Crunch

I searched all the way back to 2002, but I couldn't find a specific answer to my particular problem.
I have the Walboro 340 in-tank pump AND the T-Rex in-line pump, but the fuel pressure now drops to 40PSI at WOT in 3rd, 4th, and 5th gear. The fuel pressure did NOT drop this much when I had the stock in-tank with the T-Rex, ONLY since the Walboro 340. I know that with bigger and better fuel pumps, or in my case TWO strong fuel pumps, the fuel pressure will be lower than a stock setup, but this low?
Black LS1 T/A and Harlan, you guys seemed to know the most in the other posts I searched through. Can you help me with this one, or anybody else?
BTW, on Monday, we are switching over to 50# injectors, hopefully this will help.
Thanks. I appreciate any responses.
Randy.


Correction: Fuel pressure now drops to as low as 20PSI at full throttle over 6000RPMs.

red ws6 99

You did not mention what you were using for a fuel pressure regulator? I hope its not the stock one. The stock one does not do well with the increased volume, plus you would want one that is boost referenced, if you don't already have one.

Gary

1dirtyZ

iTrader: (1)

i had the same problem , i had the intank walbro and the inline aeromotive.

i turned out to be that when i put in the intank unit i didn't tighten the hose coming from the pump to the top of sending unit enough( it has to be on pretty tight). what would happen is that when ever i got on the car the fule pressure would gradually drop .
the best wat to test this is to unplug the power to your t-rex pump and take the car for a spin ( no wot runs just part throttle), if the pressure still drops as it did before then that could be a good indicator you have a leaking hose on the pump.

hope this helps

mike m

iTrader: (6)

yo im having the same problems, i have a t-rex inline, and tried adding the walbro intank pump. i know have worse fuel pressure then before. i even put another fuel pump housing in the tank and it still drops bad. does yours drop sitting in park? just revving the gas? mine goes from 62 to 50 just reving it. It seems if you own a 99 up you need to do a complete fuel system because of the stupid intank fuel pressure regulator. I am looking for a 97 corvette fuel rail, and im gonna use 6cyl fuel lines so i can have an aftermarket fuel pressure regulator on the rail. I just hope we didnt screw up the t-rex by putting a larger pump behind it. looks like im not alone.

red ws6 99

If your pressure is dropping just sitting there at idle with a little blip then its most likely not the pump. The regulator is what controls your pressure to the engine. I would replace that with an external unit.

Gary

mike m

iTrader: (6)

redws699 the problem with a 99 up car is the regulator is in the tank. there is one fuel line. it t's off at the back. so there is no way to put an aftermarket regualtor unless you change the entire fuel system. im just wondering if the intank regualtor doesnt work with the external pumps.

Crunch

I did not perform the installation of the supercharger or any of the fuel components. But I'm pretty sure that a fuel pressure regulator was not in that list. All we put in was the Vortech V9 kit AS IS out of the box, plus the Walboro 340 in-tank pump, heads and cam, and LS1-Edit tuning. I never saw a "fuel pressure regulator" on any list of parts, nor did I order one. I didn't know I needed that!!
What do I do now? Where can I get one and how fast can I get it? Or do I need a whole new fuel system like Mike said? Tom Byrne was running this exact same setup last year, and I don't remember him saying anything about a regulator (but his car WAS a 1998).

I'm lost.

Crunch

Mike, the fuel pressure IS low just sitting at idle. It NEVER reaches 62PSI anymore. It hovers around 58, 56, 58, 60 just in idle. As soon as I drop the hammer, it slowly works its way all the way down to 20PSI. WTF? I just paid all this money for the T-Rex, injectors, and the freakin' Walboro in-tank and labor, and the **** still won't work! The car feels like somebody slammed on the breaks when it gets to 5000RPM, like its choking or something. I just got smoked by a stock corvette C5. WTF?

Black LS1 T/A

This is my experience:
With the In-line pump, idle and cruise fuel pressure is less than stock pressure because the inline is a restriction until it is running. Aeromotive's pump regulator can cure this by letting the pump spin slowly at lower rpms (without heating the fuel unneccesarily with a 2nd pump running at full speed) and turn on full at WOT.

I took the Aeromotive off and put two Walbro's in. I still have the stock regulator.

I have about 59.5 to 60 PSI at Idle and cruise, about 58 or 59 at part-throttle. The D1SC and 422 with 55 PSI injectors sucks it down to about 54 or 55 lbs at the rail at WOT. I have the 2nd Walbro come on with a Hobbs switch and relay that senses when I go to boost.

Hope that helps.

DaveSchott

iTrader: (5)

This is not true, the incon kits were furnished with an rear mount external regulator that left the fuel system stock past the tee. Look in the fueling section for more info.

Crunch

Thanks.
I think your problem was a little different than mine. My fuel pressure drops to 20PSI(??!!!) at full throttle in 3rd, 4th, and 5th gear. I was better off with just the T-Rex and the stock in-tank! At least then it only dropped to 56PSI.

SS00Blue

Stupid question. Are you POSITIVE that the inline is running? Could the walbro install have netted a loose connection on the inline pump? It sounds like a HUGE restriction is afflicting your system.

SC-

Crunch

I'll mention this to my mechanic today. But I'm SURE he'll check this before the next dyno run this week.

red ws6 99

I also have an Incon kit, its actually quite easy to put an external in. The difficult part is getting the right adapters for the plastic quick connects. The return line tees off just after the filter it then goes back in the tank. You remove the intank regulator and put in the new one. Its not as good as putting one at the engine but it works. Also the 98 f-body had the same setup for the regulator. The 97 corvette had the regulator were our pulse damper is.

Gary

Crunch

So...
1. Check the T-Rex inline pump, make SURE its working. And if it is, then..
2. Order the Aeromotive fuel pressure regulator.

I saw in another thread that there were a couple of models. Which one is the best for the 1999-2002 F-bodies? And who sells these?

Crunch

We'll check this too.
Thanks.

Crunch

And the winner is 1dirtyZ!!
Looks like the same exact problem, the hose came loose.
Thank you for your quick responses everyone. Gotta love the folks on LS1Tech.com!

StalkerLS1

Oh Hell yeah!.. that's awesome news!.. Man you had me worried about mine.. I still haven't gotten a FP Gauge after I recently installed a Walbro.

What's your FP holding at now?

2001CamaroGuy

iTrader: (6)

It can be done (I did it on my 01 Z28) without "too much" work. The simple way (how I did it) is to use your EVAP line (the line beside the fuel line) as the return line. Then plug the "return out" on the t-fitting (under the car) and connect the rubber return line from the fuel tank to the evap line. Strap a 97/98 fuel rail on the car and there you have it, a return line system without changing much.

The better way (how I "should" have done it) is to purchase the V6 lines and use them (hard and soft lines). The V6s have the regulator on the engine and as such have three hard lines instead of two.

Chris