Recently I was havign a problem with my fuel pump, My psi was dropping when i started to build boost. I recently purchased a racetronix fuel pump, after install when i started the car, I am getting 60 psi at idle but as soon as i start to make any boost the fuel psi drops, any ideas why this could be or what i need to fix it.
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
If your on stock rails with the intank fpr then thats your problem. Your going to need a boost referance fpr to have steady fuel psi. Then again u may be out of pump. A single 255 and hot wire will only net u 500+ hp even with the 60# injectors
__________________ 760 HP 689 TQ !!! THANKS LETHAL PERFORMANCE!!!
14psi
Recently I was havign a problem with my fuel pump, My psi was dropping when i started to build boost. I recently purchased a racetronix fuel pump, after install when i started the car, I am getting 60 psi at idle but as soon as i start to make any boost the fuel psi drops, any ideas why this could be or what i need to fix it.
Justin
F99 returnless rail systems will experience pressure drop. This is because the point of regulation is at the back of the car in the tank. The location of the fuel pressure regulator (FPR) does not allow it compensate for line pressure drop even though the pressure is stable at the back (regulator location). There are two options to get around this problem. First is to convert the system to a rail mounted FRP return type (best). The second option is to install a pump booster which is activated at the point where rail pressure starts to drop. The boost in fuel volume overwhelms the regulator / return line thereby increasing the fuel pressure at the back of the car which translates to higher pressure at the rail. We recommend the MSD unit for FI applications as it ramps the voltage based on manifold pressure. This prevents a short but abrupt fuel pressure spike which causes the motor to hiccup from brief over-fueling. If you are using an instant-on N2O system then the KB BAP can be considered as well. Please understand that this is not an issue with the Racetronix system but rather a design limitation of the factory configuration. Nominal operating pressure should be between 58-62PSI. Idle pressure may drop slightly as the fuel system warms up. Under WOT fuel pressure may gradually drop as low as 52PSI. If your fuel pressure drops off more drastically then you may require the FPR relocation and / or the booster. With F99 FI cars typical RWHP support is 500-550RWHP. Adding a pump booster and a FM FPR can extend this support 50-100HP more depending on your motor's BSFC. If you require more HP support than this kit can handle there is the option of a dual in-tank system which is plug and play as well. The DP system can support over 1000 HP with a FM FPR system.
Here's my confusion, the pump that was in it before I went with the racetronix wasn't a stock pump, it was a walbro. It was on the car when i bought it, the fuel pressure didn't drop near as much on that pump as it does now. It didn't utilize the venturi system, though, not sure if that makes a difference. Why would it drop more with the new pump?
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
Here's my confusion, the pump that was in it before I went with the racetronix wasn't a stock pump, it was a walbro. It was on the car when i bought it, the fuel pressure didn't drop near as much on that pump as it does now. It didn't utilize the venturi system, though, not sure if that makes a difference. Why would it drop more with the new pump?
Justin
If there was a stock Walbro in the bucket, the bucket would have to had been modified for it to work properly. The Racetronix fuel pump will not work properly if the bucket is modified in any fashion. Modification of the bucket may also cause damage to the Racetronix pump.
The Racetronix pump diverts a small amount of its fuel output to support the jet-pump.
ya, the old bucket was modified, had the venturi jet removed from the buttom, I had to buy a whole new bucket. So the reason the pressure is dropping more is because of the venturi system? I will take the car out tomorrow and see how much the pressure drops when i drive it, I am hoping it doesn't drop below 50.
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
ya, the old bucket was modified, had the venturi jet removed from the buttom, I had to buy a whole new bucket. So the reason the pressure is dropping more is because of the venturi system? I will take the car out tomorrow and see how much the pressure drops when i drive it, I am hoping it doesn't drop below 50.
Justin
Either way it sounds like you are on the edge so some upgrades may be in order.
I took the car out today and got on it, the pressure dropped to 50 at full boost, which is 11 psi and didn't go below that. I have the racetronix pump with the upgraded wire kit you guys sell. Is it ok as long as it doesn't drop below 50?
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
I took the car out today and got on it, the pressure dropped to 50 at full boost, which is 11 psi and didn't go below that. I have the racetronix pump with the upgraded wire kit you guys sell. Is it ok as long as it doesn't drop below 50?
Justin
You are on the edge so you might have issues if your battery voltage drops or it is a very hot day. The drop in fuel pressure is mostly due to the location of your regulator at this point.
k, took the car to get tuned by NicD and made 524 to the wheels and the fuel psi didn't go below 50, so I am pleased with the racetronix pump. Thanks for your help
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
k, took the car to get tuned by NicD and made 524 to the wheels and the fuel psi didn't go below 50, so I am pleased with the racetronix pump. Thanks for your help
Justin
I'm doing the same thing today..... Deciding weather i should replace the "bucket" where the walbro had to be modified. Did you replace the bucket? Did you notice a difference? What did you do to the venturi before you replaced the bucket with a new one?
__________________ 02' T/A convertable,ram air,TH400,3500 stall,trans brake,moser rear w/4.10's,tubeler upper & lower A-arms,QA1 raceing shocks,drive shaft loops,subframe connecters,OK to much to list. PROCHARGED F1C & 451 LSX IN THE WORKS!
So my fuel pressure sits around 55 now, and it used to sit at 60 when daily driving, and I got on it today and the fuel pressure dropped below 50 at WOT and the car felt a lttle weak. This is the first time this has ever happened, and I installed the racetronix fuel pump a half year ago and got the whole wiring harness with it. I know that I am on the edge of needing to upgrade my fuel further, but I wasn't havin problems with the pump until now. Is there something that could be affecting this? voltage? bad ground?
Please help
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
so i changed my fuel filter and it was filthy, but my psi is still low and this is a problem that has been getting worse. I have the racetronix hotwire kit and i still have the stock wiring near by, I have switched between both and the psi is a little higher with the racetronix wire. is there something else I can be checking to determine why my psi is low
thanx
justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
__________________ 2005 white diamonds Escalade EXT,LT's w/ ORY,Shaner ported TB,MSD wires,JBA catback,CAI w/ Green filter,160 stat,SCT tuning by Henson,free mods,and more bass than a crack house!!!
Stroker and l92 top end to come!
Last edited by MeentSS02; 09-15-2009 at 08:23 PM..
Just posting a conclusion to my problem. I spoke with Lonnie about my problem with my pump on the phone. We narrowed it down to a few possible issues. I had a spare fuel bucket at the house and swapped out my fuel pressure regulator that was in the top of the fuel bucket assembly, and that fixed the problem. My fuel pressure was at 55 psi at idle and now it sits at 62 at idle. I couldn't be happier, b/c I was on the verge of turning the car over to a local garage to pay them to fix the problem. There have been several problems that i have had with my car and the awesome people on this forum have once again saved me hundreds of dollars by helping me diagnose and fix the problem on my own. THANKS AGAIN!
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
There are many possible issues in a fuel system that are often blamed on the pumps. Atleast you solved the problem without throwing any more money into it.
Not sure if you had something contaminating the regulator, but for all reading this, it is imperative to keep the lines clean as a small speck of dirt can cause the regulator to malfunction, causing the problems listed above.
Unfortunately the solution to my problem was only temporary, the next day my fuel pressure was back down to 55. My next question is does the fitting on the end of the fuel rail with the wires running to it only send a signal to the fuel pressure gauge, or does it affect the pressure the pump sends?
thanx
Justin
__________________ 99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD
racetronix pump low psi 
99 ss Built 5.3 Liter, bored, Stock Crank, Eagle Rods, Diamond Pistons, Stock 6 Liter Heads and valves. Upgraged push rods & valve springs, .570" Lift cam, LS6 intake, 60 lb Motron Injectors, Tuned with HP tuners, old QMP kit, Precision T-67 Turbo, Built Six Speed, Carbon fiber discs, billet shift forks, Pro 5.0 Shifter, Spec Stage 4 Clutch, Stock 10 bolt w/TA Built Cover and Auburn Differential 524 whp at 11 psi, tuned by NicD 
