Honda Civic. Manual — part 674

Special Tools Required

Vacuum pump/gauge, 0-30 in.Hg, Snap-on YA4000A or equivalent, commercially
available

Check for a gas leak if there is an odor coming from the vehicle. Compressed
natural gas (CNG) can only be smelled, not seen.

1. Open the hood and the fuel fill door.
2. Connect a vacuum pump/gauge, 0-30 in.Hg, to the hose (A) from fuel pressure

regulator P1, and apply 67.7 kPa (20 in.Hg, 508 mmHg) of vacuum.

Fig. 69: Identifying Hose

3. If fuel pressure regulator P2 does not hold vacuum, replace it before continuing

to the next step.

4. Inspect the fuel lines and hoses under the hood for kinks, abrasion, and other

signs of damage.

5. With the manual shut-off valve open, turn the ignition switch ON (II), but do

not start the engine. After the fuel pressure regulator shut-off solenoid
valve/fuel tank internal solenoid valve operates for about 2 seconds, the fuel

WARNING:

Compressed natural gas is flammable and highly
explosive. You could be killed or seriously injured if
leaking natural gas is ignited.
Stop the engine, and keep heat, sparks and flames
away.

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Fuel Supply System - Civic GX

pressure in the fuel lines rises. Turn the ignition switch OFF. Repeat this two
or three times.

6. Within 1 minute, check for any damaged lines with a leak detector (A)

(Matheson Leak Hunter Plus, model number 8066 or Snoop Soap Suds (B)).

Fig. 70: Identifying Leak Detector And Snoop Soap Suds

7. If no damage was noticed during the inspection, turn the ignition switch ON

(II) for 2 seconds, then turn the ignition switch OFF. Within 1 minute, check
for a leak at the vent hose outlet inside the fuel pipe protector (A).

Fig. 71: Identifying Fuel Pipe Protector

8. If you detect a leak, remove the vent hose, and check the fuel lines and fittings

at the solenoid valve with a leak detector.

9. If you cannot find the leak, raise the vehicle on a hoist, remove the under-floor

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Fuel Supply System - Civic GX

cover, and inspect all the fuel lines under the vehicle visually and with a leak
detector.

10. If you still cannot find the leak, remove the rear seat, and check all fuel lines

and fittings at the fuel tank and the fuel joint block.

FUEL PRESSURE RELIEVING

This procedure should be done outside in a well-ventilated area or in a properly
equipped CNG shop.

BETWEEN THE ENGINE AND THE MANUAL SHUT-OFF VALVE

This procedure will allow you to safely work on any part of the fuel system
downstream of the manual shut-off valve, such as fuel pressure regulator P1 or the
fuel injectors.

1. Lift the vehicle, and support it with jackstands.
2. Close the manual shut-off valve (A).

Fig. 72: Identifying Manual Shut-Off Valve

3. Start the engine, and let it idle. After a few minutes, the engine will stall.

WARNING:

Compressed natural gas is flammable and highly
explosive. You could be killed or seriously injured if
leaking natural gas is ignited.
Stop the engine, and keep heat, sparks and flames
away.

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Fuel Supply System - Civic GX

4. Turn the ignition switch OFF.

BETWEEN THE FUEL TANK AND THE ENGINE

This procedure will allow you to safely work on any part of the fuel system
downstream of the fuel tank such as the fuel joint block or the manual shut-off
valve.

1. Remove the rear seat (see REAR SEAT REMOVAL/INSTALLATION ).
2. Disconnect the fuel subharness 6P connector (A) (this prevents the tank from

supplying fuel to the system).

Fig. 73: Identifying Fuel Subharness 6P Connector

3. Start the engine, and let it idle. After a few minutes, the engine will stall.
4. Turn the ignition switch OFF.

BETWEEN THE FUEL RECEPTACLE AND THE FUEL TANK

This procedure will allow you to safely work on any part of the fuel system between
the fuel joint block and fuel receptacle.

1. Relieve the fuel pressure between the fuel tank and the manual shut-off valve

(see the previous procedure).

2. Remove the under floor cover (A).

NOTE:

Make sure the manual shut-off valve is open.

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Fuel Supply System - Civic GX