Testing and Adjusting
SMCS Code: 1250
Tests For The Air Inlet Heater
Right side of the engine.
(1) Air inlet heater
(2) Fuel supply line
(3) Fuel lift pump
(4) Electrical connection
(5) Fuel inlet
(6) Ball valve
(7) Valve holder
(8) Wire coil
(9) Ignition coil
The air inlet heater (1) is located In the air inlet manifold on the
right side of the engine.
The air inlet heater frequently appears to leak because the
ignition coil (9) is wet. The air inlet heater may be wet because
the diesel fuel does not burn completely. This condition is
normal. This condition does not indicate that the ball valve (6)
has fuel leakage. If a leak is suspected, perform the leakage
Check the heater operation by determining if the inlet manifold
is warm to the touch near the heater after approximately ten
seconds of operation. The inlet manifold should be warm.
Inspect the fuel tank and the fuel supply line (2) to the air inlet
heater for restrictions and leakage of fuel. Fuel flow through
the heater should be 3.5 to 5.9 cc/min (0.21 to 0.36 cu in/min).
Check the fuel shutoff valve for correct operation. A poor seal
on the fuel shutoff valve can cause air to enter the system
which will cause extra cranking of the engine before starting.
Be sure that all fuel connections are not leaking air.
Make sure that the battery condition and the battery charge are
satisfactory. Make sure that all electrical connections are tight.
The electrical system can have reduced voltage if the following
a discharged battery
a loose connection
Reduced voltage may cause slow cranking of the starter motor
and failure of the heater unit to be activated.
Do not operate the air inlet heater for a long
period of time. Operating the air inlet heater for a
long period of time can cause the components to
get too hot. Excessive heat can damage the
Leak Test For The Air Inlet Heater
Use the following procedure in order to test for a leak in the air
Disconnect the fuel supply line (2) and the electrical
connection on the air inlet heater. Be sure that the
electrical connector is insulated from contact with metal
engine components. Remove the air inlet heater from
the manifold. Place a suitable plug in the manifold in
order to prevent debris from entering the air inlet