Fuel Pump Mods

**Sarge** · 04-10-2006, 03:33 AM

Without wandering into the various methodologies and "fixes"....thought I'd share some of my experiance and conclusions.
Firstly the stock fuel setup is gonna crap the bed around 400RWHP....H/C w Nitrous LS1 I had saw a 20lb drop at WOT w/100shot...from 60-40lbs....
I have a FP guage next to the AEM A/F guage so I watch them....
I read all the discussions till my eyeballs fell out.....and when we dropped the 402 in knew we had to do "something" prior to the ProCharger....so we did the bucket mod and Walbro 255...but there is more....after the bucket mod w/new pump we still saw a drop in FP of about 15-20lbs.....so back out came the tank.....the bucket sits flush on the bottom of the tank....we had drilled the holes in the bottom like I had read.....wrong....we drilled additional holes in the side....now we had fuel in the bucket....

Look at this kinked up rinky ass dinky fuel line coming out of the tank from the factory.......think mebbe this could be a restriction?

I did...we replaced it with a more suitable solution....

Put the tank back in....voila! 62lbs FP presure throughout the RPM range....rock solid....now the hog injectors and fuel rails get all they want and the FP doesn't flinch.....there now it works....

So replace that POS hose...drill the holes in the side of the bucket....and for a couple of hundred bucks for the pump and the hose....you got the fuel pressure issue solved....

**tomf301** · 06-11-2006, 06:41 PM

Awesome tip Sarge!

**sic2001** · 03-10-2008, 12:57 AM

did the drop in pressure cause detonation at WOT?

**superchargedblackgto** · 03-10-2008, 03:50 PM

Originally Posted by Sarge

Without wandering into the various methodologies and "fixes"....thought I'd share some of my experiance and conclusions.
Firstly the stock fuel setup is gonna crap the bed around 400RWHP....H/C w Nitrous LS1 I had saw a 20lb drop at WOT w/100shot...from 60-40lbs....
I have a FP guage next to the AEM A/F guage so I watch them....
I read all the discussions till my eyeballs fell out.....and when we dropped the 402 in knew we had to do "something" prior to the ProCharger....so we did the bucket mod and Walbro 255...but there is more....after the bucket mod w/new pump we still saw a drop in FP of about 15-20lbs.....so back out came the tank.....the bucket sits flush on the bottom of the tank....we had drilled the holes in the bottom like I had read.....wrong....we drilled additional holes in the side....now we had fuel in the bucket....

Look at this kinked up rinky ass dinky fuel line coming out of the tank from the factory.......think mebbe this could be a restriction?

I did...we replaced it with a more suitable solution....

Put the tank back in....voila! 62lbs FP presure throughout the RPM range....rock solid....now the hog injectors and fuel rails get all they want and the FP doesn't flinch.....there now it works....

So replace that POS hose...drill the holes in the side of the bucket....and for a couple of hundred bucks for the pump and the hose....you got the fuel pressure issue solved....

I did this same mod...running 10psi of boost, I see a drop in pressure, this is a good fix for N/A, and boost 10 and less, or about 480rwhp and that is pushing it. however if you go more, you will need to put in 2 pumps, external regulator, and upgrade the fuel system......But it works great for above application...remember guys F/I cars require more fuel than N/A..
Great tip Sarge
Brad

**GottaHaveLS1** · 10-02-2008, 08:03 AM

i've been having fuel problems with my bolt on 99 T/A. i've replaced the pump and fuel filter. My lines are slightly kinked so maybe i should replace them. Could screwing the holes out the side help me too?? sorry about bringing back such an old thread

**Sarge** · 10-03-2008, 04:55 AM

Well flow is critical to maintaining fuel pressure...you have restrictions in the fuel bucket yes it is an issue for sure....the "drill mod" definetly works....just don't let the fuel level get below like a 1/8 of tank....

**GottaHaveLS1** · 10-03-2008, 06:28 AM

Originally Posted by Sarge

Well flow is critical to maintaining fuel pressure...you have restrictions in the fuel bucket yes it is an issue for sure....the "drill mod" definetly works....just don't let the fuel level get below like a 1/8 of tank....

but i've had the same bucket in there since i bought the car over three years ago. Is it an issue now just cuz of my new walbro 255 pump? I wonder if it will fix my problem entirely. So does the car just die when i go below that mark?

**Sarge** · 10-03-2008, 08:29 AM

What happens is the new pump will pump the gas out of the bucket quicker than the fuel can flow back in it....so your good for say a 10-15 seconds WOT run then you go instantly lean/kaboom.....or run the very high risk of it....

**shady milkman** · 10-03-2008, 08:33 AM

i know when i go for a new pump etc..i will do the drill mod and change that hose... so i can be ready when the time comes

**GottaHaveLS1** · 10-03-2008, 09:33 AM

it looks like i'll have to do this mod then.

**Sarge** · 10-03-2008, 10:19 AM

I see the same thread in the General...the FBody guys and us have slightly different setups guys.....

rednari · 10-06-2008, 08:23 PM

It is a good write up. I remember when he first posted it. I would add though, from experience learned since Sarge first experimented with bucket upgrades, it is better practice to drill the extra holes in the bottom and not the sides. This way when the tank in below 1/4, and you are corning hard, the motor is less likely to fuel starve.

Originally, I drilled holes in the side too. But later had to go back in and wire some gas tank foam over the holes to stop backflow. I do not know for sure if bottom drilling the holes is a cure all, but I suspect it would help.

Anyway, the holes plus the Waldbro 255 pump will give you enough fuel for almost any type of motor. There are people who have spent many hours and dollars upgrading to the 8 liter fuel module (Silverado module) because it has two inlets, when all you need are two extra holes in the bottom and/or fuel tank foam to stop starvation.

**Sarge** · 10-07-2008, 03:21 AM

LOL...yeah I followed some of the more complex fuel system "upgrades" for our GTO's on another forum for awhile. Unreal! I keep 62lbs of FP at the rails even at WOT....cannot imagine any motor needing more than this bucket mod.

rednari · 10-07-2008, 10:29 AM

Agreed! 62#s at WOT on a 408 stroker is enough fuel for any street car.

**Shagman** · 11-27-2008, 04:55 PM

In need of the fuel line from tank Both the clips broken Any idea (hose was kinked also)
Pontiac has to order from down under Got a love it

Drilling holes as I type APS system air ratio dropping to 10 to 1 above 5 grand and fuel pressure drop

Thanks for any info
Shagman

**scubamark3995** · 06-22-2009, 07:35 AM

Hey Sarge.
I am putting a ls1 in a datsun 280z with about 520 hp,trick flow heads 11.1 comp. , 232/236 .585 lsa 112, fast 92mm intake and throttle body and custom headers. Will be using a RCI 16 gallon fuel cell. Would like to put the pump in the tank to keep it away from the heat. What do you recomend for a fuel system and what size headers(custom made)?
Mark

**GTO1_OHIO** · 06-22-2009, 08:00 AM

I have to totally disagree on one item. It is NOT a good idea to drill holes in the bottom. With a low amount of fuel in the tank, as the gas sloshes around, the bucket will empty out of these hole and you will starve. I have seen several top performance shops say don't do this. LPE is one. The guys that tune my car is another.

**Sarge** · 06-22-2009, 10:07 AM

Originally Posted by scubamark3995

Hey Sarge.
I am putting a ls1 in a datsun 280z with about 520 hp,trick flow heads 11.1 comp. , 232/236 .585 lsa 112, fast 92mm intake and throttle body and custom headers. Will be using a RCI 16 gallon fuel cell. Would like to put the pump in the tank to keep it away from the heat. What do you recomend for a fuel system and what size headers(custom made)?
Mark

Walbro 255......more than enough...I assume your going returnless?
1 7/8" on the headers with those numbers/heads/compression ratio.

**Sarge** · 06-22-2009, 10:09 AM

Originally Posted by GTO1_OHIO

I have to totally disagree on one item. It is NOT a good idea to drill holes in the bottom. With a low amount of fuel in the tank, as the gas sloshes around, the bucket will empty out of these hole and you will starve. I have seen several top performance shops say don't do this. LPE is one. The guys that tune my car is another.

Yeah and dont sit too close to the TV cuz you'll go blind. Totally overblown internet bullshit. I have ran mine down to damn near nothing with no issues at all many times. I am forgetful....but I do try and not let it go below a 1/4 tank....run em at the track at 3/8 full and your golden....and knock that shit off in the shower...you'll grow hair on your palms.