Fuel system — troubleshooting (Opel Ascona C)

Excessive fuel consumption and poor engine performance are not necessarily the result of a faulty fuel system. Exactly the same symptoms may indicate a faulty or poorly adjusted ignition system. Even if the problem really lies in the fuel system, you will have a hard time identifying it if the ignition system is poorly adjusted. The following diagnostics are based on the fact that you have already checked and adjusted the ignition system.

Part A: Carburetor Engines

Symptom/ Cause(s)

Smell of gasoline when turning off the engine/

• Fuel lines or fittings are leaking
• The fuel tank is leaking.

Gasoline smell when engine is idling/

• The fuel line fittings between the pump and the carburetor are leaking
• Fuel is overflowing from the float chamber due to an incorrectly adjusted level, a faulty needle valve or a leaking float.

Excessive fuel consumption due to reasons not related to leaks or the float chamber/

• The jets are worn out
• Too rich mixture
• One of the carburetor mechanisms is jammed
• The air filter is dirty
• The thermostat mechanism of the air purifier is jammed.

Problems with starting the engine, rough running, low engine power, spontaneous shutdown/

• One or more jets are completely or partially clogged
• The fuel level in the float chamber is too low or the needle valve is sticking
• Fuel pump not delivering enough fuel Solenoid shut-off valve defective (if installed)
• The induction system sucks in air
• The mesh filter on the carburetor fuel inlet line is clogged.

Problems with starting a cold engine/

• Manual or automatic suction is poorly adjusted
• The automatic choke was not reset before starting the engine.

Problems with starting a warm engine/

• Automatic choke is poorly adjusted
• The gas pedal was pressed several times before starting the engine
• Steam lock (especially likely in hot weather or at high altitudes).

The engine responds poorly to pressing the brake pedal/

• The accelerator pump is faulty
• The jet(s) is clogged
• The throttle cable is loose.

Idle speed drops when engine is warm/

• The temperature compensator is faulty
• The fuel pump overheated.

Part B: Injection Engines

Symptom/ Cause(s)

Problems with starting a cold engine/

• The fuel pump is faulty
• The fuel line or filter is clogged
• The auxiliary air valve is faulty
• The temperature sensor is faulty
• The vacuum system is leaking.

Problems with starting a warm engine/

• The air filter is clogged
• The fuel pump is faulty
• The vacuum system is leaking.

Excessive fuel consumption/

• Excessive fuel pressure
• The temperature sensor is faulty
• The air flow sensor is faulty
• The vacuum system is leaking.

Rough idle /

• The air intake system is leaking air
• The mixture composition is incorrectly adjusted
• The throttle switch is poorly adjusted
• The plug of the electronic control unit has come off
• The injector(s) is leaking.

Poorly regulated (too high) idle speed/

• The auxiliary air valve does not close.