jcb JS300 Service Manual page 545

Wires and Connectors
K Fig 60. Circuit ( T C-121)
Automatic Refill Mode
When the refuelling pump switch (C020) is pressed for less
than two seconds, there is an output from pin 2 to the wake
up diode (C127). A 'wake up' signal is sent via the diode to
an input on the MECU at connector J1 pin 22 (C015). The
DECU turns ON.
A signal is also sent to an input on the MECU at connector
J2 pin 19 (C016).
The MECU monitors the fuel quantity. If the fuel quantity is
at or below the pre-set 'auto refuel percentage' the
refuelling pump relay R5 energises via an output from the
MECU at connector J1 pin 27. The refuelling pump (C019)
operates.
When the fuel reaches the 'auto refuel percentage', the
MECU will de-energise the refuelling pump relay and
refuelling pump will stop.
If during automatic refuelling the fuel quantity does not
increase by at least 5% within 30 seconds (because the
source of fuel has run out or there is a blocked filter for
example) the MECU will de-energise the refuelling pump
relay and the refuelling pump will stop.
Note: The MECU will not energise the refuelling pump
relay if the engine is cranking or running. If the engine is
started during automatic refuelling the MECU will de-
energise the refuelling pump relay and refuelling will stop.
Note: If there are active fault codes related to the fuel level
sensor the MECU will de-energise the refuelling pump
relay and the refuelling pump will stop.
A second short press of the fuel pump momentary switch
will turn off the automatic refuelling mode and refuelling will
stop.
Manual Mode
When the refuelling pump switch (C020) is pressed and
held for more than two seconds the MECU sets the
refuelling pump operation to manual mode.
When the refuelling pump switch is pressed and held there
is an output from pin 2 to the wake up diode. A 'wake up'
C-120
signal is sent via the diode to an input on the MECU at
connector J1 pin 22. The DECU turns ON.
A signal is also sent to an input on the MECU at connector
J2 pin 19.
As long as the refuelling pump switch is held down the
refuelling pump relay energises via an output from the
MECU at connector J1 pin 27. The output remains on until
the refuelling switch is released. The MECU will de-
energise the refuelling pump relay and manual refuelling
will stop.
Note: If manual mode is entered from automatic mode,
then automatic mode is NOT resumed when the refuelling
pump switch is released.
C019
Fig 58. Harness connectors C019, C020
Fig 59. Wake up diode harness connector C127
9813/5100-1
Section C - Electrics
Engine and Power Control
Refuelling Pump
C020
C129290
C129300
C-120