Snap-On Diagnostics DGA 1000, Manual, Page: 65 / 116

Vehicle Testing
3-17
Disabling the Fuel System
Refer to the vehicle manufacturer’s procedure for disabling the fuel
system. Some common methods of disabling the fuel system
follow.
Disabling the Ignition System
Refer to the vehicle manufacturer’s procedure for disabling the
ignition system. Some common methods of disabling the ignition
system follow.
Always verify that there is no spark before injecting
propane into the intake.
Inertia Switch
– Most Ford vehicles are equipped with an inertia switch. Lifting the plunger
on the top of the switch deactivates the fuel pump. After "tripping" the
switch, crank the engine to burn any residual fuel in the fuel rail.
Fuel Pump Relay
– May be centrally located in the power distribution or maxi-fuse panels,
remove this relay to disable the fuel pump.
Fuel Injector Fuse(s)
– Usually located in the fuse panel, removing this fuse disables the fuel
injectors.
ECM/PCM Power Fuse(s)
– Usually located in the fuse panel, removing this fuse can disable the fuel
injectors. Sometimes it disables the fuel and ignition systems. Be sure to
check for spark.
IMPORTANT: Read trouble codes before removing fuses. Learned
memory may be erased when these fuses are removed.
External Coils and Coil Wire
– Disconnect primary wiring connector from ignition coil.
– Remove coil secondary wire from distributor cap and with a jumper wire
connect it to a known good ground.
Internal Coils
– Disconnect primary wiring connector from the distributor or from igniter
module.
Distrubutorless Ignition
– ECM/PCM Power Fuse(s) - Usually located in the fuse panel, these fuses
can be removed and the ignition may be disabled.
IMPORTANT: Read trouble codes before removing fuses. Learned
memory may be erased when these fuses are removed.
– Remove connector at ignition module, igniters or coilpack(s).
Ignition Control Relay
– Usually located in the power distribution or maxi-fuse panel, this relay
can be removed to disable the ignition system.
Ignition Control Fuse
– Usually located in the power distribution or maxi-fuse panel, this fuse can
be removed to disable the ignition system.