Attention! See the warnings at the beginning of the Section Depressurizing the supply system.
General Checks
Make sure there is enough fuel in the gas tank. Inspect fuel lines for signs of leaks.
Make sure the fuel pump is actually working. Engage the parking brake and ask an assistant to turn on the ignition by turning the key to the ON position - a characteristic sound of a running pump should be heard in the gas tank (the pump should run for about two seconds, during which the required pressure rise in the supply system is carried out).
Note. The sound of the running pump is clearly audible through the open neck of the fuel tank. If the pump is working properly, however, there are suspicions of a malfunction of the power supply system, measure the pressure developed by the pump.
If the pump does not turn on, proceed to check the condition of its electrical circuit (see chapter Onboard electrical equipment). Check the appropriate fuses and relays, make sure the power supply to the pump connector is good. Assess the quality of the ground.
If the power supply is correct and the grounding is not broken, replace the pump (see Section Removal and installation of the fuel pump).
Checking the pressure characteristic of the fuel pump
Note. To check the fuel pressure, you will need a special pressure gauge with a wide range scale and an adapter to connect the pressure gauge to the injection system.
1. Relieve the pressure in the supply system (see Section Depressurizing the supply system).
2. Disconnect the outlet line from the fuel filter, connect a three-way fitting between the filter and the fuel line, to which connect a pressure gauge. Track reliability of a tightening of hose collars.
3. Turn off all electrical consumers and turn the ignition key to the ON position. The fuel pump should turn on for 5 seconds - read the pressure gauge. Compare the result with the requirements of the Specifications.
4. Start the engine and warm it up at idle to normal operating temperature. Read the pressure gauge reading and compare it with the value given in the Specifications. Disconnect the vacuum line from the pressure regulator (see Section Removal and installation of the fuel pressure regulator), - the pressure must increase to the value specified in paragraph 4.
5. If the readings taken do not fall outside the allowable ranges specified in the Specifications, therefore, the system is functioning properly, otherwise, perform the following checks:
a) If the pressure is excessively high, check the vacuum supply to the fuel pressure regulator. A change in engine speed should lead to vacuum fluctuations. If vacuum occurs, check the patency and condition of the fuel return line hose and tube. If the return line is OK, replace the pressure regulator;
b) If the pressure is too low, check the condition and patency of the fuel filter and the fuel line going from the fuel line to the gas tank. If no abnormalities can be found during the inspection, start the engine and slowly clamp the return line. If the pressure rises above 3.0 kgf/cm2, replace pressure regulator (see Section Removal and installation of the fuel pressure regulator).
Attention! Do not allow pressure to rise above 4.2 kgf/cm2. If the pressure is still too low, replace the fuel pump (see Section Removal and installation of the fuel pump);
6. Shut off the engine, leaving the ignition on. Continue to watch the pressure gauge for about 5 more minutes - the pressure should decrease slowly. If the pressure drops excessively quickly, perform the following checks:
- a) Without turning off the ignition, pinch the fuel supply line in the area between the three-way fitting and the fuel tank, then turn off the ignition - if the pressure drops quickly, then there are leaks through the injector (s) injection;
- b) Switch on the ignition again and pinch the supply line, this time in the area between the fitting and the fuel line. Switch off the ignition - a rapid drop in pressure indicates a malfunction of the control valve of the submersible fuel pump.
7. When finished checking, relieve fuel pressure (see Section Depressurizing the supply system) and disconnect the pressure gauge.