High Oil Consumption Caterpillar

High Oil Consumption

Usage:

3126B (7AS) TRUCK ENGINES

Problem:

Some 3126B HEUI Truck Engines may have excessive oil consumption as a result of oil leaking past an internal injector O-ring seal or as a result of a cracked or porous cylinder head. There may be no traditional signs (smoke, high blowby, etc.) of high oil consumption, but the fuel in the fuel tank may turn black.

To determine if oil consumption is excessive using either of the following criteria:

A. Oil consumption has doubled or tripled over a short period of time from the historical oil usage of the engine in question.

B. Oil consumption is 2 to 3 times that of other engines in similar applications.

Solution:

There are other reasons for black fuel, but if black fuel occurs with high oil consumption, there is usually a problem with the injectors, damaged injector O-ring seals, or cylinder head porosity or cracks. Use the following procedure for complaints of high internal oil consumption and/or black fuel.

1. Check for external oil leakage. If OK, proceed to Step 2.

2. Look for oil in the fuel tank. The fuel may be black. Proceed.

3. Remove the fuel injectors and check the injector O-ring seals for damage. Also check the injector bores in the cylinder head for scratches or damage. If this is not OK, this is the likely cause. Repair as required. If this is OK, proceed.

4. Install a known good set of injectors (new or remanufactured) with new O-ring seals. Use the correct tooling and installation procedures as shown in Special Instruction, REHS0184, "Removal and Installation Instructions for 3126B HEUI Injectors".

5. Pressure check the cylinder head using the following procedure:

A. Remove the fuel return line at the back of the cylinder head and plug the port.

B. Remove the fuel supply line from the front of the cylinder head and install an air tight valve and pressure gauge.

C. Pressurize the cylinder head with compressed air to approximately 690 kPa (100 psi). Check fitting for leaks with a liquid leak detector. Seal as necessary.

D. While monitoring the pressure gauge (from Step 5-B), close the air tight valve (from Step 5-B). Record the rate of pressure drop. Repeat the Step several times.

E. Rapid loss of pressure (MORE then 70 kPa (10 psi) per minute) indicates a porous or cracked cylinder head. Replace cracked or porous cylinder heads. If the pressure loss is minimal, leave in the new or remanufactured injectors (from Step 4) and the repair is complete.

Please share this information with your TEPS Dealers.

THANKS very much for your help in tracking and resolving this condition.