Circuit Description
The fuel manager/filter assembly consists of the fuel heater, the water-in-fuel sensor, and a filter. The filter contains the coalescer, the device that combines small droplets of water into larger ones, and the filter/separator.
As the fuel enters the filter, the fuel passes through the fuel heater. The heater contains a thermostatic switch that opens or closes to turn the heater OFF or ON, depending on the temperature of the fuel.
The fuel then passes through the filter and the water coalescer, where the droplets of water in the fuel combine into larger drops that fall into the water reservoir in the filter. When fuel flows from the fuel manager/filter assembly to the injection pump, the fuel is clean and free of water.
The fuel heater is operated by a built-in thermostatic switch. The thermostatic switch completes the circuit for the fuel heater element when the thermostatic switch senses a temperature below 15.4°C (59.8°F).
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Does the Water In Fuel lamp operating properly? | -- | Go to Step 2 | Go to Water-in-Fuel Lamp Always On in Instrument Panel, Gages, and Console |
2 |
Does the test lamp illuminate? | -- | Go to Step 3 | Go to Step 5 |
3 | Probe the fuel heater ground circuit at the fuel filter/heater element housing with a test lamp connected to B+. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the test lamp illuminate? | -- | Go to Step 4 | Go to Step 10 |
4 |
Did either circuit test open? | -- | Go to Step 11 | Go to Step 7 |
5 | Is the fuel HT fuse open? | -- | Go to Step 6 | Go to Step 8 |
6 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 7 |
Does the thermostatic switch turn ON when the temperature is within the specified range? | -8.4 to +15.4°C (+16.9 to +59.8°F) | Go to Step 13 | Go to Step 12 | |
8 | Repair the open in the ignition 1 voltage circuit between the fuel filter/heater element housing and the Fuse. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
9 | Repair the short to ground on the ignition 1 voltage circuit . Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
10 | Repair the open in the ground circuit between the fuel filter/heater element housing and chassis ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
11 | Replace the fuel filter/heater element housing. Refer to Fuel Filter Assembly Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
12 | Replace the fuel heater. Refer to Fuel Filter Assembly Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the intake air heater relay. Refer to Intake Air Heater Relay Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 | Operate the vehicle under which the problem was noted. Does the system operate properly? | -- | System OK | Go to Step 1 |
