DAF 95XF. Manual - part 168
©
200438
3-3
System inspection with DAVIE XD
UPEC
DAVIE XD diagnostics manual
2
3.3 SPEED VARIATION CONTROL TEST
One of the controls of the engine management
system is the uniform operation of the engine via
the speed variation control (this speed variation is
recorded via the crankshaft sensor).
Too large a variation in speed is prevented by
correcting the quantity of injected fuel per
cylinder.
Due to a fault in the fuel system (bad injector, fuel
leakage etc.) the fuel correction applied to a
cylinder may have increased to such an extent
that it falls outside the permitted specification.
Note:
Bear in mind the fact that a mechanical defect in
a cylinder (compression loss) may affect the fuel
correction for another cylinder that falls outside
the permitted specification.
Here the relation is as follows:
In the "speed variation control" test the fuel
correction of each cylinder is determined during a
trip cycle (a trip cycle where a high engine load is
required for a long period), on the basis of the
total fuel consumption.
The "speed variation control test" in DAVIE is one
of the diagnostic tools that can be applied in case
of complaints about fuel consumption and
reduced engine power.
Other tests are the acceleration test and plotting
a boost pressure curve; in principle these have to
be carried out before the "speed variation control
test" is carried out.
in case of compression loss of cylinder:
1
5
3
6
2
4
a positive fuel correction on cylinder:
3
6
2
4
1
5