[Chicagoareabmx]

I'm currently trying to set up a drop-in ready fuel sending unit with pump.

Currently on the stock LT1 - stock cam, heads, etc, with the bolt ons - cold air intake, full 2.5" exhaust with long tube headers, but the car sees a lot of extended high rpm use on the road course AND will eventually be refreshed to LE heads/cam road race style build - aiming for the 350-400whp mark.

Looks like 400ish whp is the mark where a lot of folks talk about upgrading the fuel system?

Curious to hear thoughts or links to threads where this has been discussed with currently available pumps.

Thanks!

 

[Sshockr]

I'm just over 400rwhp on a factory style Walbro 255. Important part as the Racetronix style upgrade for the power wire feeding the pump from the fuse block.

-Brian

 

[sherlock9c1]

At one point I did some calculating and the stock pump was around 125 lph, if I remember correctly. I just tried searching on ISSF and didn't find it. You can pretty easily calculate how much fuel you need based on a BSFC of 0.35. I just remember being shocked at how much overkill the 255 pump everybody loves to "upgrade" their relatively stock cars with, given that we have a return-style fuel system; overpumping just heats the fuel up.

If I could build my own fuel system, I'd use a return-less variable pressure fuel system with PWM and variable voltage control on the fuel pump, allowing the injectors enough dynamic range to fuel reliably down to 400rpm and then all the way out to redline at max airflow. But.. that's not how these cars were setup. So I upgrade the wiring to the stock pump on my relatively stock cars and call it good.

 

[Sshockr]

Yes it's probably overkill. Part of me bought into the hype, but it's reported reliability is better than the parts store brands available and I wasn't putting my 270k factory back to use on a brand new engine and risk it dying during break-in and wrecking something else.

-Brian

 

[Dandy]

I'm just over 400rwhp on a factory style Walbro 255. Important part as the Racetronix style upgrade for the power wire feeding the pump from the fuse block.

-Brian

Brian,
I am not at a point of needing to upgrade or replace my fuel pump. Do you know if there is a wiring upgrade kit for the factory pump. Assuming my car still has a factory pump, no telling what previous owners may have done. If so do you know if upgrading the harness to the existing pump may help extend the life? I have no desire to drop the fuel tank if I don’t need to for a pump replacement.
-Dan

 

[Sshockr]

Dan, lots of people like the kit from Racetronix. I was re-wiring alot of my engine harness anyway as part of my swap to the LS computer so kinda did my own mods using an additional relay and spliced in the trigger at the fuse box. The Racetronix kit is plug and play. I haven't looked in a while but Innovative Wiring is the other place I would Google to see if he has a plug and play kit. I have their headlight and battery harness upgrades in my car.

-Brian

 

[95wagon]

Some random musings here.
Remember pump ratings are typically at pump, no pressure, optimal voltage.
Horsepower used in calculations is non power adder crankshaft HP

That said the only stock GM pump info I have personally is
330 rwhp , stock pump at 10 volts would not lean out . LIKELY no leeway though.

Yes a variable output PWM pump with no return would be the end all, with some caveats

Thing about non return systems ( yes every fi street car I own has one)
Any gulp, burp, bubble ,the only way out is though an injector.
Any hot soak of the rails that causes vapor, that vapor has to go out the injector.
If you built a PWM returnless system that was variable presure and ran super low pressure at idle and low load you might be inviting boiling fuel in the rails.
My LS7 is returnless, 58 psi.
It in a narrow band of outside temp,engine temp, time parked, will be soggy for a couple seconds on restart.
It uses a Kinsler high flow flapper door style, check valve and does not hold pressure for ever.
I surmize it is "eating"fuel vapor.
If designing from scratch with a PWM pump controlling pressure, I would be tempted to keep the pressure up to reduce possibly of vaporising fuel and better atomisation from nozzles.
Also a return regulator off the rails set at a higher pressure than set in the pump.
This for two reasons.
You could set the pump to run full blast on key on, this to purge hot fuel and any air on start up.
Also as a fail safe if the pump had a runaway.
Just my thoughts.

 

[95wagon]

To add , in my case , my walbro 255 runs at zero pressue,so it,pumps at about 200-210 liters per hour.
My "044" at 58 psi is about 210 liters per hour
This more or less falls into the 600 ish hp range I am likely in.

 

[Fix Until Broke]

Does anyone know what the current draw is on the factory pump?

 

[95wagon]

Stick your multimeter probes in the fuse box ?

 

[Fix Until Broke]

I would but my multimeter has been MIA for a few months and I haven't talked myself into spending the money to replace it.

 

[95wagon]

In the name of science.

Stock regulator no reference, so 47 psi ish.
I did use meth , no need to burn the garage down to answer a question.
I tried my fluke first but was seeing a voltage drop as it is only rated to 10amps so I brought out the cheapo inductive, which has shown to be quite accurate.

 

[Z09B4U]

Stick your multimeter probes in the fuse box ?

30Amp Amp meter for fuses. Weirdly enough I was testing a fuel pump with it last.

All my other meters max out at 10Amps.

 

[Fix Until Broke]

Awesome - Thanks for doing that. Seven amps is more than I would have thought! Guess that explains why the wiring is so important on these. If someone upgrades to a higher flow pump, I'm guessing it will draw more current (assuming same fuel pressure and same pump efficiency) which would make the wiring even more critical.

 

[95wagon]

30Amp Amp meter for fuses. Weirdly enough I was testing a fuel pump with it last.
View attachment 197663

All my other meters max out at 10Amps.

Yeah, so your point is ?
Rather than me cobble up a test, you could have walked out to your car ?

 

[Z09B4U]

Yeah, so your point is ?

It was not to offend you.

I thought for normal diagnostics you had the right suggestion.
I thought someone came up with a easy to use diagnostic tool to use. I do not use it often but I think it is great to have.
Something like a pump motor will draw a lot on startup and could blow a normal 10 Amp meter fuse($$$$) even when the motor normally runs on less current.

Rather than me cobble up a test, you could have walked out to your car ?

It is in storage for the winter. Telling anyone here a crown vic pump draws 5 Amps would be useless. (My last use) But it is a good test if you think your pump is bad.
The fuse box normally is the easiest test point, but for the b body not correct as the same fuse feeds two battery feeds to the PCM which could change the result..
Removing the relay and use the amp meter there would work or the red prime wire.

Seven amps is more than I would have thought!

This is one of the few times GM used the correct wire. 14ga(2mm) over 25 feet should not have much loss.
My memory of pump current draw was around 5 Amp at 12 Volts at the bumper connector C402 but it has been several years since I tested it.

If someone upgrades to a higher flow pump, I'm guessing it will draw more current (assuming same fuel pressure and same pump efficiency) which would make the wiring even more critical.

Z09b4u, aeromotive said to use a 25 amp fuse, but the pump rating is a MAX of 20 amps. The amperage draw is a curve based on fuel pressure, and 20amps is at a pressure that I likely will never see with a 55-60ish base fuel pressure and a 1:1 rise with each # of boost (max boost this blower could ever make would be less than 20). Even at 20psi, fuel pressure would be 80psi max, and Aeromotive’s chart shows that to be about 17amps at 13.5volts. That would only be intermittent as well, and the vast majority of the time it would be well below that. So it seems like with 10AWG and the metripack 280’s I’d be plenty safe. I’ll take your advice and go with a 40 amp relay.

If one is making horse power and needing a large pump current will be higher.

One part of the wiring is already critical on the sedan. The fuel pump shares it's ground with ALL the lights on the back of the car. The pump needs it's own ground wire.The wagon splits the lights into two separate ground points and I have not looked at the loads on the wagon grounds.

If the replacement pump draws more that 7 Amps the pump wire needs to be resized and the wire will get big quickly due to the distance.

 

[SSandman]

Lots of good info in here

I'm currently trying to set up a drop-in ready fuel sending unit with pump.

Currently on the stock LT1 - stock cam, heads, etc, with the bolt ons - cold air intake, full 2.5" exhaust with long tube headers, but the car sees a lot of extended high rpm use on the road course AND will eventually be refreshed to LE heads/cam road race style build - aiming for the 350-400whp mark.

Looks like 400ish whp is the mark where a lot of folks talk about upgrading the fuel system?

Curious to hear thoughts or links to threads where this has been discussed with currently available pumps.

Thanks!

FWIW I think you'd be fine with a Walbro 255 with pretty much any N/A Lt1 setup you could dream up except for the most extreme setups. At 400whp I think you'd be fine, but if you wanted a bit more wiggle room you could look into an Aeromotive Stealth 340 pump. Pretty sure you could make one work either drop in or with very little modification to the bucket/hanger. Knowing with how you push your car and the type of racing you do, I would upgrade the pump and harness regardless of whether or not the stock pump could handle the power levels. Reason I say this is because your car probably spends a significantly higher amount of time at higher RPM's than the average street/strip car and the pump is seeing higher pressure/load more frequently and for longer sustained periods of time. I'd rather be ripping around a track with a walbro 255 working only half as hard as it could be than having a stock pump going max effort to maintain fuel pressure under load.

With the 255 drawing more amps and the fact that your car sees such frequent race track use with sustained/frequent high RPM's could mean more heat in the harness than the average street car would see running that same setup. Heat, like length, also has an effect on particular wire diameter's ability to handle current. May be overkill, but if it were my car running say a 400-450whp N/A stroker being frequently raced, I'd do the following.

Walbro 255
10 gauge power
10 gauge chassis ground
Stock fuel lines should be fine.
Regulator of your choice

I doubt you really need 10 gauge, but can't hurt to upsize.

Only other thing I'd think about is fuel control, but if you aren't having any starvation issues now out on the track I assume you only run it with a decent amount of fuel in the tank? Wouldn't want to be leaning your new motor out.

 

[SSandman]

I THINK the racetronix plug and play harness kit uses 10 gauge wire from what I remember installing it on another B body I had but I never actually measured it. It would probably be the easiest way of doing it.

 

[Marky Dissod]

If our fuel pump is the same as the LT4 fuel pump when / where it matters, it should be able to handle 345-360 horsepower @ 43psi with little concern.
Wiring upgrades on our cars are seldom a bad idea.
(eats popcorn in hopes of learning more …)

 

[95wagon]

More trivia.

LT1 pump , free flow with about a foot of 3/8 hose , 4.52 amps
Peak amps on start up with no pressure head 4.64 amps
Again methanol, not gasoline
PCM current draw at rest, both batt and ign circuit 0.47 amps

96 lt4 295-305 ish at the wheels