Fuel Pump - Diagnostic Procedures

90isuzu04 BULLETIN NUMBER SB90-02-002
ISSUE DATE August 9, 1990
GROUP FUEL
FUEL PUMP REPLACEMENT (4ZE1 AND V6 ENGINES)

AFFECTED VEHICLES

1988-90 Trooper II (KT), Pickup (TF) and Amigo (TC) models with 4ZE1 or V6 engine.

SERVICE INFORMATION

Many fuel pumps that are replaced because of hard start condition are later found (during failed parts inspection) to have no defects.

This Service Bulletin describes basic diagnostic procedures which must be completed before a fuel pump is replaced.

SERVICE PROCEDURE

1. Verify that all engine electrical connections and ground points are properly secured.

2. Verify that all vacuum hoses are properly installed.

3. While cranking the engine, verify that battery voltage is present at the fuel pump red wire.
4. Verify that the fuel pump black wire is properly grounded.

5. If there is no battery voltage present at the red wire, refer to the appropriate Electrical Troubleshooting Manual for fuel system circuit diagrams and connector locations.

6. If battery voltage is present at the red wire, perform the fuel pressure test outlined in the Emissions section of the appropriate Workshop Manual.

7. If fuel pressure test is OK, the fuel pump is operating normally and does not require replacement.