Medium and Heavy Trucks
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Hi my name is***** will be glad to try to help. What is your serial number and engine make/model? Any particular color smoke? Do you get full throttle sitting still? Is this only operating under a load? Check for restrictions or leaks sucking air between the tank and pump causing a low fuel pressure problem. Verify you have good fuel supply pressure. Try running from a separate fuel source for test purposes or installing a clear hose inline on the suction and return to check for air bubbles. Let me know
Thanks for the clarification. Check the hydraulic filter internally and oil for fine metal/debris that would flag a pump or component failure occurring. If clean, inspect the relief valve cartridge for debris or damaged o rings, etc causing a bypass in pressure. If the relief is not sticking open or found to be bypassing, etc. then test your pressures in those circuits to compare to OEM specs for still a potential pump or control valve problem. In some cases pump problems initially are not flagged by metal/debris. Verify both Pilot pressure and main pressures are in specs.
Usually after pump or major component failure the system has to be cleaned out and flushed properly and the control valve inspected for debris in the ports or signs of contamination.