General Discussion

[LAWRENCEM]

Hello all from first time user.

                Have(just acquired) 1995 Chevy 7500 series truck , engine sn 9GK23320, former NC DOT truck. Was functioning correctly when picked-up. At about 55mph on a rough hilly section of roadway, truck seemed to lose engine rpm's forcing a downshift to the next lower gear. After a few minutes is ran better. Purchased a new fuel filter(filter mounts upside down on water seperator), truck started and operated O.K.. Carried a load of dirt in dump bed on its first work related task, ran OK to drop site(rough off road ,off level area). On return to base truck got up to speed, but again lost pulling power(with no load in dump). After a few minutes, started running O.K.. Second trip with loaded dump, same thing, good going there, running poorly on return to base. Added 20 gal fuel to what was about a 1/4 tank, truck started OK but right away ran really rough and just limped back to base. Pulled fuel screen from governor/pump, 100 percent gummed with tar. New fuel screen and check valve, pulled tank (cleaned out, refueled), engine started, ran a minute or two and stalled. There is no pick-up screen in fuel tank(no part available from GM as per parts dept.), no fuel filter in line to Gov/pump(just the screen), does "NOT" have primer on post pump filter. Now for the question related to this long winded lead-up. WHAT is the best way to prime this system? The filter has a "T" fitting on the outlet side with plug on bottom of "T"(line going to fuel galley on rear of engine), would a petcock with hose barb for a portable hand pump be a good place to try and prime from? If so what might the thread for this "T"/ plug be, and does cat have a part other than the plug? Is there a simpler way of priming, or does it sound like a different problem? Please "HELP". Thanks in advance, Larry.

[dave10010]

You can add a fuel priming pump to this engine (1011533), which will make filter changes easier. That is not the cause of rough running though. You should remove the fuel transfer pump piston and inspect the internal valve. Possibly some of that tar made it to the transfer pump. The transfer pump is under the 3 bolt cover on the top of the governor. Fuel pressure should be 45-55 PSI at rated RPM.

[LAWRENCEM]

Thank you Dave,

                       I did finally get it primed by connecting a hand pump to the water seperator drain on the secondary(no primary filter exists-need to add one-any suggestions?) fuel filter.

Could I have done any damage to the seperator by doing this? Truck seems to run well now, but really have to see under load. Does the fuel pump section of the governor have access to check and clean just by removing the 3 hex head screws, or does the governor need disassembly?

                                                                   Thanks again, Larry

[dave10010]

No need to remove governor. Just remove the 3 screws and top cover of transfer pump. You can remove the transfer pump piston and sleeve for inspection. Replace the seals when reassembling.

[LAWRENCEM · Accepted solution]

Thanks again Dave, you've been most helpful. Larry

[Bryon47diesel]

Hi, I have a 1990? Topkick (124,000 miles) with the 3116 engine and am trying to work out some fuel and intake heater issues. When I bought it, the truck started hard, ran rough and smoked alot until hot. Before I get serious about replacing injectors, I am trying to rule out everything else that I can. First, I have already replaced both fuel filters, air filter, and engine oil and filter. I also replaced all of the hard fuel lines from the tank to engine with rubber fuel hose to eliminate any possible air leaks. The truck will start fairly easy now but it seems to run rough and misfire if you give it any throttle until the temp gets up close to operating temp. It also still smokes excessively until hot. I'm not certain if the fuel transfer pump is even working because I don't seem to have any fuel pressure at the fuel filter. Will low fuel pressure to the head cause smoke and misfiring?

The other issue is the engine intake heater. I replaced the control relay on the top of the intake manifold and it worked for a while but now the relay seems to have failed again. I'm wondering if I had the two small wires reversed on the relay. Any help on the polarity would be appreciated before I put another new relay on it. The dealer doesn't seem to want to offer any assistance on this.