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Injector(s) hung open, fuel leak on the feed or return lines or a defective pump. If the injectors are hanging open you'd probably have hydrolock on the engine though. I ran into this issue on a 4.3 and found one of the fuel lines on the spider injector assembly had come off and was sending fuel straight into the intake runner for No.1. I was worried my son had trashed the engine when I couldn't get it to turn over by hand but when I pulled the No.1 plug I quickly found my problem.
Injector(s) hung open, fuel leak on the feed or return lines or a defective pump. If the injectors are hanging open you'd probably have hydrolock on the engine though. I ran into this issue on a 4.3 and found one of the fuel lines on the spider injector assembly had come off and was sending fuel straight into the intake runner for No.1. I was worried my son had trashed the engine when I couldn't get it to turn over by hand but when I pulled the No.1 plug I quickly found my problem.
So, when I turn the key to the ON position, what should the pressure read?
just a few days ago, right after I filled the tank up with fresh e85, I lost all fuel pressure. After pounding on top of the sending unit, the car started up and had fuel pressure. A 1/4 mile down the road, lost all fuel pressure again. Had it towed back to my house. Now it starts up but I don't trust driving it.
I hate to start throwing parts at it to fix it but I'm not sure what else to do, or how else to check it.
#1 Remove the supply fuel line off the rail and hook up your gauge directly to it. this will test the check valve on your pump, the regulator and return line.
#2 matter of fact before you do that, with everything still together, remove and cap off your return line and turn the key. This will test to see if your fuel regulator is leaking, send it back to the tank. Hopefully it will hold, which means replace the regulator. If it still drains than do # 1.
You should have 58-60 psi on the fuel rail when you power on the key and during engine operation. Being that there's a pressure drop you certainly need to consider the regulator as the culprit, a defective fuel pump or leaking injectors which could be causing the drop in pressure.
I don't smell any fuel.
The regulator is a Hyperfuel. I spoke to there customer service guy and he said that it was normal for the pressure to bleed off. I posted this question on the boosted LSX Facebook group and here was the reply that I got. Click on the images.
What pump?
Does it have a check valve?
In tank leak?
Verify the condition of the electrical connections.
I have dual Walbro 255s. I've read that they have a check valve.
There are a few electrical connections I need check out.
just weird how I would lose all fuel pressure and then after pounding on top of the sending unit I got my fuel pressure back.
I have dual Walbro 255s. I've read that they have a check valve.
There are a few electrical connections I need check out. just weird how I would lose all fuel pressure and then after pounding on top of the sending unit I got my fuel pressure back.
It's not weird at all. I've got many of vehicle started that way to get it home or to a shop. That's also how the "tow truck" fixes a lot of cars.
It's not weird at all. I've got many of vehicle started that way to get it home or to a shop. That's also how the "tow truck" fixes a lot of cars.
From your experiences, if you had to pound on the tank or the fuel pump itself to get the pump working, id assume the pump was going bad? but Im not 100% on that.
What were your findings?
From your experiences, if you had to pound on the tank or the fuel pump itself to get the pump working, id assume the pump was going bad? but Im not 100% on that.
What were your findings?
yes it's the pump. Normally it's a bad spot on the commentator in the pump not allowing the brushes not to make a good connection. Beating on it, it moves a little bit, makes connection and runs fine until it stops on a bad spot. Its the same thing when you beat on a starter to get it to engage.
yes it's the pump. Normally it's a bad spot on the commentator in the pump not allowing the brushes not to make a good connection. Beating on it, it moves a little bit, makes connection and runs fine until it stops on a bad spot. Its the same thing when you beat on a starter to get it to engage.
Excellent info. I never knew that's what was actually happening to the pump.
Even though the car has been starting up and driving fine, I will replace the pumps anyways.
I bought these pumps from Amazon. Supposed to be genuine Walbros. Both are less than 2 years old.
If you can recommend a more reliable pump, is appreciate it. Thanks
From: Halfway back on the Highway to Hell...again!
I just got a new pump from Quantum fuel and it's a beautiful piece. Lifetime warranty and awesome prices. It's a 340lph and it pushes the fuel very well.
You should have 58-60 psi on the fuel rail when you power on the key and during engine operation. Being that there's a pressure drop you certainly need to consider the regulator as the culprit, a defective fuel pump or leaking injectors which could be causing the drop in pressure.
should f body hold fuel pressure after sitting all night long, after I turn off my 2001 Camaro the psi is around 52psi and holds that for 3-4 hours then drops to like 30 psi then next morning its 0. I just Installed a quantum 340lph complete fuel pump, new filter etc, took off fuel rail with injectors primed the fuel and no leaks..
I just got a new pump from Quantum fuel and it's a beautiful piece. Lifetime warranty and awesome prices. It's a 340lph and it pushes the fuel very well.
'
did you install the full complete fuel pump, do you know what the fuel pressure is when running ? I just installed the same pump and when car running I'm getting 68-70 psi then under boost goes to 58-60 psi, when I just car off fuel pressure is 50ish and stays there for a few hours then by morning its at 0 psi is this normal ? I changed fuel filter and took rails off with injectors to see if their leaking and they are not>
should f body hold fuel pressure after sitting all night long, after I turn off my 2001 Camaro the psi is around 52psi and holds that for 3-4 hours then drops to like 30 psi then next morning its 0. I just Installed a quantum 340lph complete fuel pump, new filter etc, took off fuel rail with injectors primed the fuel and no leaks..
then is it normal by next day sitting over night to be at o psi ? I’m getting so confused some day it should hold some psi for days and some days if it doesn’t bleed off super quick and doesn’t have hard starts then it’s fine .. 😐
It doesn't have to hold ANY pressure while off, as long as it pressures up when the key is on.
Originally Posted by Ssmason
should f body hold fuel pressure after sitting all night long, after I turn off my 2001 Camaro the psi is around 52psi and holds that for 3-4 hours then drops to like 30 psi then next morning its 0. I just Installed a quantum 340lph complete fuel pump, new filter etc, took off fuel rail with injectors primed the fuel and no leaks..
I have a 450 Walbro in the tank and when keyed on the fuel pressure will be 58+PSI and you should not have 58PSI of pressure the entire time once the engine has shut off, it should gradually fall and return to zero. I have a fuel pressure gauge on the fuel rail and I've seen the gauge reach 60PSI while the car has been sitting all day. This is due to the temperature rising throughout the day and as the evening comes the pressure gradually returns to zero.
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Fuel pressure bleeding off. Video inside 
