Fuel Pump: Testing and Inspection
FUEL PRESSURE AND RESIDUAL PRESSURE CHECK
Checking the Pressure Regulator Vacuum Hose
^ Remove the vacuum hose from the pressure regulator.
^ Check that the hose is not blocked by blowing into it.
If the hose is OK:
- Connect the fuel pressure gauge.
If the hose is blocked:
- Check hoses and nipples and remedy the fault.
CONNECTING THE FUEL PRESSURE GAUGE
Fuel Pumps, Line And Pressure Regulator:
Engine Without Quick Connector
^ Switch Ignition OFF.
^ Connect the fuel pressure gauge between the fuel line and the distributor pipe. Use hose 5116 and nipple 5265.
^ Plug the free end of the meter's hose with plug 5266.
^ Set the valve on 5011 to position 1 (pointing towards hose 5116).
^ Continue to Starting Fuel Pump section below.
Engines With Quick Connectors
^ Connect nipple 9725 and adapter 5479 to the pressure gauge.
^ Plug the free end of the pressure gauge hose using a 5266 plug.
^ Connect the adapter to the valve on the distributor pipe.
^ Continue with Starting Fuel Pump section below.
Starting Fuel Pump
^ Lift out the central electrical module and remove the system relay.
^ Connect a wire between terminals 30 and 87/2 on the relay board. The Fuel Pump should now START.
^ Continue to Measuring System Pressure.
CAUTION: Jump connecting between the wrong terminals will destroy the LH control module.
Measuring System Pressure
^ Read the system pressure on the pressure gauge.
The system pressure should be 300 kPa (43 psi).
If the system pressure is too low:
- Proceed to: System Pressure Too Low section below.
If the system pressure is too high:
- Proceed to: System Pressure Too High section below.
If the system pressure is normal:
- Proceed to: Checking the Pressure Regulator section below.
System Pressure Too Low
^ Pinch the return lead and check to see if pressure rises.
Important: Do not let pressure exceed 600 kPa (85 psi).
If the pressure rises quickly:
- The pump and pipes are OK.
- Try using a new pressure regulator.
- Check that system pressure is normal.
- To disconnect, continue to Disconnecting Pressure Gauge.
If pressure rises slowly:
- Check the fuel filter, tank pump strainer and fuel line for blockages.
- Check that system pressure is normal.
- To disconnect, continue to Disconnecting Pressure Gauge.
If pressure does not rise:
- Try using a new Fuel Pump.
- Check that system pressure is normal.
- To disconnect, continue to Disconnecting Pressure Gauge.
System Pressure Too High
^ Switch ignition OFF.
^ Remove the wire from the Fuel Pump relay board.
^ Remove the return line from the pressure regulator. Blow into the line.
If the line is OK:
- Try using a new pressure regulator.
- Check that system pressure is normal.
- To disconnect, continue with Disconnecting Pressure Gauge.
If the line is blocked:
- Check the line for pinching and clogging.
- Check that system pressure is normal.
- To disconnect, continue with Disconnecting Pressure Gauge.
Checking Pressure Regulator:
Checking the Pressure Regulator
^ Connect a vacuum pump to the pressure regulator. Use vacuum pump 5843 for example.
^ Pump the air out of the regulator.
^ Check that system pressure decreases as much as the pressure in the regulator.
300 kPa (43 psi) - partial vacuum = system pressure.
^ Disconnect the hose from the vacuum pump.
^ System pressure should return to 300 kPa (43 psi).
^ Continue with Stopping the Fuel Pump.
Stopping the Fuel Pump
^ Remove the wire between the relay board terminals 30 and 87/2.
^ Reinstall the relay.
^ Continue with Checking Residual Pressure.
Checking Residual Pressure
^ Pressure must not sink below:
200 kPa (28 psi) in less than 20 minutes.
If residual pressure is OK:
- Proceed to: Disconnecting Pressure Gauge.
If pressure decreases too quickly:
- Check that the injectors or cold start valve are not leaking fuel.
If the valves are OK:
- Try using a new pressure regulator.
- Proceed to: Disconnecting Pressure Gauge.
Disconnecting Pressure Gauge
^ Switch Ignition OFF.
^ Hold a shop rag under the fuel line to absorb fuel that runs out when the pressure gauge is disconnected.
Important: Plastic fuel line ties which were removed must be replaced.