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why everyone should rewire their fuel pump

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why everyone should rewire their fuel pump

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Old 06-19-09, 08:45 PM
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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.
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Old 06-19-09, 09:12 PM
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I agree, I removed mine from the ign harness first thing.
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Old 06-20-09, 12:43 AM
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I did this as part of my battery/fuse relocation project:

Battery -> Circuit Relay -> 30A Inline fuse -> Fuel pump
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Old 06-20-09, 02:27 AM
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Why 30A? I just used the stock 20A.
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Old 06-20-09, 07:25 AM
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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.
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Old 06-20-09, 08:11 AM
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Originally Posted by NeoTuri View Post
I did this as part of my battery/fuse relocation project:

Battery -> Circuit Relay -> 30A Inline fuse -> Fuel pump
Yeah, I mean...JEBUS! 30 amps!
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Old 06-20-09, 11:18 AM
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Any write ups on how to do this?

Do you remove the factory wiring or do you add wiring in parallel?
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Old 06-20-09, 11:35 AM
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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.
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Old 06-20-09, 01:55 PM
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I gotcha, I didn't run new wires I just changed the source.
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Old 06-20-09, 03:12 PM
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Name:  Fuelpumprewire-1.jpg
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Size:  51.1 KB
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Old 06-20-09, 03:25 PM
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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?
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Old 06-20-09, 03:36 PM
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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.
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Old 06-20-09, 05:10 PM
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Old 06-20-09, 05:51 PM
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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.
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Old 06-20-09, 06:29 PM
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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.
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Old 06-20-09, 06:33 PM
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where is a good source to purchase this bosh relay and is there a specific one?
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Old 06-20-09, 07:24 PM
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Any place that does car audio and alarms should carry them.
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Old 06-20-09, 08:13 PM
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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.



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Old 06-20-09, 08:26 PM
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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.

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Old 06-20-09, 08:36 PM
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Originally Posted by thewird View Post
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.

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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

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Old 06-20-09, 09:21 PM
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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.
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Old 06-20-09, 10:00 PM
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Originally Posted by Dudemaaanownsanrx7 View Post
I do good work.
I have no doubt you do.

Regards,
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Old 06-20-09, 10:16 PM
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lol thanks
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Old 06-21-09, 01:00 AM
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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
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Old 06-21-09, 07:05 AM
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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.
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