Mississippi Mike

Sorry for this lengthy description but I have done everything I can think of. The truck has had a starting issue since I bought it a year ago. Otherwise, once started the engine runs smoothly even at idle. I installed a fuel pressure gage on the fuel rail test port. No fuel escaped while installing the gage. When the key is turned on, the fuel pressure goes to 55 psi then immediately drops to zero. Fuel pressure slowly increases while the engine is being cranked. Cycling the key from off to on produces fuel pressure each time, but after the initial prime, the pressure quickly goes to zero. No fuel leaks have been found and I have traced both the fuel delivery and return lines from top to bottom. The previous owner had replaced the fuel pressure regulator, probably trying to correct this issue, but I ordered and installed a new Delco fuel regulator, vacuum hose and Shrader valve for the fuel rail port. There was no evidence of fuel when the vac. hose was removed with the engine running. With the engine running at idle, I have 50+ psi with the expected rise at higher rpm, but when you turn the key off, the fuel pressure still drops to zero immediately. No residual fuel pressure at all. The next logical thing would be the fuel pump check-valve. Since replacing the fuel pump is a pain, I installed a high-quality in line fuel check valve by cutting the metal fuel line between the fuel pump outlet and fuel filter. The fuel filter appears to be fairly new. The fuel pressure drop remains the same. Next, I removed the fuel rails and fuel injectors looking for a leaky injector. I tested all eight injectors for resistance, and all produced around 12.2 to 12.7 ohms. Using a twelve-volt power supply and pigtails, I bench tested, energized and cleaned each injector with carb. cleaner and all sprayed correctly. I then filled each injector from the inlet with carb cleaner and found no leading injectors. Fuel injectors remained dry after reinstallation. My truck fuel system includes a return line to the fuel tank. I guess my question is, how can the fuel system maintain fuel pressure without fuel being returned to the fuel tank automatically? Is there a check valve to close the return line when the engine is stopped? If so, I can't find it. Does the evap system control this? The computer is not throwing any codes. I must be overlooking something obvious, and I hope someone with knowledge of the GM fuel system will have an idea. Any assistance will be appreciated, and I thank you in advance.

thank you for your assistance. I will order the wiring diagram and go from there. Yesterday, I again removed the plastic surround on the under hood electrical distribution center. Checked all fuses again. I released the top fuse section and took a look underneath noting no damage. Here is the super strange thing. I checked for power again at the 7 way trailer connector noting that the plug was really dirty. I removed the factory wiring harness from the back side of the plug and cleaned the contacts. I now have power to the trailer plug but the issue with the dead fuses is unchanged. I am baffled. How can I have power to the trailer plug at the rear of the vehicle and all of those fuses testing open? The horn and windshield washer pump work well too and both of those fuses are open. I tested all of the fuses again and both indicate continuity with my multi-meter. I ordered a replacement trailer plug in to replace the old dirty (corroded) one. I will post the solution once I have this mystery figured out. Thanks again for your words of wisdom.

I am a new member on this great GM-Truck site and have an issue with a recently purchased truck. It is a 2000 Silverado 2500 with the Z82 trailer package. This work truck has apparently been run hard and put away wet all of it's life with 160,000 miles on the odometer. I purchased as a farm truck and don't intend to make it a show truck. It runs well (after replacing the Mass Air Sensor and air filter) and will serve my purposes to use around my property. I don't intend to put this truck on the road, however, I would like to be able to pull my 25' camper to local campgrounds on occasions. I tested the factory installed 7 way trailer connection and found no power. I opened the 12 volt main fuse panel under the hood and found no power to any of the trailer related fuses. See attached photo of fuse legend. Yellow highlight are the dead fuses. I pulled each fuse individually and checked with my multi-meter to confirm continuity. I removed the surrounding plastic cover from the under hood fuse panel and both stud 1 and 2 are powered. All of the large fuses along the top of the panel are powered. The truck came with an aftermarket trailer brake controller and it is plugged into the under dash panel in the second from the left top plug in. There appears to be no power to the brake controller. I am going out this morning to continue my testing of the trailer circuit. I need to discover if the wiring is shorted or open. I guess my main question is this: What powers the trailer related fuses in the main fuse panel under the hood. It is interesting that the windshield washer pump and horn are operable even though those fuses indicate that they are dead. Any assistance will be greatly appreciated.