I can talk from experience sine I just replaced mine. Pressure check tells a lot. Mine was long start times off and on. When I used the gauge to test it. It was bouncing all over the place. Once I dropped the tank and cleaned it out and put in new Delphi pump. Its been great every since. Luckily mine was almost empty at the time. I found things in my tank that would make one scratch their head. lol. Factory pump was loud enough to know it was working. Delphi is quiet as a mouse. Once replaced. Starts every time and fuel pump pressure is stable when tested. No more bouncing around. I can say it wasn't hard and I did it by myself with my floor jack. Slowly drop the tank while underneath the truck to where you can reach up and release the connections, then drop down pull it out and your good to go. Good Luck. These guys are great in helping with any questions and patience with questions you may have.

 

So...Update.

I found the Schrader(?) valve I didn't think I had, so I got away with a Harbor Freight FPG. Put the gauge on, turn the key to on, no pressure. Turn the key to start, no pressure. Thump the tank with a rubber mallet while starting, truck fires up and reads 40 PSI on the gauge as long as you hold the throttle to over 2k RPM. Otherwise, pressure drops fast and the truck dies. I did this several times because I was having fun watching what the FPG did while it was running under various throttle positions. During one of the tests, after the truck died, the pressure shot back to 40 PSI. So, I started it and it fired right up, idled like a brand new truck for about 5 seconds, then chugged and died. I'm ordering the pump tomorrow and I'll come back and regale everyone with the horror story of me trying to replace it.

 

Hmmm.....fp remaining over 40 so long as RPMs are over 2k makes me wonder about the fuel pressure regulator.

I don't know if it's even conceivable for it to essentially block off fuel at high vac and allow fuel thru at lower hg?

But typically an ailing pump will be ill'in (B-Boys shout out) even more at higher RPM due to increased demand for fuel, not the other way around.

Or you may be facing a crank sensor issue...does the PCM kill fuel based upon tach signal or lack thereof?? Most EFI does....

What say the forum? @HeyYou ??

 

Everything seems to point to the fuel pump, especially given that once the fuel tank is hit with a mallet, the fuel pump starts up. The only wildcard I'm hearing is the 2K idle - makes me wonder what the condition of your battery is. A load test of the battery would be the last thing I'd check prior to replacing that pump with the Delphi unit.

 

The battery is a good thought I hadn't considered!

 

What does voltage look like at lower RPM? Is alternator output where it should be? Wonder if the pump just isn't getting enough power at lower RPM to build full pressure. I agree though, smacking it with a mallet making the pump run is definitely not a good sign.

 

I completely agree, it's just bizarre that after said smacking it would only run ABOVE 2k rpm. I'd think if the battery allows for repeated cranking and re-starting it's got enough juice to keep the pump happy for awhile at idle.

As I said, bizarre. I hope we get a follow-up, I'm just curious now

 

THE OPERATION WAS A SUCCESS!

Man, I was stressing hard about this. I'm no mechanic. It took me three days to convince myself that if I paid for a pump, I was actually going to put it in myself. I watched a video of a guy doing it in a professional shop and one of a guy doing it in his driveway.
Even with only one jack, a pair of jack stands and the limited tools I have, it was amazingly easy. I mean, not so easy that I'd buy cheap pumps and replace them every couple of months. The hardest part was breaking the strap nuts loose. I am not the behemoth I was 20 years ago. Anyway, dropped the tank, took out the old pump, put the new one in and the truck fired right up. I did not realize the starting, idle and acceleration issues I had until they weren't there anymore!

Again, you guys have been a huge help! Thank you all for your input, tips and, ideas.

 

That's awesome to hear. I thought it was going to be real hard myself but after doing it. I wouldn't hesitate to do it again if needed.