TM 5-2420-230-24-2
B3.9 and B5.9 Series Engines
AFC Assembly (005-001)
Section 5 - Fuel System - Group 05
Page 5-9
AFC Assembly (005-001)
General Information
Air-Fuel Control (AFC) Malfunctions
The RQVK governors are equipped with an air-fuel control
(AFC) device to help control emissions. The AFC regulates
the fuel-to-air mixture by sensing manifold pressure. A
malfunction of the AFC can cause low power or excessive
exhaust smoke under load. Leaks at the fittings or a re-
striction in the tube from the intake manifold to the AFC can
also cause low power.
Engine Fuel Heater, Electric (005-008)
Initial Check (005-008-001)
NOTE: The fuel heater is not controlled by the electronic
control module (ECM). A bimetallic strip on the filter head
acts as a thermostat. The fuel heater will turn on at ap-
proximately 1C [34F] and turn off at approximately 18C
[64F].
Remove the 2-pin connector from the fuel heater.
Using an ohmmeter, check the continuity of the fuel heater
by placing the ohmmeter test leads across the pins of the
fuel heater.
If the heater circuit is open, replace the fuel heater.
Check for proper voltage to the fuel heater.
Minimum Voltage
12 VDC
If voltage is not within specifications, refer to the OEM
service manual.
Remove (005-008-002)
Disconnect the connector from the fuel heater.
Disconnect the connector from the water-in-fuel (WIF)
sensor.
L-869