Petrol injection system troubleshooting

Before using the troubleshooting chart to locate the fault, the following test requirements must be met: rule out operator error when starting. For both cold and warm engine: do not press the accelerator pedal during the starting procedure; depress the clutch pedal.

Fuel in tank, compression OK, battery charged, starter motor turns at sufficient speed, ignition system OK, no leaks in fuel system, contamination in fuel system ruled out, crankcase ventilation OK, electrical earth connection (engine-gearbox-body) present. Read fault memory (workshop work).

Caution: before disconnecting fuel lines, clean them with cold cleaner or petrol.

Fault	Cause	Remedy
Engine does not start.	Electric fuel pump does not run when the starter is operated (no running noise audible). Fuse faulty. Fuel pump relay faulty. Injectors receive no voltage.	Check whether voltage is present at the pump.

Check electrical contacts for good conductivity.

Check fuses for fuel pump/injection system.

Check relay.

Disconnect the plugs from the valves, connect a test lamp and operate the starter. The test lamp must flicker faintly. If the lamp glows faintly: replace the control unit; if the test lamp does not light: check the relay.

Cold engine is hard to start and runs roughly. Temperature sensor faulty.

• Check coolant/intake air temperature sensor.

The engine cuts out. Electrical connections to fuel pump intermittently interrupted.

Fuel delivery rate too low.

Fuel filter clogged.

Fuel pump faulty.

Injector faulty.

• Check plug connections and cable terminals on the fuel pump and the fuel pump relay for secure, low-resistance connection.

Check fuse and contact points on the fuel pump relay. Clean contacts or replace as necessary.

Replace.

Check fuel pump delivery rate.

Replace fuel filter.

Check fuel pump.

Check injectors.

The engine has transition problems. Air intake system leaking.

Temperature sensor faulty.

Fuel system leaking.

• Check the intake system. To do so, run the engine at idle and brush seals and connections in the intake tract with petrol.

If engine speed increases briefly, rectify the leak. Caution: petrol vapours are toxic, do not inhale!

Check coolant/intake air temperature sensor.

Visually inspect all connections in the area of the engine and the electric fuel pump.

Tighten all connections. The hot engine does not start. Fuel system pressure too high.

Return line between pressure regulator and tank blocked or kinked.

Note: newer engines have no return line.

• Have fuel pressure checked; replace pressure regulator if necessary.
• Clean or replace line.