Fuel pump question

Ok, here it goes. For about the last 3 weeks my 97 blazer 2dr 4.3 has been intermitenly shutting off. Couple times a stop light and couple while travling down the road. The fuel pressure goes to 0. I have spark , air, just no fuel.If I leave it for several hours, usually overnight, it fires right back up like nothing is wrong. fuel pressure reads 55lbs. It will run great for 3-4 days and then it happens all over again. It seems to happen only when its up to operating temp. I have tried to fix it myself with no luck.Here is what I have done so far. Replace fuel pump relay,Replace oil pressure switch,New plugs,wires,rotor.Is it the fuel pump? If so why does it run great after it cools.I replaced fuel pump about 8 months ago. My mechanic and myself are at a loss. I even ran a wire from the fuel pump test lead to a switch then to battery.thinking if it died again I could hit the switch and pump would come on. It died last night and I hit switch. NOTHING. Fuel pump did not come on even from test lead. I went out this morning and it fired right up.WHATS GOING ON!!! Any help would be greatly apreciated.......

If it has voltage or you jumped voltage to it and has ground.
And fuel pump does not run or runs and puts out low pressure
You fuel pump is getting bad.
Depending on how it is going bad but some will get hot and quit or lose pressure.
Only other thing to check is for good ground and check the plug in wire at the fuel pump. Some go bad there and lose connection and some fuel pumps come with a new wiring plug to fix that problem.
Did you put in a new GM oem pump or after market pump?
Your fuel pressure should be reading 60/66 lbs of pressure.
55 is way to low.

Pressure check 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.
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.
Post back fuel pressure readings.
MT

I had a Carter pump fail after 13 months (of course, the warranty was for only 12 months).

Same symptoms as yo describe. Sometimes runs fine, then just quits. Let it sit overnight, fires right up. Turn it off, won't restart till the next day.

I put a Delphi pump in for the third go-round.

Thnxz for the input.I just picked up a bosch fuel ($400) OUCH.It has lifetime waranty so if it goes again I am covered.I'LL let you know if it did the trick.

Hello back again. Just got back from mech. put new bosch fuel pump in and new fuel filter.guess what, my fuel pressure is still at 55lbs.the funny thing is now when I test the pressure with the test lead it is at 62 lbs. Any ideas?? thanks

Hello back again. Just got back from mech. put new bosch fuel pump in and new fuel filter.guess what, my fuel pressure is still at 55lbs.the funny thing is now when I test the pressure with the test lead it is at 62 lbs. Any ideas?? thanks

Are you checking with engine off or running?
Did the new fuel pump fix the engine running problem?
On the fuel pressure test make sure the gauge is right on the money.
Then run the fuel pressure test as I outlined in upper post and post back pressure readings.
MT

I would try putting in a new ignition switch. What's happening is the switch is not supplying power to the pump at all times. Had a very similar problem with a 2000 alero. Sometimes it would start other times not. Also...... the 97's are known to have ignition switch problems.