Issued June 2020
Compressed Natural Gas (CNG) Option
Copyright 2020, Heil Environmental
Printed in U.S.A.
234
CNG FUEL SYSTEM TROUBLESHOOTING (CONTINUED)
The following table lists possible problems, along with causes, corrections, and results.
CORRECTIVE/DIAGNOSTIC
ACTIONS
Heil Standard CNG and
Solenoid System
Options:
In-cab fuel gauge does not
indicate the fuel level
correctly.
The fuel module pressure
transducer, the fuel gauge
or the interconnecting
wiring may be defective.
Confirm that the 12-pin
electrical connector at the rear
of the fuel module is connected
and place the vehicle's ignition
switch in the "Run" position.
Use a voltmeter to read:
Voltage between connector
positions 2 (RED) and 3
(BLK). the voltage should be
12 vdc.
Voltage between connector
positions 3 (BLK) and 4
(WHT). the voltage should
be between 0.5 to 5.0 vdc.
*If the voltage across 2
and 3 is 0 or significantly
below battery voltage,
there is a problem with the
vehicle's wiring not
supplying power to the fuel
module's pressure
transducer.
*If the voltage across 3
and 4 is either 0 or 5.5
vdc, the fuel module's
pressure transducer is
most likely defective. Call
866-310-4345 for technical
assistance.
*If the voltage across 3
and 4 is between 0.5 to 5.0
vdc then the fuel module's
pressure transducer is
operating correctly. The
problem is likely in the
vehicle's wiring or the in-
cab fuel gauge.
*If the problem cannot be
resolved, call 866-310-
4345 for technical
assistance.
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