amps draw.

Michael Yount

iTrader: (1)

Deatschwerks DW300 intank pump -- quality piece, so quiet you can barely hear it prime. Check Fox wiring size to see if it's sized appropriately to drive whatever pump you choose. If not - replace. The pump should be fired off by whatever ECU you end up using. Any relay sized to handle the load should suffice.

dannyual777

I'm looking at my Holley Terminator instructions right now. It says, "Green-Used to directly power a fuel pump (+12 volt). Do not use this wire to power fuel pumps that require over 15 Amps. For high current pumps, use this wire to trigger a separate relay and use larger gauge wire to fee the pump-10 gauge wire is recommended...."

Alright, it sounds like I should forget about the 30 yr old Ford OEM fuel pump relay and fuel pump inertia switch. Run new wiring to the new fuel pump that will either be powered directly by my Holley Terminator or via a relay.

dannyual777

Michael, I'll take a look at that fuel pump online. I'm going to just run new wiring and forget about the OEM wiring that's currently in the car.

dannyual777

340lph in-tank fuel pump w/ 9-1014 install kit


I think that I'd better just plan on running a relay that's controlled by my Holley Terminator 550-611.

Michael Yount

iTrader: (1)

My GM E38 ecu fires a Bosch 30A relay which drives the DW300 pump. 4.5 years of flawlessness or flawlessivity if you like.

dannyual777

I'm sold, Michael! I think I'm going to order one of these pumps today or tomorrow. BTW, did you use a genuine Bosch relay or a "Bosch type?" I know that there are plenty of relays available everywhere but they're probably china made. I'd pay more for something not made in china.

Michael Yount

iTrader: (1)

Oops - old memory not serving. I had the Bosch on it when I had the Ford 5.0L in the car. When I put the LS3 in, my PSI Conversions harness/relay board/ecu provided the relay, so I'm not sure what brand the current one is (5 years ago). Whatever PSI Conversions puts in their boards....I just ran the output of their relay into the pump/wiring circuit on the car.

dannyual777

Thank you for the update, Michael. I have a leftover relay that I used to fix the "Foxbody fog lights on with headlights on" problem. This whole wire harness came out of my donor, 1991 GT and I can use it in the coupe. With no fog lights on the coupe, I can use the relay for the fuel pump. If I need more relays, which I will since I'm rewiring the headlights, I'll try to find non-china made relays. I may be looking for a very long time .

64post

iTrader: (5)

340 liter per hr HyFuel pump in the Fox body tank with Holley Terminator X turning it on and priming with key on, it’s just too easy, one wire, one fuel line, no return.

dannyual777

64post, I've taken a look at that pump and it looks like it would be great. I'm going to have to give this system some serious consideration: HY-FUEL Single Pump in-Tank Retrofit Kit