Rewiring your fuel pump [Merged 9-6]

[onegee]

oookkaaayyy....i've must have had 50 do-its to 50 dont do-its ..now that everyone confused the hell outta me...i just want one question answered...

im keeping my setup (in my profile) for now except for a 190 walboro im getting ...now when i install that and turn up the boost on my 14b to 16 psi...would i need the rewire? and also when i get my big16g w/ 550s, FMIC, and afc and turn it up to 20psi, would i REALLY need the rewire? im just concerned about this relay failing business..how likely is that?

plz respond..thanks in advance

 

[ProjectGSX]

I only had 12.3 volts with the stock wiring. I did the re-wire 2 years ago and have never had trouble with the relay.

I also have a pretty beefy sound system, and while at full tilt voltage to the fuel pump through the stock wiring was inconsistent.

 

[Arro]

Originally posted by DrZiplok
If you're planning on upgrading your pump, a rewire is definitely recommended.

And frankly, if you're going through the effort involved in replacing the pump, a rewire is such a trivial thing...

Really? Why is that?

I added the simple Denso 190 into my car. Huge improvement, datalogging is no liar, and I had much more fuel to work with. NO REWIRE.

I think what was said about older cars with geriatrich wiring probs is true, it provides a clean conductor for the power supply, but otherwise if the wiring is pretty much in order, it probably is wiser to just get a pump.

255lph wal-mart pumps shouldn't require a rewire.

Not that I'll ever need a 255. I'll stick with the Denso 190, thank you.

 

[miragetbo1997cc]

I would think that when the car and pump are under heavy load and not idle ,the voltage could drop.Rewiring improves the flow of electricity to a "larger"pump that would draw more amps.Especially at nite time sitting at a light idling .My car isnt a dsm, but when I rewired my Walbro 190, the fuel pump started pumping harder .You could hear the difference.I would think its worth the while.Youd'd have a harder time installing speakers then doing this mod.

 

[Bohrn]

oh, the mod was done, then I posted

In the process of wiring, I tested the voltage to make sure I got the right wire, and lo-&behold, 14v !! But under load, maybe its ok.

Of course some wise types have said that it is not a good idea

 

[doug]

In order to get more fuel to the engine, why don't more people do this instead of getting a bigger pump? Seems like a better answer, but I wanted smarter people's input.

http://www.dsmtalk.com/forums/showthread.php?s=&threadid=68149

 

[MaineDSM]

It just WORKS!!!

I did the rewire in my '96 Talon TSi AWD, and the base fuel pressure went up by 1.5psi! (on the stock pump) Hey kids, that's means it's flowing more fuel. I also did the multimeter test, and got below 12v before the rewire, and 13.x something afterwards.

On my car, it really did work.

Oh, and I've never had the relay blow. Although I know people who have.

 

[onegee]

why do the relays blow and how do i prevent that?

 

[Snoop-GST]

I know its prob a stupid question. and at what point should this mod be done?

 

[Tallen]

the fuel pump for some odd reason is not rnning at 12v. this hops the voltage up to 12v, which lets the pump work better.

 

[cucumber]

And thus, allows you to up your boost.

 

[CL MaNTis GST]

Originally posted by Snoop-GST
and at what point should this mod be done?

anytime u plan on running above stock boost.

 

[doug]

Some people report no change in voltage after the rewire-- so for some it's unnecessary. If there was a way to check your voltage at the pump before you do the rewire, you may find there's no need. At least, that's what I've read in other threads at various boards...

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=17397

 

[DSMJim]

I was only gettting 12.1 or somthing like that on my car, after the re-wire it was upto 13.5-6 and with a 255 now it sending most of the fuel back to the tank , so there's not much point but oh well...

 

[DrZiplok]

Originally posted by onegee
why do the relays blow and how do i prevent that?

Relays can fail for a bunch of reasons.

- Overload. Typically this involves switching too much current, eg. a short circuit.
- Repeated switching, especially of an inductive/reactive load like a pump. In the case of the DSM fuel pump, you can get this if your control-side wiring has an intermittent open circuit (bad wiring).
- Contamination. Water in particular is bad, and the trunk can be a bad place for this.
- Physical damage. Same as for water, the trunk can be a bad place for this.

When it comes to selecting and mounting a relay for your fuel pump:

- Buy a name-brand relay. Bosch, Hella, Delco, Potter and Brumfield... There are others, but those four should get you something reliable.
- Mount it off the trunk floor, and somewhere it won't be knocked around. The same goes for your wiring; keep it out of the way and use sleeving to protect it.
- Take extra care with your wire connections. If you have to use crimp connectors, try to find someone that will sell you the AMP ones with the seperate sleeve inside the crimp, and borrow a proper crimping tool. The connector kits you can buy at auto parts stores aren't very good, and unless you are *really* careful you will make bad joints.

HTH.

 

[Silent2g]

just a tip for you guys who did a rewire
KEEP a spare piece of wire in the car with the connectors on the end of it to have just in case the relay dies
it will die, its only a matter of time.
im still torn between the fact of redoing mine

 

[Bohrn]

yea, I actually thought of that

I have a spare fuze for the 10guage wire, and a small jumper wire so that I can just unplug the stock wires from the dead relay, and plug in the jumper wire.

So far so good tho.

 

[RS/377]

Relays can fail for a bunch of reasons.

- Overload. Typically this involves switching too much current, eg. a short circuit.
- Repeated switching, especially of an inductive/reactive load like a pump. In the case of the DSM fuel pump, you can get this if your control-side wiring has an intermittent open circuit (bad wiring).
- Contamination. Water in particular is bad, and the trunk can be a bad place for this.

I have a few things to add to this thread.

One, it seems to me several people don't really understand the relationship between volts, amps, ohms, and wire size.

As sad as it may be, as an electrician, the best analogy I have heard, and the one I use most often, is comparing volts and amps to water flowing from a hose.

Volts can be thought of as pressure, while amps is the water you are trying to push through, while ohms (resistance) is the size of the hose. The amount of water you actually get out of the hose is watts.

You want more water, either increase the hose or the force behind it.

The problem with wire is that you can force more amps through it than you should, and the heat from the resistance eventually melts the wire. So, when you install a pump that needs more power than the stock unit, you need to install either larger wire or do the relay mod.

About the relat failure, if you overload the relay, you chose the wrong relay, and the failure was preventable. If it shorts, generally you have a bigger problem, and the loss of the relay is an innocent victim.

About the intermitent switching, you could add a little insurance by running a seperate control wire from a different source to the switch, then again, you probaly should tackle the nightmare of poor wiring head on.

About the water, my relay is sealed, can't remember the brand, but this is probaly something that you should look for.

Personally, I'm not worried about mine going out, I've seen a lot of relays live longer than a lot of cars in worse conditions.

BTW- Allen Bradley makes relays also, you won't find them in auto parts stores, but may be worth the extra effort

 

[T6Rocket]

I did the rewire on my old Talon when I had the fuel system pretty maxed out for the stock lines, etc. I did gain a little voltage.

Best to test the voltage, then decide, but really only needed if fuel volume is questionable.

In other words, if you have a 16G & stock motor, not needed. IF you have a 20G & built motor, stock lines, look into it!

Al

 

[onegee]

so im planning on using a big16g at 18psi with a 190lph with 550s and an afc....

DO I NEED IT (the rewire)?

so confusing......but really do i?

 

[HighPsi91]

What part of test your own fuel pump voltage is so hard to understand?? No one can tell you if you need it or not with 100% certainty. Take a voltmeter hook it up at your pump, go out and run your car, and watch what the voltage does under high boost. Thats the only way to know. But as AL, myself, and others have said if your running a big turbo and beefed up fuel system then a rewire is a good practice.

 

[smokehouse_83]

If everyone is so worried about the relays why dont you just rerun the stock wire with a bigger gage wire? I dont know why this wouldnt work the same as running wire from the battery to a relay. Isnt the problem in the size of the stock wire causing too much resistance? Also does anyone have any 3000GT VR4 pumps for sale? Email me if you do.

Drew

 

[Freddy]

I don't have the knowlage or experience to comment on the benifit or lack there of from rewireing the pump, but what I do know and some of you have touched on it, but not stated it clearly is this. Voltage is the pressure pushing electricity, current is the amount of electricity flowing. When bigger wire is used the voltage should be close to same it's the current that is increased. Think of it like this- A 1 inch water pipe under 40 pounds of pressure will flow a lot more water then a 1/2 inch water pipe under 40 pounds of pressure.

 

[doug]

Which is precisely why I asked the question that I did in Post 24 (though I realize you're talking about the wiring, not the actual fuel line). Instead of just slapping on a big-ass pump to push fuel through the stock filter and tiny banjo bolt on top of it, why not just get rid of that major restriction? Seems like a better solution to me, from what I know about it, and I don't know why more people don't do that.

 

[Laguna739]

I was reading the vfaqs and i want to do the fuel pump rewire, but they don't have it for a 2g AWD, only a 26 FWD, so my question is, is it the same process? And if anyone from colorado sees this and is near the denver area and would be willing to help, id greatly appreciate it, cuz im a little nervous about it. thanks all