I have a 99 Dodge 2500 (2wd, manual 5 speed).

In January, the lift pump died, and took out the injector pump with it. The injector pump was replaced with a rebuilt VP 44 pump. The lift pump replaced with a Fass DRP 02 lift pump.

A few weeks after installation, the pickup would not start. Cranked, but would not fire up. Tried it the next day, fired right up. I was told that the Fass pump put too much pressure on the injector pump and pushed fuel on either side of the diaphram of the injector pump (basically flooding it.) So, they said to hook up the Fass pump so it would not "turn on" when the key was turned, and push too much fuel to the injector pump. Hook it to a circuit that was open. I bought an oil pressure valve and connected it to the top of the oil filter canister. The Fass pump does not pump until the engine starts and there is a minimum of 5 to 9 pounds of pressure, closing the circuit, and grounding the Fass pump, enabling it to begin pumping.

O.K. seemed to be working. About a month ago after exiting the freeway, the pickup started "galloping." It didn't die, but kinda chugged, like it wasn't getting enough fuel. I parked it and left it running. It idled rough. Turned it off, and restarted it. It ran fine. I changed the inline fuel filter between the Fass pump and the fuel tank thinking it might be plugged. There was a small amount of grit in the filter. Checked out my big fuel tank at home and discovered that someone put the wrong filter on the big fuel tank. Possibly causing some grit to get into the pickup's fuel tank. Changed the filter on the big tank. Checked it out, it's clean. Two weeks later, same thing. Changed the pickup inline filter, small amount of grit, but not enough to call it plugged. Then it ran O.K.
Two weeks after that, while in town, the pickup would not start. Cranked, but would not fire up. Changed the inline filter again. (The "old" one of 2 weeks looked clean.) Pickup would not start. Just cranked. Sat for approx. 30 minutes, tried it again, fired right up.

Took it out about 3 hours later, ran fine. Went up a rough graveled road, (approx. 8% grade), for a test run, and it started "galloping" again. Made it home (approx. 10 miles). Turned it off, started it, ran perfectly.

Took the fuel tank off to see if there was any debris in it. A little. Noticed that the screen on the bottom of the sending unit had a hole in it from it rubbing on the bottom of the fuel tank. Maybe the grit got in through the tear in the screen?? Cleaned the tank, blew out the fuel lines, installed a fuel pressure gauge to make sure my Fass pump is pumping correctly. Waiting on a new screen for the sending unit.

Today, I filled a 5 gal. bucket with fuel, (approx. 6 1/2 inches deep), set the sending unit in it, and hooked it to the Fass pump. (I also put a 5 gal. bucket under the fuel return line to catch the fuel sent back from the injector pump.) I bled the air out of the line, and the pickup fired right up. (It takes 7 to 9 seconds from when the engine starts, for the fuel pressure gauge to reach 15 1/2 pounds of pressure.) After approx. 2 -3 minutes, I turned the pickup off. I could hear the fuel running back into the bucket that the sending unit was in. It was like the check valve on the sending unit was not holding, and when I checked the fuel return bucket, there was approx. 4 1/2 inches in it, and only 2 inches in the sending unit bucket.
Is this normal? I'm at my wits end!
I don't know what else to do, and I need some advice.
Thanks very much.