300Tdi Discovery
MFI
1
FAULT DIAGNOSIS
ENGINE TUNING
Circuit fault diagnosis may be carried out on all V8i
vehicles, using Testbook. Testbook will guide the
operator by visual prompts through a series of
diagnostic checks.
Before commencing any fault diagnosis, the following
preminary checks must be carried out.
Preliminary checks
CAUTION: Catalyst exhaust: If engine is
misfiring or fails to start within 12 seconds
the cause must be rectified. Failure to do
so will result in irreparable damage to the
catalysts. After rectification the engine must be
run at 1500 rev/min (no load) for 3 minutes to
purge any accumulation of fuel in the system.
1. Check that the inertia fuel shut off switch is not
tripped.
2. Check fuse in main fuse panel.
3. Check for ample fuel in tank.
4. Check air inlet system for possible leaks into the
intake manifold.
5. Check HT cables for correct firing order and
routing.
6. Check ignition timing.
Only when the above checks have been carried out,
should circuit diagnosis begin.
See Electrical
Trouble Shooting Manual.
INJECTOR TESTS
NOTE: Before removing any of the
injectors, remove and examine the spark
plugs, check for consistent colouration of
plugs. A leaking injector will result in the
appropriate spark plug being ’sooted up’.
The following test may only be carried out using
suitable injector test equipment.
Leak Test
Leak test with the injectors closed but pressurise to
2.54 Kgf/cm
2
. No injector should leak more than 2
drops of fuel per minute.
Fuel Delivery Test
Fuel delivery test with the injector open and
pressurised as above, fuel delivery from each injector
should be 160-175cc per minute using white spirit, or
180-195cc per minute using petrol at 20
°
C
±
2
°
C.
