Hard Starting
daw280z
02-12-2009, 04:51 PM
Help !!!
My 96 silverado with 5.0 will not start unless I prime it with fuel or starting fluid. It thens runs fine all day until it is shut down (for more than 2 hours) then it is primming all over again. The fuel pump works about 40 psi and changed the fuel filter, no change. Thoughts? Dave
My 96 silverado with 5.0 will not start unless I prime it with fuel or starting fluid. It thens runs fine all day until it is shut down (for more than 2 hours) then it is primming all over again. The fuel pump works about 40 psi and changed the fuel filter, no change. Thoughts? Dave
MT-2500
02-12-2009, 05:47 PM
Help !!!
My 96 silverado with 5.0 will not start unless I prime it with fuel or starting fluid. It thens runs fine all day until it is shut down (for more than 2 hours) then it is primming all over again. The fuel pump works about 40 psi and changed the fuel filter, no change. Thoughts? Dave
Fuel pressure is to low.
You need 65 lbs pressure on a cold start to squirt injectors.
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 and fuel pressure testing guide line.
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.
My 96 silverado with 5.0 will not start unless I prime it with fuel or starting fluid. It thens runs fine all day until it is shut down (for more than 2 hours) then it is primming all over again. The fuel pump works about 40 psi and changed the fuel filter, no change. Thoughts? Dave
Fuel pressure is to low.
You need 65 lbs pressure on a cold start to squirt injectors.
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 and fuel pressure testing guide line.
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.
Automotive Network, Inc., Copyright ©2026