Oil Rail Cleaning Procedure For the C7 Engine
C7 Cylinder Head
The oil and fuel passages are the same for both the C7 and C9.
(6) Oil Rail for a HEUI fuel system
(7) Oil passage to injector bore
(8) Fuel passage
(9) Injector bore
Note: Contain any oil and cleaner that will flow from the cylinder and the lines during the following process. Properly dispose of the oil and contaminated cleaner when work is complete.
- Remove fuel injectors. Refer to Disassembly and Assembly for specific machine.
- Install six plugs 9U-7080 Tapered Cap/Plug into the lower injector bores. The plugs will prevent oil, cleaners, and debris from entering the cylinders.
- Remove the plugs from the front and rear of the cylinder head main oil gallery
- Remove the pressure sensor from the cylinder head. Protect the sensor.
- Clean out the two rail drain holes by removing their plugs and using the brake cleaner and long squirting straw to flush these passages to the oil rail.
- Using the solvent gun with and without the air hose extension blast mineral spirits into the rail, washing debris down to the injector bores. Using a drop light shining into the injector bores from above will allow monitoring of how much fluid is collecting in the tapered plugs.
- When the plugs in the injector bores become full use the shop vacuum with decreasing diameter tubing attached to suck out each injector bore.
- Continue to repeat steps 6 and 7, squirting the solvent gun into the rail through every hole possible, including the front and rear main gallery plug holes, the sensor hole, and the pump inlet hole. Using the air hose extension on the solvent gun will allow the solvent to be directed more towards one injector hole than the others. Monitor accumulation of dirty solvent in the cups while spraying solvent.
- Clean rail until the fluid collecting in the tapered plugs has no more metallic debris. Once the oil is washed from the rail the runoff fluid collecting in the plugs will be clear but still contain debris. Inspect with a drop light to ensure the absence of any shiny particles.
- Once the rail is clean use the brake cleaner and long spraying straw in the injector bores to backflush the passages from the injector bores to the rail.
- Using the brake cleaner and long spraying straw in the injector bores flush out the fuel passages between the injector bores.
- Using the shop vacuum, suck out the brake cleaner and debris from the injector bores.
- Using the solvent gun blow out rail from front to back. Finish up with spraying just air. If rear plug cannot be removed, solvent will have to be sprayed in and then sucked out with the shop vacuum.
- Using a drop light and small mirror inspect entire rail for debris. If any is found repeat cleaning procedure until rail is completely clean of debris.
- Double check fluid in caps has no debris, suck out fluid, remove caps, suck out cylinders.
- Clean and reassemble the oil filter bypass valve.
- Refer to Truck Engine News, SEBD6764, “A New Spring for the Oil Filter Bypass Valve and for the Oil Cooler Bypass Valve is Now in Production”, Service Magazine, SEPD0718, “A New Spring for the Oil Filter Bypass Valve and for the Oil Cooler Bypass Valve is Now in Production” and Engine News, SEBD9329, “A New Spring for the Oil Filter Bypass Valve and for the Oil Cooler Bypass Valve is Now in Production” for the correct selection of the springs for the bypass relief valve and the oil cooler.
- Reassemble engine, using replacement HEUI Pump and Injectors.
- Replace the engine oil and the oil filter. Refer to the Operation and Maintenance Manual for your specific machine to determine refill capacity.