Fuel System Diagnosis

NOTE: The following test procedures assume that the ignition system is functioning, and that a good spark is present at the spark plugs. If this is not the case repair the ignition system before proceeding.

NOTE: If engine starts but has a driveability problem go to step 3.

1. Remove air cleaner housing, disconnect coil wire from distributor and ground the loose end of wire.
2. Observe the fuel injector while cranking the engine for at least 7 seconds.
- If a normal amount of fuel is being sprayed by the injector, and there is a good spark but the engine does not start, check valve timing as timing belt may have slipped.
- If no fuel is being sprayed by the injector, go to step 3.

Testing Fuel Pressure:

3. Remove the plug from the pressure test port on the throttle body.
4. Install a pressure test fitting in place of the plug, and connect a 0-207 kPa (0-30 psi) fuel pressure gauge to the test fitting.
5. Turn the ignition key ON and observe the fuel pressure gauge. The fuel pump should engage for approximately 2 seconds, (listen for a hum coming from inside the fuel tank), and build fuel pressure to approximately 97-103 kPa (14-15 psi).
- If fuel pump fails to engage, (no pressure is observed and no hum is heard), test the fuel pump relay operation.
- If fuel pressure is below 93 kPa (13.5 psi) proceed to step 6.
- If fuel pressure is above 111 kPa (16.0 psi) proceed to step 8.
- If pressure is as specified and there was no fuel spray during cranking the problem is injector related. Check the fuel injector electrical circuit.
6. If fuel pressure is below specification, gently squeeze the fuel return hose.
- If the pressure increases to specification or higher, release the fuel return hose and adjust fuel pressure.
- If fuel pressure fails to increase to specification go to step 7.
7. Remove pressure gauge from throttle body fuel supply line and install gauge 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 in pressure occurs, replace the in tank pump and sock type filter.
8. If fuel pressure is above 111 kPa (16.0 psi), adjust pressure regulator.
9. If fuel pressure cannot be adjusted to specification, 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 large (2 gallon minimum), clean container, approved for this purpose. 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.