Oldsmobile/Buick Repair: Bravada problem, fuel pressure guage, fuel pressure gauge

Question
I have a 2000 oldmobile bravada that I have owned for 18 months. It has not had any repair work of any type done to it. It has had regular maint. but that was over 3 months ago. The day before yesterday my daughter called from school stating that she could not keep the bravada running. I went to the school and got the bravada to run after several tries. Once running, I drove it 3 miles. When I returned to the school, I put it in park, left it running and got out. It cut off and it took about 5 minutes to get it running again. That time it stayed running the 18 miles home. A fuel pressure gauge showed that once running the pressure dropped to under 40 lbs. and fluctuated up and down while idleing. The fuel pump and fuel pump wiring harness were replaced. The bravada cranked and ran. The fuel pressure guage remained steady at idle speed and dropped about 4 lbs. when put in gear but also remained steady. I drove it 8 miles into town, making 2 stops along the way. At stop number 3 it again took several minutes of cranking before it began running, just like before. Once running, I drove it home. This morning it started right up and my husband drove it 12 miles and made one stop without any problem, then it did the same thing. The check engine light has not come on. Can you suggest any other steps. Thanks. Cheryl-------------------------
Followup To
Question -
I have a 2000 Olds Bravada that is not staying cranked. It is also not cranking easily. This problem began yesterday. No problem previously. It turns over fine but will not crank and if it does is does it will not always stay cranked. The check engine light is not coming on. We were told that it sounded like the fuel pump and that GM had had problems with the newer model fuel pumps. We replaced the pump and pump wiring harness, but the problem persists. Can you suggest anything? Thanks, Cheryl
Answer -
This statement makes NO SENSE :

It turns over fine but will not crank and if it does is does it will not always stay cranked.

FIRST let's get the terminology correct.

When you CRANK the engine is when you are holding the ignition in the START position and can haer the engine turning over.

Engine RUNNING is established AFTER you release your hand from the ignitionkey and the key automatically comes back to thr RUN position at which time the engine is RUNNING.

NOW, Restate your question.

Also, What mechanical work or ANY kind of work has been performed on the vehicle recently ?. As most problems that occur after a recent repair was made can be traced back to the area of where the repair was made as a vacuum line may have been knocked loose or a wire connection came loose, Look around in the area where work was performed.



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Answer
When you replaced the fuel pump was there any excessive debris within the fuel tank ?.

Have you tried adding some DRY GAS to absorb any moisture accumulation within the fuel tank ?.

When was the fuel filter changed last ?.

The ONLY other possibilities are:

1. Intermittent faulty crank shaft sensor.

2. Intermittent faulty ignition module.

4. Intermittent faulty ignition coil(s).

5. Intermittent faulty fuel pump voltage supply from the
  vehicles computer.

Intermittents are very very difficult to diagnose as you have to have the actual fault occuring while your doing your test procedures.


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