4.3 won't start

I have a friend with a '98 Silverado with the 4.3 6 cylinder engine and if it starts it runs just fine...but it only starts about 25% of the time. If you give it a shot of starting fluid in the intake it starts up every time. The fuel pressure is 55psi. The truck has 232k miles on it and is kept in good mechanical condition. Any ideas?

You need more fuel pressure for injectors to squirt on a cold start.

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.

MT-2500...thanks for all of the info...I passed it to my friend and he will get started on it this weekend. I'll let you know how it turns out.

You are welcome.
Good Luck
And let us know how it goes.

I talked to my friend and he replaced the fuel pump and not only did it fix the starting problem but he says the truck runs much stronger then it ever has!!!

I talked to my friend and he replaced the fuel pump and not only did it fix the starting problem but he says the truck runs much stronger then it ever has!!!


Good.
Thanks for posting back how it went.
Good luck