Fuel System Diagnosis
EARLY MODEL VEHICLESNOTE: The following test procedures assume that the ignition system is functioning, and that a good spark is evident at the plugs. Ensure that this is the case prior to proceeding with fuel system diagnosis.
Fuel Injector Connector:
1. Loosen fuel tank filler cap to relieve fuel tank pressure. Disconnect injector wiring at an injector and connect a jumper wire from terminal #1 of the injector harness to ground. Connect a second jumper wire to terminal #2, and touch the battery positive post for no more than 5 seconds. System pressure is now released.
2. Disconnect the fuel supply hose from the fuel rail, and install fuel line adaptor, tool number 6175 or equivalent.
3. Connect fuel system pressure gauge with a range of 0-60 psi to the adaptor.
4. Place ignition switch in RUN position to activate fuel pump and pressurize system. If fuel pump fails to actuate, check fuel pump relay operation. Testing and Inspection
5. After actuating fuel pump the gauge should read 28-30 psi (193-207 kPa).
^ If fuel pressure is below specification proceed to step 6.
^ If fuel pressure is above specification proceed to step 7.
^ If fuel pressure is within specifications, and vehicle has a driveability problem check injector operation. 6. If fuel pressure is below specification, move pressure gauge to fuel supply line and install between fuel tank and fuel filter. Repeat test procedure, and check fuel system pressure. If pressure is 5 psi higher than previous reading and within specification, replace fuel filter. If no change occurs in pressure, gently squeeze fuel return hose. If pressure increases to specification, replace fuel pressure regulator. If no change in pressure occurs, the fuel pump is defective and must be replaced.
7. If fuel pressure is above 394 kPa (57 psi) remove fuel return hose from fuel pressure regulator end, and install a suitable hose from fuel pressure regulator output. Place the other end of the hose in a clean and approved container. START engine and observe fuel pressure. If pressure is now within specification, problem is a restriction in fuel return line, or an obstructed fuel return check valve in tank. Clear return line obstruction if necessary, and or replace fuel tank assembly if in-tank check valve is obstructed. If pressure is still above specification replace fuel pressure regulator.
LATE MODEL VEHICLES
NOTE: The following test procedures assume that the ignition system is functioning, and that a good spark is evident at the plugs. Ensure that this is the case prior to proceeding with fuel system diagnosis.
Fuel Injector Connector:
1. Loosen fuel tank filler cap to relieve fuel tank pressure. Disconnect injector wiring at an injector and connect a jumper wire from terminal #1 of the injector harness to ground. Connect a second jumper wire to terminal #2, and touch the battery positive post for no more than 5 seconds. System pressure is now released.
2. Disconnect the fuel supply hose from the fuel rail, and install fuel line adaptor, tool number 6175 or equivalent.
Fuel Line Disconnect Tool 6182:
Using Fuel Tube Disconnect Tool No. 6182:
3. Connect fuel system pressure gauge with a range of 0-60 psi to the adaptor.
4. Place ignition switch in RUN position to activate fuel pump and pressurize system. If fuel pump fails to actuate, check fuel pump relay operation. Testing and Inspection
5. After actuating fuel pump the gauge should read 43 psi (300 kPa).
^ If fuel pressure is below specification proceed to step 6.
^ If fuel pressure is above specification proceed to step 7.
^ If pressure is within specified limits problem is injector related.
6. If fuel pressure is below specification, move pressure gauge to fuel supply line and install between fuel tank and fuel filter. Repeat test procedure, and check fuel system pressure. If pressure is 5 psi higher than previous reading and within specification, replace fuel filter. If no change occurs in pressure, gently squeeze fuel return hose. If pressure increases to specification, replace fuel pressure regulator. If no change in pressure occurs, the fuel pump is defective and must be replaced.
7. If fuel pressure is above 43 psi (300 kPa) remove fuel return hose from fuel pressure regulator end, and install a suitable hose from fuel pressure regulator output. Place the other end of the hose in a clean and approved container. START engine and observe fuel pressure. If pressure is now within specification, problem is a restriction in fuel return line, or an obstructed fuel return check valve in tank. Clear return line obstruction if necessary, and or replace fuel tank assembly if in-tank check valve is obstructed. If pressure is still above specification replace fuel pressure regulator.