XJ-S V12-5.3L (1982)
Intake Air Temperature Sensor: All Technical Service Bulletins
Engine - Poor Hot Start, Poor Driveability
May, 1984
ITEM:
J84/23
SUBJECT:
HOT START PROBLEMS
MODEL:
XJ-S
Instances of poor hot start and poor running after start in high ambients or heat soak conditions have been reported. This may occur after the engine has
been run at full operating temperature and is left to stand stationary for 25-45 minutes.
The cause of this problem is fuel vaporization which is related to seasonal changes in fuel volatility made by the gasoline companies. Vaporized fuel in
the fuel rail will cause the mixture to go lean and can cause difficulty in starting. To overcome this condition, a temperature sensitive switch mounted on
the engine fuel rail and connected in circuit with the air temperature sensor circuit has been introduced at VIN-113546.
The fuel rail thermal switch contacts open at 70~C and disconnect the air temperature sensor causing a temporary enrichment of the fuel mixture. After
the engine starts, fuel pump operation will quickly purge fuel vapor in the system, the thermal switch will close as fuel rail temperature drops and normal
full mixture strength will be restored.
On the following VIN ranges, Recall A235 - Fuel Rail Replacement must be performed prior to fitment of thermal sensor switch:
Year/Model
VIN Range
1980 XJ-S
JNEV4AC
104236-105337
1982 XJ-S HE
SAJNV584*CC
105338-107987
1983 XJ-S HE
SAJNV584*CD
107988-111980
THERMAL SWITCH FITMENT INSTRUCTIONS
1.
Disconnect Battery.
2.
Screw the thermal sensor switch into the threaded receptacle in the fuel rail.
3.
Carefully slit the air temperature sensor harness covering approximately 152 mm (6.0 in.) from the air temperature sensor harness multiplug, so
that the two inner Yellow/Pink (YK), Red/Blue (RU) cables are exposed.
4.
Cut one of the cables and crimp or solder suitable bullet connectors to both ends.
