PUMP GP-UNIT INJECTOR HYD 2206214 - Caterpillar

new, schematic Special Instruction is available to make testing with the 5P6590 Wiring Harness Tester Group easier. Each test that can be made with the tester has a number and a name. The numbers and names make it easier for a serviceman to test the components of the electrical system in the correct sequence. This Special Instruction is not a replacement for any existing information written about electrical system testing.
Special Instruction Form SEHS7153 is made of a material that has more resistance to fire, heat and oil, and does not tear (break) as easily as normal paper Special Instructions. It is our recommendation that you keep this Special Instruction in the tester box.
Normally, the 5P6590 Wiring Harness Tester Group is used to check the electrical circuits on all tandem-powered Caterpillar Tractor-Scrapers and Caterpillar Off-Highway Trucks. But, the tester can also be used to test any electrical circuit of 24 Volts, test and shift (change speeds) transmissions on the hydraulic test stand.
General Information: When troubleshooting any electrical system, our recommendation is to start with the battery. A battery test will determine if the battery or batteries are charged correctly. Readings from a test of a 24 volt battery will show the conditions that follow:
A low reading is an indication that the battery needs to be charged. But for a very low reading, a more thorough test is needed. Test the voltage again and the specific gravity of the electrolyte in the separate cells. Use the 5P957 or 5P3514 Coolant and Battery Tester to check the specific gravity. Follow the recommendations below when voltage and specific gravity are used to check the condition of the battery or batteries:
Use the circuit voltage test to check for normal operation of an electrical system. The lamps of the tester will be activated when a complete circuit is made. The lamps are for a 24 Volt system and are not visible (activated but not seen) in the range of 10 Volts or less.
In this voltage range, a meter can be used for the Circuit Voltage Test to check for complete circuits. The meter can also be used to check the voltage decrease in a circuit. Normally, there is a 1.0 to 1.5 Volt decrease when a solenoid is activated. This is caused by a current flow through the solenoid back to the battery.
Use the Circuit Continuity Test-Ground Seeking to find a damaged (frayed) or broken harness. This is a common problem which causes a short circuit. If a continuity test lamp becomes visible as the serviceman turns the selector switch, this is an indication of a ground on the circuit respective to the selector switch position. This same test can also be used to check for open circuits. The opposite end of the harness is grounded. If there is an open circuit, the continuity test lamp will not become visible at the selector switch position.
Use the Circuit Continuity Test-Short Seeking to find internal continuities. Turn the selector switch of the tester. If any of