why everyone should rewire their fuel pump
 

How many of you have put a volt meter on the fuel pump on a dyno? I saw something scary this past week. Car I was having tuned had 550s/1680s, aeromotive fpr, supra tt pump, new oem fuel filter. Should have been enough fuel for close to 500 rwhp.around 16 psi boost we hit 100% injector duty cycle. Base fuel pressure was 40 psi.Car should have had injector to spare. I watched the fuel pressure gauge and under boost it shot to 60 psi and by 5000 rpm started falling. Fuel pressure fell as low as 40 psi.This explained why we had to add so much fuel at the top of the map. Next I put a volt meter on the fuel pump and was shocked to see just over 11v! Made no differnce if it was at idle ore wot. Car has a new alternator and odyssey 925 battery. Voltage on datalogit was over 12v at all times. This shows how much voltage drop there is in the junk factory wiring, As these cars age and are tampered with it gets worse.The fuel pump should have over 13v. This is another reason motors blow.

I agree, I removed mine from the ign harness first thing.

I did this as part of my battery/fuse relocation project:

Battery -> Circuit Relay -> 30A Inline fuse -> Fuel pump

Why 30A? I just used the stock 20A.

Does any one have a diagram of where it ties in (fuel pump)?
dale`s web site is not up and i seem not to find that fuel pump write up.

Yeah, I mean...JEBUS! 30 amps! :scratch:

Any write ups on how to do this?

Do you remove the factory wiring or do you add wiring in parallel?

The fuse should be ran for the wire size, so if he ran a 10 gauge wire, then a 30 amp fuse is fine. The fuse is only to protect the wire.

I gotcha, I didn't run new wires I just changed the source.

ok so.from battery run 10g wire with 20v fuse in between to #30 on the relay.Then cut the stock supply line to the fuel pump and run 10g wire from #87 relay to stock wire pump side.then run 10g wire from #86 relay to the car side of the stock supply line. is this correct?

and this bosh relay can be found by the fuel pump under the fuel pump cover is this correct?

Is a full rewire really necessary? Ive only done the simple one DaleClark posted up. Has anyone actually ever had that setup perform poorly? Seems like alot of work if there is already a proven simple solution.

FWIW
http://www.reganrotaryracing.com/fddualfuelpumps.htm

Regards,
Crispy

The other nice thing about rewiring the pump is that say you are using the standard wiring system, and the car is running/tuned well. If the speed relay or the ecu driver for the speed relay fails you will have no way of knowing. The pressure will fall, you could lean out and boom.

The bosch relay has to be purchased. I prefer to run a new wire especially since i'm running dual pumps. This bypasses all factory wire and connections so you know it's the best it can be, but either method works.

where is a good source to purchase this bosh relay and is there a specific one?

Any place that does car audio and alarms should carry them.

it doesn't have to be a bosch relay any 4 or 5 prong relay will work. Just make sure the red/wht wire goes to one of the coil side's of the relay, and ground goes to the other. This will make sure the relay is activated the same as the stock fuel pump is. Then the switched portion of the wire goes between the battery 12v+ and fuel pump. It's really simple.

If you want to go all out you can run a new wire off the pump and connect it to the relay instead of using the other side of the red/wht wire that was cut. Here's how I ran my wire.

http://i10.photobucket.com/albums/a1...87ddd31782.jpg

http://i10.photobucket.com/albums/a1...c30a35ba70.jpg

I have also rewired my fuel pump the way Dudemaaanownsanrx7 has shown. Fixed all my fuel problems I was having before. Dudemaaanownsanrx7, how did you seal those power lines going intank? I just used a rubber grommet like the one you have and used a bunch of slow drying epoxy.

thewird

Your guys need to watch those wiring penetrations in the fuel pump cover. Those little rubber grommets will wear over time and the last thing you want is a short to the cover with fuel vapors right there = kablammo

Crispy

I used fuel safe sealant to seal both sides of the grommets in. it's not shown in the picture. I don't see any possible way for my grommets to wear, they are sealed in and don't have any movement. I'm not worried about them, I do good work.

:) I have no doubt you do.

Regards,
Crispy

lol thanks

ugh more stuff to do lol, keep it coming, the more i learn the longer my engine will last lol

my list of "to do's" keeps growing and growing

Don't forget about jumping out the resistor pack. If you don't the system could still send low voltage to the relay and it won't be able to pull in.

For anybody that has not done this, what the hell are you thinking, just do it, it is a very simple fix and you get the peace of mind that you will not damage something at wot.

where is that resistor pack located?

Definitely be careful with the grommets going through the pump carrier, I've seen an instance of fuel wicking up the wiring into the back hatch area......

or you can use this

http://www.cj-motorsports.com/catrx7twinwalbro.htm

You can run an extra relay or jump the wires in the front fuse box like Dale Clark wrote about. Only problem with the later is if you have a problem in the harness somewhere up front, it will still persist in back.

Especially a prob in hot areas like Fla if you have a faulty purge system.

I just de-pinned and re-attached my own wiring to the factory bulkhead.

Under the master cylinder.

It should also be noted that your fuel maps will be running richer in all areas now. My cruise map went a full point richer, I don't recall what the boost areas were because I just retuned everything.

recently performed this mod with the diagram posted on page one. Thanks for the diagram :icon_tup:

my idle fuel pressure went up about one psi so i assume that the pump is now getting the required voltage thought the powerband and not just at idle :dunno::dunno:

i really wish i could do this but i dont want to mess with my electrical system, i would love to do it tho

hey simon wanna come do mine? i would guarantee id mess something up

+1 for doing this mod if you are making any kind of power. It's worth the time/effort!

-ch

This I haven't heard about. What are you actually doing? What does it do?

If this wouldn't screw up my tune, I'd do it.

The stock FD has a resistor that lowers the fuel pump voltage at idle/cruise to prolong pump life. If you jump it, it will have full voltage all the time.

thewird

hey Rich, do you know if you can purchase replacement electrical plugs for the connections on top of the fuel pump cover, or do you need to buy the whole harness?

yeah just give me a call ......its pretty easy as long as you follow the diagram

The last owner of my car just jumpered the fuse box up front. What should I do about this if I do the full re-wire that dudemaaan posted on the first page.

problem with the resistor bypass is that you are still using the long and dry car wires. You only gain that you are full voltage all the time but at WOT or where the higher fuel consumption is necessary, you won't gain anything from this since the stock relay is already triggered.

So it is a pretty useless mod. You better rewire it completly with a new relay and a new wire directly from the battery.

You mean he bypassed the stock relay in the box in the very front of the car? Just leave it like that, you can still install a new relay in the trunk with a new wire to get the better voltage.

Do this mod now!
 

I re-wired my fuel pump and my car ran so incredibly rich I had to pull TONS of fuel out on the dyno. The car stumbled and fouled the plugs just by rewiring the fuel pump on STOCK injectors and STOCK fuel map on PFS PMC.

I ended up being able to run 16psi on the dyno making 330RWHP up to 7500rpm with a 10afr out of rewiring the pump. I would never run this on the street of course at 100% duty cycle but the point is, DON"T mod anything on your car until this is done.

Hell, this is a mistake, pumps should be directly wired from the factory. Think of all the possibilites and hassles of having inconsistent fuel pump voltage....this is probably a hidden cause of many engine failures...people thought their base map was enough fuel, but the pump wasn't getting enough volts.

Here's another nice thing about rewiring your pump. You get another 12v switched in the interior fuse panel that doesn't get killed during cranking.

+1. The resistor bypass should only be done after removing the fp source from the ign harness if your not going to run a new wire.

The resistor bypass alone won't help much. I like to get rid of it mainly to simplify the system and eliminate a possible failure point. I got a full extra volt at the fuel pump by running a direct fused 12v wire from the battery to trigger the fp relay.

Yeah that's what I was asking, I'll go ahead and snag a relay and start doing this right. :icon_tup: