Fuel pump can't hang
 

I originally posted this in the fuel forum but it isn't getting any attention. It looks like the combo of increased horsepower and increased ambient heat is taking its toll on my fuel pump. It's a Walbro 255lph for an LT1 with the Racetronix hotwire kit, an adjustable FPR and Ford 30# injectors are down the line. I'm running 4 bar fuel pressure. I just drove the car a few hundred miles over the weekend in 90+ degree heat and my digital fuel pressure gauge showed that pressure was a few psi low. It would dip even lower with more engine load. During a few of my WOT passes on 2 lane highways, the pressure even fell to 3 bar (down around 43 psi). It did the same thing during a drag race weekend. Fuel pressure was falling into the 40's by my 5th race. Once it got later in the day and ambient temp dropped back into the high 70's, the pump would return to 58psi and hold even during WOT. I want to upgrade to a pump that was designed for 4 bar fuel systems and is able to handle 400 rwhp and daily driving in extreme heat. I already browsed ws6store but there are a bunch of options between racetronix, accel, walbro, aeromotive, holley, etc. I'd like to hear what people recommend. Also will a 98-02 pump be a direct fit for my 94? Is the electrical connector the same?

A 255 should be able to handle 400rwhp all day long. Your fuel pressure should be a continuous 43 to 45psi. No more is needed with your setup.

I agree. When the pump is working 100% my pressure gauge doesn't flinch. But when it's piping hot outside, the pump can't maintain 58 psi (I'm running 4 bar now).

I spent some more time browsing ws6store and racetronix. Racetronix has some handy graphs on their site that shows psi vs lph vs amps. Looks like a 255 lph pump running at 60 psi will only push out about 225 lph and a 340 lph pump running at 60 psi will push around 270 lph. I'm leaning towards the 340 so that if it has trouble in the heat like my current 255, I will hopefully still have enough fuel to maintain rail pressure.

Where is this measurement being taken? Is the pump in a fuel pump bucket?

I have an Autometer digital fuel pressure gauge, measurement is taken from the schrader valve. The pump is in the bucket.

Have you tried to bypass the FPR to see what happens?

The thought never crossed my mind. Initially I was hoping it was the pressure gauge getting heat soaked and sending bad info but there is a extremely noticeable tactile difference in the car when the pressure drops. When the pressure dropped into the 40's at WOT the car just had no power. Then at one point I was sitting in a left turn lane and the pressure dropped into the 40's (and the pump whine got REAL loud) and when the light turned green and I tried to get moving it bogged hard. I didn't think to check my wideband at the time.

Do you have a fuel filter maybe clogged and also check the pump wiring, all connections and grounds

Does this only happen when the fuel level is low?

You could always add in a fuel cooler to bandaid things.

I don't think it's the filter or wiring since it works perfectly up to about 85-90 degrees ambient temp.

No, the amount of fuel in the tank hasn't gotten below 7 gallons all summer. If I fill up, the cold gas helps pressure stay at or near 58 psi for a while but the gas warms up eventually. I'll look into fuel coolers.

Usually a mechanical issue. Pump may be going bad or somehow experiencing cavitation.

I'm still having trouble understanding this:
I am not sure why you are running that high of fuel pressure when it's not needed? Perhaps you've overworked the pump and it's dying? What I mean by 43 to 45psi (perfect being 43.5) is at WOT that's all that's needed for an N/A setup.

Its one step closer to LS1-ness which we all know means godliness.

The same walbro 255 is happy running in a LS1 car as it is in an LT1 car, so I would doubt the pressure is causing an issue.

What's stock FP on a LSx?

4 bar

Well I went ahead and bought a Racetronix 255. Today's project was installing it and after a full day of working in the trunk in 95 degree heat, the fuel pump ended up being a dud. Once I got the pump installed and fuel filter replaced, I primed the pump about a dozen times but never got any fuel pressure at the rails. When I tried starting the car, it would just crank and never fire, fuel pressure stayed at zero. I pulled the pump back out to investigate and noticed the outlet hose was bone dry, not a drop leaked out. The flex hose was dry inside as well. I double checked the wiring to make sure I didn't have anything crossed and it was good. Then I threw the old pump back in and got fuel pressure on the first prime. Car starts and runs great. More than a little frustrating to say the least, especially since I'm also dealing with a leak in one of my brand new 11" wide Torque Thrust 2 wheels. Yes, the aluminum wheel has leak under one of the spokes. Anyway, at least the new pump came with a wire harness that has thicker gauge wires so maybe that will help. The old stock power wire looked like the terminal was burned. Also curious, is there a more heavy duty relay I can use instead of the stock relay? Or are all relays the same?

If you run a hotwire kit, it bypasses all the factory wiring for power outside of the tank. You will need to buy an upgraded bulkhead wire kit for tank inwards.

Have you looked into the voltage going to the fuel pump, you may benefit from one of these.......

https://www.jegs.com/webapp/wcs/stor...ear=4294829855

Tried running the new pump and it wouldn't start. My gauge was reading 0 psi no matter how long I cranked the engine. Pulled the pump back out and asked ws6store to exchange it. They asked that I try a bunch of stuff first so I decided to just make a video with a bucket of water proving that it was broken but during filming the electrical jolts brought it to life.


I tried it again a few days later with gasoline and it worked great. I'm still not putting it in my car, I don't trust the thing.

In the mean time I've been using my old Walbro pump with the new thicker in-tank wires that came with this Racetronix pump and it's been working much better. We've had a number of 95 degree days and fuel pressure is rock solid at 58 psi no matter what. I put the car through a real test a few days ago when I took it for a 150 mile loop through the mountain passes of Oregon and fuel pressure didn't budge. Once I got back to town, pressure was dropping to 55 psi at idle at one point so looks like it's not perfect but still much better than before. And with temperatures finally dropping around here I have plenty of time to figure out what I want to do before next summer.

I figure I'll update this thread rather than start a new one. I have since installed a fluid cooler in my return line hoping the cooler gas would prevent my fuel pressure loss. Unfortunately that has not been the case. The fluid cooler thread is here: https://ls1tech.com/forums/lt1-lt4-m...el-cooler.html

This week I installed a Racetronix 340 lph pump and got the same symptoms. Pressure loss after about 30 minutes of driving accompanied by fumes and loud whining from the pump. I've emailed Racetronix about it and haven't heard back. In the meantime I found this post:


I'm desperate for a solution here and figure upgrading the bulkhead wires is worth a try. I'd like to wait for a response from Racetronix before ordering but I emailed them yesterday and heard nothing all day today. They have 2 B-body bulkhead harnesses on their site and a universal bulkhead harness. It looks like the universal harness is my only option. Anyone have experience upgrading their bulkhead harness?

Is the car running lean or having any problems? I don't think I saw anything in your posts about any issues other than fuel pressure.

I remember reading that LS1 cars are supposed to have 58+psi from the factory, but I tried a couple different gauges on my cars and both read about 54psi at idle with the factory fuel pressure regulator. I ended up installing a new Walbro 255lph pump and new fuel filter on one car. After the swap it still had around 54psi. I then ran 8 gauge wire off the battery to a heavy duty relay at the back of the car. I think the relay has 10 gauge wire going into the tank to feed the pump. After all that I still had 54psi. heh..

Chad