1999/08/17 Caterpillar

Caterpillar Machines Powered by 3408E (99C) and 3412E (80M) Engines

There are several possible causes for 3408E and 3412E Engines that are difficult to start or will not start, or engines that will start but will not continue to run. Refer to the service manual for mechanical and electronic troubleshooting information and procedures.

Perform the following checks:

1. Visually check the fuel level and oil level. Verify minimum fuel and oil pressures.

2. Check for correct installation of the Electronic Control Module (ECM) connectors, speed/timing sensor connector, and the unit injector connectors. Verify that the ECM is receiving the correct voltage.

3. Check the injection actuation pressure control valve seals.

4. Use Electronic Technician (ET) to check for faults and logged events. While the engine is cranking, observe the engine speed to verify that the speed/timing sensor circuit is operating correctly. Verify that actual injection actuation pressure and current are normal.

Also refer to Power Connection Broadcast video and handouts for January 1999 (LEVN4568).

Since the 3408E and 3412E fuel injectors are actuated by oil pressure, the Injection Actuation Pressure System could be one possible cause. To begin troubleshooting a 3408E or 3412E Engine that is hard to start or starts and dies, compare the actual and desired injection actuation pressures while the engine is cranking. The actual and the desired injection actuation pressures should be approximately the same value. Some fluctuation in the actual injection actuation pressure is normal. If the fluctuation is extreme, there may be a possible problem with the compensator control valve or the hydraulic pump. A customized ET screen like this one is helpful for checking the Injection Actuation Pressure System.

An optional parameter for this screen would be the engine oil temperature.

Here are four possible situations that would not allow the engine to start or to start but not run properly:

Injection Actuation Current is 100% and Actual Injection Actuation Pressure is Low

If the injection actuation current is at 100% and the actual injection actuation pressure is low, there is possibly a leak in the injector or the jumper tube that provides the oil to the injector. The minimum pressure required to enable the injector is approximately 4500 kPa (650 psi) and the normal operating range is 5000 to 21 000 kPa (725 to 3100 psi). The pressure must be 5000 kPa (725 psi) for the engine to start. 1800 kPa (260 psi) is the default value for the sensor.

When inspecting the engine for oil leaks, first check the engine when it is cold by just cranking and not allowing the engine to start. If there are no visible leaks, then run the engine (if it will start) until it reaches operating temperature. Leaks will be much more visible when the oil is warm and under pressure.

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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact the skin.

First remove the valve covers and disable all unit injectors using an ET service tool, ground level shutdown switch, or by disconnecting the injector wiring in the valve cover base. Then crank the engine and observe each injector and the joints where it connects to the jumper tube. Also check the spill port, which is on the top of older injectors and on the bottom of newer injectors. An oil drip is acceptable, but a pencil-sized flow would be considered a large leak and could prevent the engine from starting. If an injector is leaking from the spill port, the injector should be replaced. If there is a massive leak in the joint between the jumper tube and the manifold, remove the jumper tube, check the seals and replace any seals that are damaged. Then reinstall the jumper tube and torque the bolts. Refer to Special Instruction REHS0116-02 for the complete procedures, specifications and the tools required for removing and installing injectors.

Injection Actuation Current is 100% and Actual Injection Actuation Pressure Is Normal

If the injection actuation current is at 60% to 100% and the injection actuation pressure is normal, there may be a small leak, which is large enough to cause the engine to not run properly. The leak can be made more apparent by performing the injection actuation pressure override test, which will raise the injection actuation pressure.

The engine should be at operation temperature before starting the test. This will make a small leak more obvious. Disable both injectors under the valve cover where you suspect the leak may be and run the engine. Using ET, increase the desired injection actuation pressure incrementally to the maximum vale of approximately 3300 psi. Observe the injectors, the jumper tube connections and the injector spill ports to identify the source of the leak. When the source of the leak is identified, use the repair procedures mentioned in Injection Actuation Current is 100% and Actual Injection Actuation Pressure is Low.

Injection Actuation Current is Normal (20%-50%) and Actual Injection Actuation Pressure is Low

If the injection actuation current is normal (20%-50%) and the actual injection actuation pressure is low, the screw in the compensator control valve may have backed out. On older pumps a compensator plug can be installed to correct this situation. Refer to Special Instruction REHS0282-01 for the installation procedure for the appropriate length compensator standby plug from the 161-8627 Plug Kit. Another item to check is the injection actuation pressure control valve for proper operation. The 166-5985 Pump Compensator is also a serviceable part. Refer to Service Magazine; "Compensator and Socket Head Bolts For 3408E and 3412E Hydraulically Actuated Electronically Controlled Unit Injector (HEUI) Hydraulic Pump Now Available"; November 16, 1998; Page 28-29.

Air In Fuel System

A loose injector can allow combustion gas to leak into the fuel system and cause the engine to misfire. If the base of the injector does not seal against the bottom of the injector sleeve, combustion gas can leak into the body of the injector and then into the fuel. The following method can be used to check for air in the system. With the engine running, grasp the fuel return lines at the rear of the engine. Air in the fuel system will cause pressure pulsations in the return hoses. The hoses will expand and contract with each pressure spike. If one hose has higher spikes than the other does, this is a good indication that the corresponding cylinder bank has the loose injector. The other injectors downstream from the loose injector will probably also misfire. Verify that the clamps holding the injectors are torqued to 47 ± 9 N·m (35 ± 7 lb ft). Refer to Special Instruction REHS0116-02 for installation and torque procedures for the injector.

Remember these tips to avoid leaks associated with the injectors:

* Check for leaks when the engine is cold, and then check when the engine is at operating temperature.

* Leaks will be much more visible when the oil is warm and under pressure.

* Be sure each injector clamp is properly torqued.

* Replace the seals on all mating surfaces of the jumper tube.

* Use the correct torque sequence and specification on the jumper tube.

* Refer to Special Instruction REHS0116-02 for the correct injector removal and installation procedure.

Once the leak has been identified and repaired, verify the actual injection pressure and current.