1990 Chevy k1500 5.7. 156k miles. I had some starting problems a while
back, I isolated the problem to the fuel pump loom connector or the fuel
pump itself. I attached a fuel pressure gauge at the fuel filter and
sometimes when I'd turn the ignition, I'd get no pressure. Other times
I'd get a good consistent reading.
 I ended up cleaning the connector and the wiring to the ground at the
frame, and for 4 days it ran fine with no problems. When it failed to
start again, I rechecked everything, had voltage leaving the fuel pump
relay, but no pressure. I opened the gas cap and banged on the tank to
see if that helped, nothing. Finally I was able to get it to start while
I bounced the truck up and down, it sputtered a bit and then fired up,
and it's fired up ever since (4 days and counting).
 I went off-roading a month ago and hit some pretty steep
inclines/declines and bumps and am wondering if crud broke loose in the
tank and is floating around wreaking havoc. Or am I just looking at a
dying fuel pump? I'm working on emptying the tank so I can drop it and
take a look inside.
 I use Chevron Techron Fuel Injection cleaner every tune up, and am
wondering if theres anything out there that might address more potent
crud in the gas tank? Or should it be cleaned out professionally? If my
tank is fairly clean, and have full access to the fuel pump, is there
any way to do a complete check to make sure it's not dying? I'm not to
clear on the mechanics of the pump, which is why I ask. I was even
thinking of, once the tank is out and away, having an access port/door
cut into the truck bed so I can easily access the pump at a later time.

Thanks for any info.