I have a 1994 Chevy Silverado 6.5 L that apparently is plagued with trouble. When I bought it a couple months ago, I replaced the fuel filter and the lift pump. Upon replacement of the lift pump, I found that the previous owner had wired the old pump so that it ran all the time. I changed it to the original configuration. I drove the truck several days to work and back with no issue. I have always had a problem with just barely toucing the accelerator and the RPM's continue to rise as if I was pressing harder and harder even though I am holding a steady pressure. It makes driving 45 MPH very difficult. I was leaving work one afternoon and the truck stalled in the parking lot. It would not crank after that. I had it towed back home, and I replaced and relocated the PMD. I started up after several hours of trying to bleed the fuel system. There was only about an inch of fuel in the filter housing. I jumped the lift pump relay and watched the housing fill with fuel. I didn't notice any bubbles in the fuel. Then I decided to pull my boat with the truck. As I was travelling down the interstate, I noticed that the truck was smoking heavily when going up hills and seemed to not have the power that one would expect. I had also been having a SES light that would be on at idle, go off with higher RPM's. I found that the vacuum pump was not working so I replaced it yesterday. That resolved the issue with the SES light. I went to eat lunch, and the truck did not want to start in the parking lot of the restaurant. It did start on the third try, but when I reversed out of the parking space, it went about two feet and stalled again. Luckily, it started up and I was able to get it home. I suspected the previous issue had returned so I removed the filter housing. Sure enough, there was hardly any fuel in the housing. My filter is the type that has the plastic top and retainer ring all-in-one. I am wondering if it is not sealing and letting air in. I don't notice any fuel leaks. I have not tried to replace that OPS. I don't really have a way to leak check the fuel line coming from the tank, so I may just replace that line. I thought it might have been a pin hole in the lift tube in the tank, but the tank is completely full when this happens. This truck is nickel-and-diming me to death, and right now I have no other means of transportation. Can someone suggest something I might try or how the air might be getting in the system? So that's the sum of the problems at this point: 1. Rising RPM's with steady accelerator pressure 2. Air getting in the fuel filter housing. I need new tires, but I don't want to spend that kind of money on a money pit that is never going to run.

 

Sounds like the lift pump isn't running all the time to me. I would investigate why that could be happening. I'm no expert on the 6.5 chevy diesel but i assume the computer tells the lift pump to come on. Maybe the sensor that tells the computer to run the pump is gone or there could be a wiring issue between the computer and the pump relay. If you wire the pump to stay on all the time like it was when you bought it, are you still having the same problem. the fuel line from the lift pump to to the engine is pressurized, so if that was leaking, you would find the leak fairly easily. Another way to tell if the lift pump is working is to get a helper to cycle the key on and off and pull off the fuel cap and put your ear up to it. the pump should come on and run for a couple of seconds and then shut off. Could be something as simple as a relay starting to fail or a loose connection somewhere. Good Luck!