Checking the fuel pump for proper operation, measuring fuel pressure (Honda Accord 6)

Warning! See warnings at the beginning of the Section Relieving pressure in the fuel system.

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.

General checks

1. Make sure there is enough fuel in the gas tank.

2. Make sure that the fuel pump is actually working. Ask an assistant to turn on the ignition by turning the key to the ON position - you should hear the characteristic sound of the pump working in the gas tank (the pump should work for about two seconds).

Note: The sound of the pump running can be heard clearly through the open fuel tank neck. If the pump does not turn on, proceed immediately to checking its electrical circuit.

Checking the pressure characteristic of the fuel pump

1. Remove the fuel pulsation damper (see Section Relieving pressure in the fuel system) and screw in its place the adapter for connecting the pressure gauge.


2. Without starting the engine, turn on the ignition. Make sure that the K/V is off. The fuel pump will turn on for a couple of seconds - the pressure in the fuel system should rise (check the pressure gauge reading) and stabilize.





3. Start the engine and warm it up at idle speed to normal operating temperature. Compare the pressure gauge reading with the requirements of the Specifications. Now disconnect the vacuum hose from the fuel pressure regulator - the pressure gauge reading should immediately rise, again to the value specified in the Specifications.



4. If the pressure does not increase when the vacuum hose is disconnected, use a hand vacuum pump to create a vacuum of 305÷355 mm Hg in the regulator. If the pressure now drops, check the proper functioning of the vacuum source, otherwise replace the regulator.



5. If the pressure measurement results are outside the acceptable range, perform the following checks:

• a) If the pressure is excessively high, check the vacuum regulator for proper supply. The vacuum depth should fluctuate with engine speed. If there is a vacuum, check the condition and blockage of the fuel return hose/tube. If the return line is OK, replace the regulator.
• b) If the pressure is excessively low, change the fuel filter, eliminating the possibility of its obstruction (the filter is built into the fuel pump/fuel flow sensor assembly and is removed together with the latter, - see Section Removal and installation the fuel pump). If replacing the filter does not help to correct the situation, install a shut-off valve in the section between the regulator and the return fuel line (instead of a valve, you can install a section of flexible hose that can be easily pinched with pliers or a clamp). Start the engine and begin to slowly close the valve / pinch the hose. If the pressure rises above 3.3 kgf / cm², replace the regulator (see Section Removal and installation the fuel pressure regulator). Caution: Do not allow the pressure to rise above 4.2 kgf/cm². Do not pinch the return fuel line itself to avoid the risk of damaging it.
• c) If the pressure remains excessively low even with the return line closed, check the injection injector(s) for leaks (see Section Removal and installation of fuel lines and fuel injectors). Also check the serviceability of the fuel pump.

6. After completing the check, release the pressure (see Section Relieving pressure in the fuel system) and disconnect the pressure gauge.

Checking the fuel pump electrical circuit

Note: For more detailed information on the fuel pump electrical circuit diagram, refer to Chapter On-board electrical equipment.

1. If the fuel pump does not operate when the ignition is turned on (no characteristic sounds are heard from the fuel tank), check the condition of the fuel pump fuse (No. 1) or the ACG S fuse (both 15 A) in the mounting block located in the engine compartment. If necessary, replace the blown fuse and repeat the check. If the pump starts to operate after replacing the fuse, check the wiring of its circuit for signs of a short circuit in the section between the PGM-FI relay and the pump.

Note. The models considered in this Manual are equipped with a special engine start permission circuit that supplies power to terminal No.2 of the main relay only when the clutch is depressed (manual transmission)/the selector lever of the automatic transmission is set to the "P" position. A special 7.5 A fuse provides protection of this circuit from overloads - check the condition of fuse No.13 in the mounting block in the engine compartment of the vehicle.

2. If replacing the fuses does not restore pump operation, check the condition of the main relay electrical circuit.

Note: The main relay is mounted on a bracket mounted under the vehicle's instrument panel, to the left of the steering column. Have an assistant cycle the ignition on and off several times and check for proper battery voltage supply to the relay connector (see accompanying illustration).

3. When the ignition is off, voltage should be present at terminal 7 of the connector. Voltage should be present at terminal 5 only when the ignition is on (do not start the engine), while terminal 2 should be supplied with power only when the clutch pedal is depressed (models with manual transmission)/the selector lever is moved to the "P" position.

4. If there is no voltage, check the condition of the circuit between the relay and the PCM, otherwise make sure that the relay itself is in good condition.



5. Connect the positive battery terminal to terminal 2 with a jumper wire, ground terminal 1. Use an ohmmeter to check for continuity between terminals 4 and 5. If there is no continuity, replace the relay.

6. Now apply battery power to terminal 5 of the relay, ground terminal 3. There should now be continuity between terminals 6 and 7, otherwise replace the relay.



7. If continuity is present, apply power to terminal 6, ground terminal 1 and check for continuity between terminals 4 and 5. If there is no continuity, replace the relay, otherwise check the circuit condition between the fuse, relay and pump.

8. If the above checks do not reveal the cause of the pump failure, check to see if the power supply to the fuel pump assembly in the gas tank is working properly. If the power supply is working properly, replace the fuel pump/flow sensor assembly (see Section Removal and installation the fuel pump).