97 Z71 keeps vapor locking

[mybad_z71]

Hey guys my 97 Z71 with the 5.7L keeps vaporlocking all the time, i gotta shoot it with starting fluid or climb on top and crack the fuel lines. if it sits for more that 2hrs itll just crank. i can hear the fuel pump running its initail prime when the key is turned on, so what could be the cause?

[tblake]

Why do you think its vapor locking? Are you sure its just not low fuel pressure? How many miles are on your truck?

[MT-2500]

Originally Posted by mybad_z71

Hey guys my 97 Z71 with the 5.7L keeps vaporlocking all the time, i gotta shoot it with starting fluid or climb on top and crack the fuel lines. if it sits for more that 2hrs itll just crank. i can hear the fuel pump running its initail prime when the key is turned on, so what could be the cause?

I have not saw a vapor lock in 20 years.
But a lot of weak fuel pumps.
As tblake says fuel pressure.
Check that fuel pressure and post back what you have or do not have in pressure.

[mybad_z71]

sorry guys, went old school with the vapor lock, its what it just remeinded me of especiall living in phoenix where its been over 110 last 2 weeks. whats the easiest way to check the pressure

[MT-2500]

There is no easy button on it.
But it is not hard to check.

Just.

Find the fuel rail test port in pressure line at top rear of engine and hook a fuel pressure gauge up.

Engine cranking should be 64-65 lbs.
Engine running specs are 60-66 lbs.
The only true test of 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.
A good strong pump will have 95-105 lbs with return pinched.
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 your fuel pressure readings for more help.

[tblake]

Where is the best way to pinch off a return line?