I got a friend working on 95 3500 throwing a code 78 hes replaced the sylenoid with still no luck anyone know what else it could be he did say it was losing power when running I thought it might be the turbo its self.
Have good vacuum from the pump? If so, could be wastgate actuator. Should have 14/15" (I think) at wastgate at idle, and actuator should have some resistance if you try and pull it.
Howdy Check the vacuum at the vacuum pump, should be 26" and real steady. If the gauge is flopping around replace the pump. Check the vacuum at the wastegate solenoid on the drivers side valve cover. Vacuum should be the same as at the pump on the line coming from the pump Ok so far move to the waste gate actuator, 26" at the line connector at the actuator. Many times the lines will crack too. Vacuum hose will sufice for a temporary repair until new lines can be obtained. Common issues are poor vacuum and the solenoid goes south. About $45 for the solenoid. Be sure if the vacuum is good that the waste gate moves freely back and forth with the engine off and is tightly shut with the engine running.:stir: Check it out and let us know. MGWwaytogo
