5.3 fuel pump

[Bama92]

Goodmorning guys I got another question/problem I need some help with. So I have a 5.3 vortec that stalls when u accelerate. I hooked up a fuel pressure gauge and saw that at idle I have 60psi but when I accelerate it'll drop the pressure dramatically. The harder I accelerate the lower the pressure gets. So what I'm looking for is what type of set up works. (i.e. is your pump in the tank or on the frame rail, what brand works best). Also could I take the original sending unit (from a 91 chevy) and beef up the fuel pump on that unit.

 

[Schurkey]

Goodmorning guys I got another question/problem I need some help with. So I have a 5.3 vortec that stalls when u accelerate. I hooked up a fuel pressure gauge and saw that at idle I have 60psi but when I accelerate it'll drop the pressure dramatically. The harder I accelerate the lower the pressure gets. So what I'm looking for is what type of set up works. (i.e. is your pump in the tank or on the frame rail, what brand works best). Also could I take the original sending unit (from a 91 chevy) and beef up the fuel pump on that unit.

WHAT VEHICLE???

Is the fuel pump getting proper voltage/amperage? Nothing wrong with a properly-functioning in-tank pump--but a pump starving for electrical power isn't going to deliver pressure/volume when the demand goes up.

How old is the existing fuel pump? Fuel filter?

 

[Bama92]

WHAT VEHICLE???

Is the fuel pump getting proper voltage/amperage? Nothing wrong with a properly-functioning in-tank pump--but a pump starving for electrical power isn't going to deliver pressure/volume when the demand goes up.

How old is the existing fuel pump? Fuel filter?

They're less than a yr old. I could see voltage being an issue if it happened all the time but it only happens during WOT or hard acceleration

 

[Schurkey]

I could see voltage being an issue if it happened all the time but it only happens during WOT or hard acceleration

No. Weak electrical system provides enough power to the pump to fully-supply and engine at low power. With increased demand, fuel flow increases and pressure drops.

So you need to verify voltage as close to the pump as practical, preferably while the fuel demand is heavy.

That doesn't mean that the pump can't be wounded, or there's a split hose inside the tank bleeding-off pressure. And it takes ONE tank of contaminated fuel to plug a fuel filter.

You need to verify all this stuff.

 

[badco]

Gmt400s in 96 had issues and recalls due to fuel pump wire being to small for the new vortec engine. So a 91 would still be small wire. Also volume could be a issue but unlikely since a 94 454 holds 30psi on same lines. Most LS like 45psi. Try running a straight 12v on a switch from battery to pump. Also make sure ground good. C3500 I been helping with the ground is black inside even 4" back

 

[Nickpisp]

Goodmorning guys I got another question/problem I need some help with. So I have a 5.3 vortec that stalls when u accelerate. I hooked up a fuel pressure gauge and saw that at idle I have 60psi but when I accelerate it'll drop the pressure dramatically. The harder I accelerate the lower the pressure gets. So what I'm looking for is what type of set up works. (i.e. is your pump in the tank or on the frame rail, what brand works best). Also could I take the original sending unit (from a 91 chevy) and beef up the fuel pump on that unit.

What pump do you have in there now?

 

[Bama92]

What pump do you have in there now?

It's a WALBRO/TI 255LPH UNIVERSAL EXTERNAL INLINE PUMP, GSL392

 

[Bama92]

So I did some digging on the pump and I have 60psi and 12v while it's running, but once it gets hot (around 195-200) that's when the problem starts. The psi will drop under a load but the voltage never will. After driving it around I parked it and left it idling to check something else and heard the fuel pump just quite and the psi dropped to 10 but it still had 12.75 volts going to it but it wasn't running. So whats some other options to try

 

[kennythewelder]

The in tank, 5.7L Vortec FP puts out a little over 60 PSI. But AC Delco or Delphi pump only. The cheap versions dont hold up.

 

[Schurkey]

It's a WALBRO/TI 255LPH UNIVERSAL EXTERNAL INLINE PUMP, GSL392

EXTERNAL pump? That doesn't sound right.

Purchased online? I'm told that the Walbro pumps are heavily counterfeited.

But even if it's genuine, it could still be wounded.

And what do you have IN the tank, that this pump is trying to pull through? Did you remove the original pump, or is it still there? How about the original filter sock? A partially-plugged filter sock will be hard to pull fuel through during times of high demand.

Don't forget to test the GROUND side of the circuit for voltage, too. Again, test near the pump. Anything over 1 volt is excessive, lower is better. Remember, the voltage actually doing work at the pump is the supply side minus the ground side. EXAMPLE: Your alternator puts out 14.2 volts. The pump--when running--has 12 volts just like you said. So 2.2 volts are being lost on the supply side. You have 1.5 volts on the ground wire near the pump. 12v - 1.5v = 10.5 volts actually powering the pump. 14.2v - 10.5v = 3.7 volts wasted to poor connections, failed relay or switch contacts, or undersize wire. Yes, GM uses undersize wire in the fuel pump circuit, the figures I use here are not too far away from typical for these old trucks that now have some corrosion in the connections.