Case Study: Diesel Ram 3500 lacks power under load after repairs

Sept. 1, 2022
The owner of this Dodge Ram brought the truck in because the engine would start and run for about a minute, then stall.

Vehicle: 2001 Dodge RAM 3500, 4WD, L6-5.9L DSL Turbo, VIN 7, Automatic Transmission/Transaxle

Mileage: 172,556

Problem: The owner of this Dodge Ram brought the truck in because the engine would start and run for about a minute, then stall.

Case Details: The technician found the following diagnostic trouble codes (DTCs):

  • P0370 - Timing Reference High-Resolution Signal Malfunction
  • P1691 - Fuel Injection Pump Controller Calibration Error

The technician decided to replace the fuel injection pump (VP44) and clear the DTCs. With a new fuel injection pump in place, the engine idled smoothly and would run without stalling. However, it stumbled and lacked power under load.

An ALLDATA Tech-Assist consultant suggested checking the transfer pump for operation. He advised that, if the rail-mounted transfer pump failed or was weak, it could have damaged (fuel-starved) the old VP44 fuel pump. The consultant also said that if the technician was going to replace the transfer pump, Chrysler/Mopar had an updated in-tank fuel pump and provided this link.

The technician found that the transfer pump fuel pressure was weak and far below specifications.

Confirmed Repair: He removed the transfer pump and installed Mopar's updated in-tank fuel pump and fuel line kit. The technician cleared the DTCs and went for a test drive. The engine ran strong. No DTCs returned. Fixed!

Reprinted with permission from ALLDATA.

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