Fuel Pump Rewire Do I really need it?

[GalantGreg]

For my new motor, I've upgraded the fuel system with 255 Walbro, and Aeromotive FPR. Is rewiring the fuel pump absolutely necessary? What's wrong with plugging the pump into the harness and letting the computer control it. I'll also be running DSM Link v3 by the way.

 

[talondave]

I never rewired mine and im running 25lbs of boost with pte 780s with no problem.

 

[Boosted98gsx]

Getting better voltage to your fuel pump, and a more consistent amp draw can NEVER hurt. Spend the $15 and rewire it.

 

[toofast82]

Hope this helps!
RRE Instructions
Many have tried to use a 255 with stock regulator and not rewire it as a bandaid for an afpr but you have one so id definitely do it. Its much more consistent voltage and higher pump output. I used to hear my pump change pitch with the turn signals in my first dsm with 255 and no rewire, I dont trust it

 

[Boosted98gsx]

You'll still hear your fuel pump change pitch with other stuff on. That's just due to the horrible charging system of the DSMs.

 

[toofast82]

The rewire is intended to eliminate those issues, i dont hear it changing like before a rewire

 

[GalantGreg]

I understand that it couldn't hurt, but it isn't necessary. Right? I really don't want to do it if I don't have to. I should be getting plenty fuel for my 560's letting the computer control it.

 

[toofast82]

The fact is the stock wiring is so small and doesnt conduct power well. It's like the same gauge as your hair
Would you put undersized wiring for your amplifier and subs?
I don't understand why people dont do this? It takes less than an hour, its beneficial and piece of mind as well!

 

[snowborder714]

Rewiring the fuel pump has nothing to do with the computer. All it does is give higher, more constant/consistent voltages. This allows the fuel pump to maintain higher pressure/volume at all times, whereas it might fall off on the stock wiring at higher boost levels.

No, it is not required. It is a good idea however unless you don't plan on pushing the car.

 

[pboglio]

I think its a good idea if the pump is small. I run the Denso 150 LPH pump and I was leaning out massively at higher rpms running +23 psi of boost. A rewire allowed me to trim back maybe 15% fuel at WOT, without any falloff in 02 voltages at higher rpms.

If you do rewire, be prepared for an assload more fuel and a retune. I could see a Walbro 255 becoming difficult to tune without an adjustable fuel pressure regulator if the pump is rewired. I remember afterwards how slow my ride felt since it was drowning in fuel at WOT. Once tuned the a/f's were dead consistent though.

 

[steve]

Is rewiring the fuel pump absolutely necessary?

No. I hope by now you understand the benefits. The Walbro doesn't draw as much current as the Denso pumps do, so the voltage drop isn't as bad on the wimpy factory power feed but it's still a factor. How important it is will depend on what size injectors you run and what boost you run.

What's wrong with plugging the pump into the harness and letting the computer control it.

Even with the rewire the computer is still controlling the pump.

I'll also be running DSM Link v3 by the way.

That's nice but besides the point.

 

[GalantGreg]

So basically the the wiring harness does not supply ample voltage to support the 255. Is that correct?
Even though my motor is fully built, my plans for my 1g are not too aggressive. Don't get me wrong, I will get up on it every once in a while. I guess it couldn hurt.

 

[steve]

So basically the the wiring harness does not supply ample voltage to support the 255. Is that correct?

That's too black and white. The Walbro 255 draws less current than the factory Denso pump (at least on a 1G) so it's less effected because there is less voltage drop but any pump including this one works better with full voltage and the more fuel your using and the higher the pressure your using it at the more the voltage makes a difference.

So you asked if it was absolutely necessary. The answer is no but there are good reasons for doing it that usually make the decision easy.

 

[me612]

If your mods are simply what you have listed in your profile, you definitely don't have to rewire it. The stock wiring may not be ideal, and you won't get the most out of that pump, but on a basic 16g setup, on pump gas, that wouldn't be an issue. You will still have plenty of fuel.

Just as an FYI, I was running 25psi on a bolt-on 50 trim setup, on E85, with a NON-rewired 255hp. I now run a BW S362 setup. My fuel pump setup is two 255hp's in parallel, NON-rewired, on E85. Last year I had no issues at 30psi. This year plan on pushing it closer to 35psi.

As has been said, there are definite advantages to rewiring it. I've rewired the pumps on all my past DSM's. Now on this one, for me it was a matter of not adding anything that does not NEED to be added, and keeping with the KISS motto (Keep It Simple Stupid). I had, and currently have, a pump setup that exceeds my requirements, even with the stock wiring. So to keep things simple, I still run the factory wiring. And will continue to do so, until I run into an issue on my car because of it.

To each their own. Good luck with your project.

 

[turboglenn]

Steve and me612 made some very good points but i figure i'll throw my 2 cents in the kitty as well.

The easiest way to put it is like this. You don't have to rewire it, but when you start running lean after a couple little mods and can't get it right no matter how much pulsewidth you throw at it, then you know it's time to re-wire the pump. When i put my cams in my single 255 wasn't rewired and i ran into this. So i rewired the pump and BAM! i had fuel back and was running in the 10's for AFRs everywhere else in the upper boost because the pump just wasn't flowing on the stock tiny little wires. Getting a large voltage feed to the pump does wonders for it's flow. SO if you're not making much HP you might never notice it not being re-wired. But, like i said when you think you're out of fuel when tuning, rewire that pump and watch how much fuel you get back out of it, you will be pleased to say the least.

Now i'm running 2 x 255hp pumps both sharing the same 10 guage feed. Its fine for now but i've had a few people mention that i may even need to wire them up seperately or go larger on the single battery feed wire. I'm a little over obsesive on the fueling now, i got carried away and when i built the dual pump hangar and made another single pump hangar i took and drilled the stock lines out, replaced them with larger diameter line and TIG'ed it all together so now ihave enlarged the fuel system completely from the pumps outlet to the rail and now i finally think i have enough fuel

 

[spectr019]

Even though my motor is fully built, my plans for my 1g are not too aggressive. Don't get me wrong, I will get up on it every once in a while. I guess it couldn hurt.

Galant Greg, you would go through the time and money to fully build your motor, but you won't go through $15 and less than 30 minutes to fully optimize how your fully built motor would run? I'm hoping you didn't try to compromise like this when building your motor...but yeah man get it done, it's just that simple. Plus you just get a good feeling seeing a huge red (if you get the pre-made kit) wire running through your cabin. You know it's feeding some power!!

Also, you WILL hear the pitch of the pump's electrical 'hum' change when you do things, i.e. turn signal, wipers, etc... after you re-wire, so don't worry thinking that something went wrong.

Ben

 

[me612]

Galant Greg, you would go through the time and money to fully build your motor, but you won't go through $15 and less than 30 minutes to fully optimize how your fully built motor would run? I'm hoping you didn't try to compromise like this when building your motor...but yeah man get it done, it's just that simple.

If you only need X amount of fuel for your setup, and the pump flows well in excess of that amount on the stock wiring, how has his setup been compromised?

There are definite advantages to rewiring a pump, but look at his setup and tell me how he is going to endure fuel pump related issues with that pump on stock wiring. If I did not have issues with the same fuel pump setup on a 50 trim setup at 25psi running E85, what negetive impacts do you forsee him encoutering on the same fuel pump setup on a 16G running pump gas?

And again, I'm not debating the fact that rewiring has it's advantages as it is common knowledge that there are advantages. But on HIS setup, I see no issue with leaving it on the stock wiring. He can always perform the rewire in the future if/when it does become neccessary.

 

[spectr019]

the answer has already been given to him - NO you do NOT HAVE AN URGENT NECESSITY to re-wire your 255lph. MY PERSONAL OPINION and point is if you have the resources to do so and it's so inexpensive, why NOT? Plus, that dinky wire to the pump is just like ANY OTHER PART our community of tuners would change in our cars to MAKE IT BETTER. If I PERSONALLY were to be running in mid to high twenty psi, any advantage I could get to insure that my engine had enough fuel (kinda important) I would take. But again, that's PERSONALLY. We all know that our cars are individually different, and I know that with my luck if I were to try something other say worked for them, I'd blow something up. But there ya go, my .02 Sorry that I offended yall who thought that my opinion was too unreasonable.

Ben

 

[me612]

Your reading too deep into things if you think I was offended. Relax. No one is trying to attack anyone.

It's my opinion. Everyone has their own. I just don't see the need to rewire his pump at his level. What good is pumping more fuel at his level. It'll just end up going right out the return line and back into the tank at this point.

 

[pmanaresi]

everyone has been saying that larger guage wire allows more voltage to be carried to the fuel pump which increases fuel volume. this is incorrect. Larger guage wire allows more current to flow. this is also why a separate (higher current) relay is needed.