Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail [email protected] with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.
Vehicle: Sterling L-Line Beverage Delivery Truck
Key components: Caterpillar 3126 engine, Allison MD3060 transmission
Scenario: This truck was towed in after it suddenly stalled while driving and would not restart. The driver reported an odd noise before the engine stalled. Specifically, he stated the noise sounded like it was out of power steering fluid.
Clues:
- The engine was scanned and had injection pressure faults, occurring several hundred times in the past hundred engine hours
- Live data shows low pressure during start attempt
- Deadhead testing of the high-pressure pump on the truck produced 4000 PSI during cranking.
- The engine was tested for internal high pressure oil leaks using shop air and none were evident.
- A new high pressure pump, pressure sensor and control valve failed to improve this condition.
