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dure over and over with little or no long-term improvement. Consider using a capacitive probe or our P-
300M Magnetic fuel probe if at all possible.
Symptom:
Symptom:
Symptom:
Symptom:
Symptom: Inaccurate, jumpy or zero reading.
1. Problem: The RFLM is mis-wired.
a) Action: Remove the signal wire to the Resistive Float. Check for a very high (or low,
depending on the float type) sensor count in the “Function Mapping" screen
found in the "Function Configuration" screen. Be sure you are displaying the
data for the correct tank.
The voltage on the open signal wire should measure bus voltage.
Short the signal wire to ground. Check the sensor counts go to a low (or high,
depending on the float type) reading.
2. Problem: The Resistive Float does not operate properly.
a) Action: With the signal wire removed, measure the resistance of the float. This should
not be done with a full or empty tank but somewhere in-between. Record the
resistance reading and the variations. Lift the wing and allow it to return to its
original position. Record the resistance reading and the variations. This test
can be done at different fuel levels. If the resistance value does not return to its
original value, you may have a defective Resistive Float.
Symptom:
Symptom:
Symptom:
Symptom:
Symptom: The sensor counts decrease as you add fuel.
1. Problem: The probe selected in the “Function Configuration" screen may be the wrong probe.
a) Action: Check the Probe selected in the “Function Configuration” screen. The “RFLM-
4 H=F” probe should be used on Resistive Floats where high resistance = full
tank readings and the “RFLM-4 L=F” probe should be used on Resistive Floats
where low resistance = full tank readings.
7.9 Capacitive Fuel Level Problem:
Fuel can be measured in a fuel tank using a Capacitive Fuel Probe. The Electronics International P-300
Capacitive Fuel Probe connects to an IMC (Interface Module) located near the probe, and to the EDC
through three wires. Power (+5 volts) is supplied on the Red wire, ground is supplied on the Black wire
and the fuel level signal (a 0 to +5 volt square wave) is supplied (by the P-300C) on the White wire.
As the fuel level in the tank increases, the capacitance of the probe increases. The IMC Module converts
the capacitance to a frequency. The higher the fuel level, the lower the frequency of the square wave on
the White wire.
The EDC monitors the signal and produces a digital value (called sensor counts) based on the signal fre-
quency. The sensor counts can be viewed in the “Function Mapping” screen. The sensor counts are then
converted to a fuel level based on the calibration data in the “Function Mapping” screen.
Symptom:
Symptom:
Symptom:
Symptom:
Symptom: Inaccurate, jumpy or zero reading.
1. Problem: The IMC is mis-wired.
a) Action: Measure the voltage on the three wires at the IMC Module (Red wire = +5 volts,
