Silverado fuel pressure bleeding off

stryped · November 28, 2011

I have a 1996 silverado with 324,000 miles. It is my daily driver. I was having intermittent hard starting after sitting and stumbeling while driving until warm. This does not happen every time.

Anyway started doing a fuel pressure check. Pressure is 60 psi KOEO. With engine running drops to about 54 psi. However when I turn the key off the pressure drops about 30 psi in 5 minutes. I have a cheap Haynes manual. It says to determin if the problem is a leaky injector or check valve in fuel pump to install a fuel cut off in the supply line and see if pressure holds. Is there an easier way to do this? First, I dont know what they mean by a fuel cut off and second even if I did I dont have one.

Can I use vice grips and pinch the rubber hoses? DO I do this when it is pressurized?

I appreciate any help!

markw8 · November 28, 2011

If you can find a place to pinch it, it might work. It should tell you which side of the stoppage the leak is on. Put the guage on, turn the key on, don't start it, when the pressure comes up pinch the line then turn the key off. Then see what happens. If the pressure holds, the problem is in the tank. This could damadge your old rubber fuel line though.

Mark

ChevyTech77 · November 28, 2011

I have a 1996 silverado with 324,000 miles. It is my daily driver. I was having intermittent hard starting after sitting and stumbeling while driving until warm. This does not happen every time.

Anyway started doing a fuel pressure check. Pressure is 60 psi KOEO. With engine running drops to about 54 psi. However when I turn the key off the pressure drops about 30 psi in 5 minutes. I have a cheap Haynes manual. It says to determin if the problem is a leaky injector or check valve in fuel pump to install a fuel cut off in the supply line and see if pressure holds. Is there an easier way to do this? First, I dont know what they mean by a fuel cut off and second even if I did I dont have one.

Can I use vice grips and pinch the rubber hoses? DO I do this when it is pressurized?

I appreciate any help!

You can just pinch the rubber hoses, yes. These engines were known for leaking poppet/injector tubes over time. GM has an MFI kit to replace all of it with that is a much improved design, if you end up going that way.

stryped · November 28, 2011

Do I pinch the supply or return line rubber hose?

ChevyTech77 · November 28, 2011

Both, after pressure builds and pump stops.

stryped · November 28, 2011

If it is not the pump is it safe to drive? This truck has 342,000 on it. Dont want to spend too much on it.

stryped · November 28, 2011

Is there a way to tell if it is both the injectors.rgulator and fuel pump?

ChevyTech77 · November 29, 2011

Fuel pressure bleeding off is only going to affect the vehicle's driveability and in severe cases possibly contaminate the crankcase oil with gas causing it to thin out and possibly cause internal engine damage.

If you pinch off the rubber hoses nearest the engine and the pressure still bleeds down, you'll need to get the upper intake off to tell which component is leaking down for sure. If the pressure don't bleed off, it's in the tank. Pretty simple.