12b. Combustion Gas In the Fuel Rail Test - Balloon Test

12b. Combustion Gas In The Fuel Rail Test Balloon Test

Purpose:

The purpose of this test is to check if any combustion gas leaks past the injector's needle and seat or past the copper combustion gasket.






Carry out the Combustion Gas In The Fuel Rail Test to verify the repair.

When the repair is verified carry out the Fuel System Delivery test in this section.

Recommended Procedure:

Note: The bubble test is used as a screening test prior to carrying out the balloon test. Depending on the leak rate bubbles in the secondary fuel filter bowl can be present even with all glow plugs removed.

Note: If injectors have been removed or the high pressure oil system repaired~ it may be necessary to operate the vehicle and carry out at least 12 short high demand acceleration cycles to purge air from the oil system.

^ If the bubble test indicated that combustion gas is leaking into the fuel system disconnect both fuel lines from the secondary fuel filter.
^ Install a latex balloon over each fuel line and secure with a tie strap.
^ Disconnect the fuel injection control module (FICM) relay.
^ Crank the engine and observe the latex balloons for compression pulses. Identify which bank is a cause of the concern.
^ To isolate multiple combustion gas leaks remove all but 1 glow plug from the bank that leaks the combustion gas in the rail. Crank the engine and observe the latex balloon for compression pulses. Repeat to isolate the leak.
^ For cylinders that leak combustion gas into the fuel rail remove the injector and inspect the lower 0-ring and copper gasket for an even circular crush pattern.

If a combustion gas leak is verified install new injectors as necessary.

If an even circular crush pattern is visible on the copper gasket install a new injector. Refer to Fuel Charging and Controls. Carry out the Combustion Gas In The Fuel Rail Test to verify the repair. When the repair is verified carry out the Fuel System Delivery test in this section.

If the copper gasket is missing and burnt away the lower 0-ring is damaged or the injector is loose install a new fuel injector and fuel injector hold down assembly. The most likely cause of a burnt or missing copper gasket is incorrect torque of the hold down assembly. Refer to Fuel Charging and Controls. Carry out the Combustion Gas In The Fuel Rail Test to verify the repair. When the repair is verified carry out the Fuel System Delivery test in this section.

Possible Causes:

^ Fuel injector
^ Fuel injector lower 0-ring
^ Fuel injector copper gasket

Tools Required:

^ latex balloons
^ tie straps