Usage:
G333B, G333C, G342C, G353D, G379A, G398A, G399, G3304, G3306 Natural Gas Engines
- SUPPLEMENT: 10/12/81
SERVICE MAGAZINE, SEPTEMBER 21, 1981, PAGE 3. In the article "Preventive Maintenance For Natural Gas Engine Spark Ignition System," there is a four step procedure given which is used to check transformers. The information in steps two and three is only for solid state ignition systems.
For breaker point ignition systems, steps two and three must include the information that follows:
Measure the resistance between the positive and negative terminals. The correct indication is 5.7 to 6.3 ohms.
Measure the resistance between the high voltage tower and the negative terminal. The correct indication is 9975 to 11,025 ohms.
--------------- END SUPPLEMENT ---------------
Some Operation Guides do not give complete preventive maintenance information about spark ignition systems for the above engines. Preventive maintenance can prevent a failure that can cause the engine to run rough (misfire) or not run. A complete inspection of the spark ignition system must be part of the maintenance needed for your engine.
It is Caterpillar's recommendation that the preventive maintenance instructions that follow be used at each oil change interval for your engine.
These preventive maintenance instructions can also be used when troubleshooting the spark ignition system to find the cause of a failure. Correct troubleshooting procedures can prevent replacement of parts when not needed.
1. Check the connector of the wiring harness. It must be dry, clean and have a tight fit. If the connector is dirty or if any signs of corrosion are present, clean it with a freon solvent.
NOTE: Use of a freon solvent will cause the component that has been cleaned to be covered with a white sediment after the solvent is dry. Use a brush that has medium (between soft and hard) bristles to remove the sediment.
2. If the engine runs rough (misfires) or will not run, check the magneto. Special Instruction, Form GEG02059 has the information needed to check the magneto.
NOTE: Do not remove the magneto for diagnosis until after the ignition system has been completely checked.
1. Make an inspection of the primary wire harness. Make a replacement for the harness if any wires are broken, in compression (squeezed together or pinched) or have cracks in the insulation.
2. Inspect the ground wires in the same way as the primary wire harness. If any indication of a bad ground wire is present install a short wire between the negative terminal of the transformer (coil) and the transformer bracket assembly to make a good ground.
3. Check the terminals to the transformer. These terminals must be clean, free of corrosion and tight. Use ring terminals if a replacement must be made for any terminal.
4. Make a continuity check of all wires, especially when troubleshooting.
1. Inspect the brass connector in the high voltage tower of the transformers. If any paint, dirt or corrosion is present clean the connector with freon solvent or a fine grit abrasive material.
2. Use an ohmeter to measure the resistance between the positive and negative terminals. The correct indication is 0.3 to 0.6 ohms.
3. Measure the resistance between the high voltage tower and the negative terminal. The correct indication is 11,000 to 13,000 ohms.
NOTE: If any indication is outside of the correct indication make a replacement for the transformer.
4. Check the nuts on the primary terminals. If loose, tighten the nuts. Use double nuts (one above the other) to prevent loose connections.
1. Inspect all high tension wires. Make a replacement for any high tension wires that are broken, in compression (squeezed together or pinched) or have cracks in the insulation.
2. Inspect the solder connection on the transformer end of the high tension wire. If the connection is loose use solder to make the repair. If the connection is still loose make a replacement for the high tension wire.
3. Inspect the connector on the spark plug end of the high tension wire. The connector must be clean, dry, fit tight and be free of corrosion. If needed, clean the connector with a freon solvent.
4. Check the high tension wires for continuity.
1. Inspect the electrodes of the spark plugs. If the electrodes are worn (eroded) they can be made flat again with a small file. Foreign material (fouling) that is present on the electrode can be removed with solvent and the spark plug used again.
2. Measure the gap of the electrode. Make an adjustment if needed. The correct setting is .3 mm (.013").
3. Tighten the spark plugs to the correct torque when they are installed in their adapters. Make reference to the Operation Guide or Service Manual.
A manual that has complete service information for spark plugs is available from:
Service Engineering - VV
Attn: Staff Engineer - Gas Engines
100 NE Adams Street
Peoria, IL 61619
U.S.A.