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Date: Aug. 2, 1996
Models: 1994 - 1996 (BR) Ram Truck (also applies through 1998 12V models)
NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH THE 6.9L CUMMINS DIESEL ENGINE.
The Bosch P7100 inline fuel injection pump may be affected by fuel supply pressure variation. If the fuel supply pressure is low or pulsates excessively, the following symptoms can occur:
This bulletin contains diagnostic information supplemental to 1994, 1995, and 1996 Ram Truck Service Manuals and should assist in the diagnosis and correction of the above Symptoms/Conditions.
1. Verify that the fuel shutdown solenoid linkage is properly adjusted. Improper adjustment could affect fuel delivery in the injection pump. Refer to the 1996 Ram Truck Service Manual (Publication No. 81-370-6108), page 14-106, regarding fuel shutdown solenoid shaft adjustment.
2. Verify that the fuel transfer/lift pump supply pressure to the injection pump is within specifications. Normal fuel transfer/lift pump pressure specifications are 17 - 22 psi at idle and of 25 - 35 psi at 2500 rpm (no load).
3. Place a drain pan below injection pump.
4. Remove banjo bolt and gaskets from fuel inlet line fitting at side of injection pump (Figure 1).
5. Install Special Tool 6976 (SPX Miller) and tool gaskets from tool kit 6977 (SPX Miller) in place of the banjo bolt (Figure 2). Tighten tool into injection pump.
6. Install a 0-60 or 0-100 psi fuel pressure gauge to adapter tool 6976 (Figure 2).
7. Start and warm engine and record fuel pressure. Pressure should be 117-152 kPa (17-22 psi) at idle speed. A minimum of 172 kPa (25 psi) should be indicated after raising engine speed to its rated rpm (2,500 rpm) with no load.
8. If supply pressure is less than 17 psi at idle or 25 psi at 2500 rpm (no load), restrict the fuel return hose by pinching the hose (Figure 3). If pressure returns to normal or above, replace the overflow valve with a new valve (P/N 04883838AA). The overflow valve is located on the side of the injection pump (Figure 4).
NOTE: High pressure at idle indicates that there is a restriction. Make sure that the overflow valve is located at the pump outlet, not the pump inlet (Figure 4).
a. To install the new overflow valve, remove the overflow valve from the pump. A clean lint free rag should be placed beneath the valve to catch excess fuel. Install the new valve and torque the valve to 24 Nm (18 ft. lbs).
NOTE: ALWAYS USE NEW RUBBER COATED SEALING WASHERS (PIN 4761245) WHEN REPLACING THE OVERFLOW VALVE.
9. If the supply pressure remains low with the return line restricted, check for inlet restrictions between the tank and the injection pump (such as pinched fuel lines, dirty pre-filter, and/or primary filter, etc.). If no inlet restriction is found, a faulty fuel transfer/lift pump is indicated. Refer to the 1996 Ram Truck Service Manual (Publication No. 81-370-6108), page 14-107 and 14-108, for information regarding fuel transfer/lift pump removal and installation procedures.
10. Fuel supply pressure should be checked after every corrective action. Refer to the 1996 Ram Truck Service Manual (Publication No. 81-370-6108), page 9-14 through 9-20, for further information regarding diesel engine performance testing.
NOTE: WHENEVER THE FUEL INJECTION PUMP IS REPLACED OR REMOVED FOR CALIBRATION, USE NEW RUBBER COATED SEALING WASHERS (PIN 4761245) ON THE INLET FUEL LINES AND ON THE OVERFLOW VALVE. ALSO, MAKE SURE A NEW OVERFLOW VALVE (PIN 4883838AA) IS INSTALLED WITH THE INSTALLATION OF A NEW FUEL INJECTION PUMP. THE ORIGINAL OVERFLOW VALVE MUST STAY WITH THE ORIGINAL INJECTION PUMP.
Policy: Information Only
Thanks to Bob Bergevin and Barry Drodge for supplying this TSB information
This page was edited on: May 3, 2004