Engine Performance - Diagnosing Hard Starting When Hot

Bulletin # 87-054

Section: Product

Dated: 11/09/87

Subject:
HARD STARTING WHEN HOT

TO: ALL RANGE ROVER DEALERS

When diagnosing hard starting problems when hot, fuel pressure check as part of your initial diagnosis.

The following procedures should be followed:

1. Depressurize Fuel System.

A. With the ignition off, remove fuel pump relay

B. Crank the engine for a few seconds - engine may start and run until fuel pressure is reduced.

C. Switch off the ignition.

D. Connect the fuel pressure gauge in the system supply side between the fuel line and fuel filter. See Workshop Manual section 19, p. 18, 19.

E. Reinstall the fuel pump relay.

2. Start engine and observe pressure.

A. With high manifold vacuum (at idle) gauge should indicate approximately 26 PSI.

B With low manifold vacuum (under load) pressure should rise to approximately 34-37 PSI.

C. Switch the ignition off. Fuel pressure should drop no more than a maximum of 10 PSI in one minute.

3. To isolate a loss of residual pressure perform the following check:

With the fuel pump running, pinch off the fuel return line (connected to the outlet of the pressure regulator) and IMMEDIATELY switch off the fuel pump (assistant required).

CAUTION:
To prevent damage to the fuel line, use locking pliers with rounded jaws designed for this purpose.

A. If the fuel pressure no longer decreases, the fuel pressure regulator should be replaced.

B. If the fuel pressure continues to decrease, suspect a faulty fuel pump check valve or leaking injector. Investigate the cause and correct.

CAUTION:
Depressurize fuel system before servicing.

4. Quality check the vehicle making sure the customers complaint of hard starting has been corrected. Operate the vehicle until normal operating temperature is reached. Turn ignition off and restart within 5 to 15 minutes.

Loss of residual fuel pressure is only one cause of hard starting when hot. Remember to check basic tune specs, i.e. ignition timing, spark plug gap, high tension wires, etc.

In addition, these checks should be performed as required:

1. Fuel quality i.e. octane, presence of alcohol or water.

2. Vacuum leaks.

3. Evaporative loss control system (ELC) integrity.

4. EFI System check.