Diagnose This! Rough-riding wrecker – November 2008

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 Dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

Vehicle: 2000 GMC C7500 rollback wrecker

Key components: Caterpillar 3126 engine, manual transmission and air brakes. Vehicle has 250,000 miles on it.

Scenario: This rollback wrecker runs rough and occasionally stalls only when the power takeoff is engaged. Faults are logged on all six injectors (as shown in photo 1).


  • Injector solenoid testing at fault occurrence shows “short” on all six injectors (see photo 2).
  • Disconnecting the wiring harness at the valve cover pass though changes the test results to “open” (see photo 3).
  • The rocker cover was removed and the wiring harness appears undamaged.

Damon Russell has been involved in the truck repair industry all his life. He is ASE Master certified in all six categories, holding 46 ASE certificates in all. He has been actively working to improve the trade by working with his local trade school’s advisory boards, judging SkillsUSA competitions, participating in evaluating NATEF program standards and ASE test writing workshops. He is also an active member of iATN.

Damon and his wife Kathy own and operate Fleet Guardian LLC in Bridgewater N.J., a small five bay garage serving the needs of local and national commercial fleets of light-, medium- and heavy-duty trucks since 1992.

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