96 s-10

[drbrown]

this truck wont start sometimes. sometimes it will start & run just fine aalthough it has a miss . i have replaced all kinds of parts.i'm wondering if my ignition switch is bad. i have a friend who's truck had the same symptoms & the new ignition switch fixed it.if you have experienced something like this i would like to hear your ideas. thanks,danny

[drbrown]

in my previous thread i failed to say that my engine is a 4.3 v-6 thanks,danny

[MT-2500]

Originally Posted by drbrown

this truck wont start sometimes. sometimes it will start & run just fine aalthough it has a miss . i have replaced all kinds of parts.i'm wondering if my ignition switch is bad. i have a friend who's truck had the same symptoms & the new ignition switch fixed it.if you have experienced something like this i would like to hear your ideas. thanks,danny

On the ign switch check for power in and power out key on.
Get a good wiring diagram for poer circuits in and out of switch.
When no start you need to check for lose of fuel pressure or lose of spark to plugs.

Post back what it is losing.

Any codes or check engine lights on?
Does engine crank good?
Can you hear fuel pump run on 2 second prime up key first turned on?

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.