- This is a pump that is activated when the engine is started via the fuel pump relay.
- The pump is equipped with a check valve that maintains pressure in the system when the ignition is off. This makes it easier to start the engine.
- A pressure absorber installed at the pump inlet to the pipeline prevents sudden pressure drops that can occur when starting the engine.
Fuel pump malfunctions
The fuel pump receives electricity through a relay installed in the engine compartment. Thus, the pump only works when the engine is running or when the ignition key is turned to the engine start position.
The second relay cuts off the power supply via a safety switch in the engine control unit if the engine stops running when the ignition is on, i.e. no more electrical impulses are sent to the control unit.
The safety switch prevents a fire from igniting the leaking gasoline in an accident. Therefore, troubleshooting the pump is quite difficult, and if the malfunction could not be found, as described below, then it is best to contact an auto repair shop. There is the necessary tester for the electronic engine control device, with which the fault can be quickly detected.
1. Turn off the ignition (see chapter Ignition system).
2. Disconnect the high pressure fuel lines from the pressure regulator (single point injection system) or distribution pipeline (multipoint injection system) - Keep a rag ready to avoid splashing gasoline.
3. Even with the engine off, a small amount of gasoline should leak out, as the fuel system is under pressure.
4. If gasoline does not flow out, have an assistant turn the key to turn on the ignition (but no starter!).
5. If gasoline does not flow, check the pump fuse or relay.
6. With a good relay and, accordingly, a good fuse, check if the pump itself is working: ask an assistant to turn on the ignition and listen if the pump is noisy.
7. If the fuse is defective, replace it.
8. If the pump has started, then you must find the cause of the defective fuse.
9. After removing the trunk cover, lightly tap on the pump housing, this sometimes helps. If the pump was slightly blocked, it will work again.
10. Is the electrical wire connector on the pump well secured?
11. If the pump still does not work, check with a diode voltage indicator (a conventional test lamp will not work here, as the ignition control device can be damaged), whether there is current in the circuit. At the same time, turn on the ignition.
12. If there is voltage, the pump may be faulty or the wire may be broken.
13. If the pump runs but no fuel flows to the pressure regulator, the fuel filter or hose is clogged or the fuel line is bent.
14. If, after all the checks, the pump does not work, it remains only to remove the tank in order to check the pump itself and, if necessary, replace it.
Checking the amount of fuel pumped by the pump
If the engine does not develop sufficient power at high speeds or «chokes» when driving evenly, this may be caused by insufficient amount of fuel that the pump pumps. In this case, it is necessary to check the amount of fuel supplied by the fuel pump.
1. Remove the fuel line from the pressure regulator to the injection system and plug it with a suitable screw.
2. Attach the replacement hose to the pressure regulator and have an assistant lower it into a measuring container.
3. Remove the fuel pump relay from its location in the engine compartment and short terminals #3 and #5.
4. With a battery voltage of 12 V, the pump should pump 830 cm3 after running for one minute with a single-point injection system3, with a multi-point injection system - more than 1000 cm 3 of fuel.
5. If too little fuel is being pumped, then measure the voltage of the storage battery and, if necessary, replace the fuel filter and measure the amount of fuel pumped again.
6. If an insufficient amount of fuel is injected again, then replace the fuel pump.
In case of insufficient fuel supply, remove the hose clamp (4) and a fuel tank pump. Disconnect wires first (2 and 3), and a hose (1).
Removing the fuel pump
If the electric fuel pump is faulty, it must be replaced as it cannot be repaired.
1. Remove the tank as described.
2. Remove the thrust ring with a spanner or two screwdrivers (note: left hand thread).
3. Replace the fuel pump flange gasket, as it is damaged when the pump is removed and therefore cannot be reinstalled.
4. Before installing the fuel pump, clean the receiving mesh, and also clean all contact surfaces of the tank and pump.
5. Before putting on the fuel and ventilation hoses, clean all pump connections.