If you explain the circumstances to Rock auto, they'll probably work with you. Besides, the pump should have at least a one year warranty.

Probably be a good idea to remove the pump relay when testing the level sender

EDIT: keep in mind when testing the float, that the buffer, (electronic shock absorber) will delay the reading at the dash unit.

 

I hooked up my Auto Enginuity scanner to see how many gallons of gas it said that the tank has, and according to it there's nine gallons left, with the gauge now reading a little less than half a tank. (On the "percent fuel remaining" scale it only said 7 percent. Not sure what that could mean for my situation.) I've driven about 220 miles on this tank of gas, so that would equal 22 miles a gallon. So unless I somehow gained 4 MPG since replacing the pump, it's definitely inaccurate. I'll have a better idea when I fill up again. So this is most likely a faulty sender then? I've noticed that when I place the truck in park the gauge needle seems to wander a bit. Didn't feel like dropping the tank this weekend, probably get to that next week.

The real reason I was posting though......
I realized I hadn't rechecked leakdown to ensure that the replacement fixed the issue. Nope. After ten minutes the pressure was at 50 PSI. So when I originally tested the pressure/leakdown at the filter, either I got a bad reading because of my "creative plumbing" (likely), or my pressure gauge is faulty (possible). I'm not too upset about replacing the pump in error, since it was more than ten years old and since I plan on keeping the truck, would have needed replacing sooner rather than later. So now, it looks like I am back at square one. Since I've ruled out the pump as the culprit, I guess the leak is somewhere under the plenum.

 

A "wandering" needle indicates a problem with the buffer circuit in the level sender.

 

Is the buffer circuit is located in the pump module?

Still going to check on that pinched wire and repair it, but from what the Captain has been saying, it seems that the sender I got is defective. What a pain in the a$$.

Unless the check valve in the new pump is also defective, it looks like I have a leakdown issue in the plenum. Haven't noticed any leaks in any fuel lines. If I remove the cover will the leak be noticeable from the washing in there?

 

On your 2003, the buffer is part of the level sender and the level sender can be replaced separately from the module. The entire module must be removed to replace it.

If the leakdown is in the plenum, you may or may not be able to see it by removing the plenum. If you have the old style injector assembly, (W engine) there could be a leaky poppet nozzle. If you have the upgraded assembly, (X engine) there could be a leaky injector. Or, the regulator could have an internal leak past the valve plate. In either case, a leak will not be visible. Visible leaks include a leak in one of the lines in the plenum, an external regulator leak, or a connection leaking.

To confirm an internal leak: After determining that the pump module is not leaking: install a shut off valve in the fuel return line, close the valve just as the pump pressurizes the system, then watch for leakdown at the service port. If pressure drops, the leak is definitely in the plenum. This doesn't tell what's leaking, but if there are no visible leaks, and the pressure still drops, you know to look for an injector/poppet or internal regulator leak.

 

Just to update, I replaced the pump/sender yesterday, this time the gas gauge seems to be working normally. Drove about thirty miles on a full tank and the gauge needle is now slightly below full, seems about right. So it's looking like that the other sender was defective out of the box. Rock Auto is covering the replacement under warranty.