Fuel Gauge - Sending Unit Check Procedure Update
88mitsubishi01SUBJECT:
PRECIS FUEL SENDING UNIT CHECK PROCEDURE - SERVICE MANUAL UPDATE
NO. TSB-88-08-003
DATE March, 1988
MODEL 1987-1988 Precis
TSB Revision: TSB-88-08-003
PURPOSE
This bulletin contains check procedures for the fuel sending unit of 1987 and 1988 Precis vehicles. These procedures should be used to diagnose and repair a malfunctioning fuel gauge or fuel sending unit. As reference to this bulletin, please write the TSB Revision number at the bottom of page 900-26 of the 1987 Precis Service Manual and page 90-21 of the 1988 Precis Service Manual.
FIGURE 1:
FUEL SENDING UNIT AND GAUGE LAYOUT
Figure 1 shows the location of fuel gauge, fuel sending unit and wiring harness for these components.
FIGURE 2:
FIGURE 3:
FUEL SENDING UNIT HARNESS CONNECTOR CHECK
A fuel gauge malfunction may be caused by a loose fuel sending unit harness connector or a loose pin in the connector which is located under the vehicle next to the fuel tank (RH side of tank). Make sure the connector is securely connected (Figure 2). A click should be felt after the connector is engaged. If the connector pins are loose when connected (Figure 3), the sending unit should be replaced.
FIGURE 4:
FUEL GAUGE CHECK PROCEDURE
Fuel Gauge Indication Test -
This gauge indication test requires that two resistors (1/2 watt/5% tolerance) be obtained; one 10 ohm and one 100 ohm. These resistors can be obtained from Radio Shack or any local electronics supply store. The Radio Shack part numbers are listed below:
10 Ohm - P/N 271-001 100 Ohm - P/N 271-012
1. Disconnect the fuel sending unit harness connector under the vehicle next to the fuel tank (RH side of tank) (Figure 4).
2. Using jumper wires, connect one end of the 10 ohm resistor to the positive pin (yellow/white wire) of the connector (gauge side) and the other end of the resistor to the ground pin (black wire) of the connector (Figure 4). Turn the ignition key to "ON". The fuel gauge should indicate just below full.
3. Exchange the 10 ohm resistor with the 100 ohm resistor and check the fuel gauge indication. The fuel gauge should indicate empty.
NOTE: If the resistors get mixed up, use an ohmmeter or the color codes listed below to identify the resistor.
Resistor Color Codes:
10 ohm - gold/black/black/red 100 ohm - gold/red/black/red
FIGURE 5:
Fuel Gauge Continuity Check -
If the fuel gauge indication tests OK as above, the following gauge continuity test is not required.
1. Remove the instrument cluster housing assembly (4 screws) and disconnect the harness connectors (Figure 5).
FIGURE 6:
FIGURE 7:
2. Remove the instrument cluster assembly (Figure 6) and disconnect the speedometer cable and harness connectors (Figure 7).
FIGURE 8:
3. Using an ohmmeter, measure the resistance between the fuel gauge terminals (screws) at the back of the instrument cluster as shown in Figure 8. The standard resistance value is 55 ohms.
4. If the resistance value is extremely low, there may be a short in the coil. If the resistance is very high, there may be a broken wire or another problem in the coil. Replace the fuel gauge as necessary.
FIGURE 9:
FUEL SENDING UNIT CHECK
1. Disconnect the fuel sending unit connector under the vehicle next to the fuel tank. Pry off the plate in the spare tire well and remove the sending unit from the fuel tank.
2. Using an ohmmeter, measure the resistance of the sending unit (Figure 9).
STANDARD
FLOAT POSITION RESISTANCE VALUE
E 110 +/- 7 ohms
F 3 +/- 2 ohms
FIGURE 10:
LOW FUEL WARNING SENSOR CHECK
1. Disconnect and remove the fuel sending unit from the fuel tank as described in step 1 above.
2. Connect a test lamp to the connector and immerse the sensor in a bucket of water (Figure 10).
3. The test lamp should not light when the sensor is immersed and should light when the sensor is removed from the water. If the lamp does not operate as descibed, replace the sending unit assembly.
4. Before installing the sending unit in the fuel tank, wipe the unit dry.