TECH TIP: Diesel Ram 3500 Lacks Power Under Load After Repairs

TECH TIP (courtesy from ALLDATA)

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 A 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:–base–5-9l-l6-diesel/fuel–fuel-pump-and-sending-unit

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!