95 jimmy fuel problems

I hope someone out there has some insight,
I have a 95 Jimmy that has been giving me trouble starting, sometimes it does and sometimes it doesn't. The engine is trying to turn over and I can hear the fuel pump humming under the car. I had it towed to a local mechanic because it wouldn't start and of course when he looked at it later that day it fired right up and he could find nothing wrong with it, I had him change the relays and fuel filter while he had it, ran good for a few weeks and once again won't start so again I had it towed to a dealer, and once again fired right up after they got it inside, They suggested I changed the oil pressure switch and try a new battery, so I did and it ran fine for about a day. Next day fired right up for work and when i got off nothing, third time towed-third repair man, got it inside fired right up, They said that can't tell what's wrong because it's running fine, but come on there's got to be something wrong or it would be starting every time, they say maybe the fuel pump could have problems, I would be interest in some other thoughts.
Thanks

Remove the top Vortec name plate.

Remove the round valve in the top of the motor under it.

Peer down into the hole with a flashlight and check for fuel smell, pools of gas and golden washed spots.

Haven't got a chance to check under the vortec name plate, but will check that out later today or tommorrow, This morning I did try to start it and of course it did not, but I added a bottle of dry gas and tried again after 2 hours and it did start but idled really rough for a few minutes and died out. Did restart but kept dying out a few times.

A lot of the time checking for washing via the throttle vane hole isn't accurate. Pull the upper plenum to actually see everything.

A lot of the time checking for washing via the throttle vane hole isn't accurate. Pull the upper plenum to actually see everything.

Local autoparts stores carry the gasket for the upper intake manifold for about $10. It is cheap enough and easy enough that you really cannot afford not to do it. No RTV is required on reassembly of the upper plenum. Heck, buy two. I have a spare upper intake gasket hanging on my wall ready for the next time I check it.

Tools required:
~T30 torx bit (for removing Vortec cover)
~10mm deep well socket & rachet (for removing the bolts and nuts holding the plenum).
~Some masking tape to label the sensors & vacuum lines you will disconnect
~torque wrench (remember that 12in-lb = 1 ft-lb)

Couple of points:

1. I use a box where I traced the gasket and insert the bolts and nuts in their respective locations. Not essential for this job, but makes reassembly easier and it is good practice for other jobs.
2. Make sure you thoroughly remove all traces of gasket material prior to reassembly. A nice sharp putty knife held almost horizontal works well. Don't put scratches in the metal. Not as critical as the lower intake gasket or the heads, but still good practice.
3. Make sure you put the color bead of the gasket (orange or green usually) facing up. Torque the bolts to spec (92 in-lbs if I recall, or about 8.5 ft-lbs). Check your engine specification section of your Haynes manual. FYI I find Haynes more useful than Chilton. But I have both.

As none of the bolts on the upper plenum go into the coolant jacket, you won't need to use teflon sealant for these bolts.

Pulling the upper plenum cover is not as "easy" as you guy are suggesting.

There is a lot of crap to remove just to take the cover off and requires the most work out of the whole process.

Best to check through the IMTV valve hole for washing first and go from there instead of wasting time removing the top cover twice to do the repair.

Also, the EGR should be checked in this situation.