1996 Silverado fuel issue

[ejazz]

I have a '96 Silverado, 350 with the throttle body. Went to start it today and no fire. I can hear the fuel pump come on then off. The truck will start and run if I pour a little fuel in the throttle body. When depressing the fuel valve on the feed line, some fuel sprays out when the engine is turned over but seems like there should be more pressure. Anyone know what the fuel pressure should be if I check it with a guage at the fitting? Any other ideas? Thanks.

[j cAT]

Originally Posted by ejazz

I have a '96 Silverado, 350 with the throttle body. Went to start it today and no fire. I can hear the fuel pump come on then off. The truck will start and run if I pour a little fuel in the throttle body. When depressing the fuel valve on the feed line, some fuel sprays out when the engine is turned over but seems like there should be more pressure. Anyone know what the fuel pressure should be if I check it with a guage at the fitting? Any other ideas? Thanks.

the pressure should be around 60psi...check ground wires and voltage at the pump...if good and pressure drops rapidly on pump shut down the pump is bad..

replace fuel filter,fuel pump relay when fuel pump is replaced................get the dephi pump...airtex is to be avoided..

[MT-2500]

Originally Posted by ejazz

I have a '96 Silverado, 350 with the throttle body. Went to start it today and no fire. I can hear the fuel pump come on then off. The truck will start and run if I pour a little fuel in the throttle body. When depressing the fuel valve on the feed line, some fuel sprays out when the engine is turned over but seems like there should be more pressure. Anyone know what the fuel pressure should be if I check it with a guage at the fitting? Any other ideas? Thanks.

96 5.7 code R engine is very sensitive on cold start fuel pressure.
Specs is 60/66 lbs of fuel pressure.
They will run all day on 50-55 lbs and start warm.
But you need 63-65 lbs of fuel pressure to squirt injectors on a cold start.
Also make sure pump runs on engine cranking.
Also you need a good strong pump that will produce 95 or more lbs of direct fuel pressure toi mantain 60/66 lbs of running pressure.


A good fuel pump test.
Since it will not start and run.
Do as much of it as you can without engine running.
Then after problem is fixed rerun full test.
The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

[ejazz]

Thanks fellas. I should have a chance to dig into it tonight and will let you know what I find.

[ejazz]

Update: Replaced the fuel pump with a new one from GM. Truck started right up and ran great for a day. Then started to spit and hesitate on acceleration. Wouldn't start one day and again, will start by spraying fuel in the throat.
Checked fuel pressure again. 40 psi and drops to 20 as soon as pump turns off. Here is my question. When I replaced the pump, I reused the fitting in the tank that connects the fuel pump outlet to the hard line. It is the unit that slides up and back down once the new pump is in the harness. Could this be leaking and not allowing pressure to build. The new pump came with a hose and two clamps, probably to replace the contraption?

I know the problem is at the pump because I pulled the line out of the back of the upper intake and held my finger over the feed line and engaged the pump. Still 40 psi. This is a direct line from the pump and the fuel filter was changed. I also ran a direct ground to the wire harness at the pump to rule out an electrical issue or low voltage. Voltage was 11.8 volts. Is the pressure guage reading at the port supposed to remain constant (no drop) once the pump turns off? Mine drops from 40 to 20, could it be leaking down at the pump?

[jyount]

it shouldn't drop that much, it should hold pressure a while. Sounds like you have a bad pump, that sucks man. Did you use a gm pump?

[ejazz]

Yes, GM pump.

[ronaldk]

I would pull pump and install the new internal hose they supplied. Old line probably bad. Good luck