PREVOST LE MIRAGE XLII BUS SHELLS Maintenance Manual Download

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Section 03: FUEL SYSTEM

PA1564

MAINTENANCE

The primary and secondary fuel filters are of a
spin-on type and must be replaced every
12,500 miles (20 000 km) or once a year,
whichever comes first. If the primary fuel filter
is a fuel filter/water separator type, it is
equipped with a positive seal drain-valve to
prevent water infiltration in engine fuel system.
To drain, loosen positive seal drain-valve below
filter and tighten after water has been flushed
out.

A method of determining when filters are
clogged to the extent that they should be
changed is based on the fuel pressure at the
cylinder head fuel inlet fitting and the inlet
restriction at the fuel pump. In a clean system,
the maximum pump-inlet restriction should not
exceed 6 inches of mercury (20.3 kPa) and must
not exceed 12 inches of mercury (41 kPa) with a
dirty system.

At normal operating speeds and with the
standard fuel pressure regulator, the fuel
pressure at the cylinder head inlet is 50-75 psi
(345-577 kPa). Change the fuel filters whenever
the inlet restriction at the fuel pump reaches 12
inches of mercury (42 kPa) at normal operating
speeds. Also, change whenever the fuel
pressure at the cylinder head inlet fitting falls to
the minimum fuel pressure given above.

Change the filter cartridge(s) as follows:

NOTE

Use a suitable band wrench or filter wrench,
such as J22775, to remove the filters.

1. Stop engine and place a suitable container

under the filter.

2. Close the primary and secondary filter shut-

off valves (for valve location, See paragraph

"3. FUEL VALVES").

3. Using a band filter wrench, unscrew and

discard filters.

4. Fill new filter replacement cartridge(s) with

clean fuel oil, about two thirds (2/3). Apply a
thin coat of clean fuel oil on gasket.

5. Install new filters. Tighten until filter is snug

against the gasket, with no side movement.
Rotate an additional 1/2 turn by hand.

6. Open engine fuel supply line shut-off valves.

CAUTION

Mechanical tightening of the fuel filters is not
recommended and may result in seal and/or
cartridge damage. Tighten the fuel filters by
hand only.

5. Start the engine and check for leaks.

NOTE

There is a fuel system shut-off valve on the
discharge side of the secondary fuel filter.
This check valve is designed to prevent fuel
loss at time of filter replacement.

4.3 DAVCO FUEL PRO 382

The optional Fuel Pro 382 diesel fuel filter
system consists of a permanently mounted fuel
processor, a replaceable filter element, a filter
element cover and collar and a fluid filter base
assembly. This system is installed between the
fuel tank and the fuel pump and is designed to
be the only fuel filter in the fuel system. The filter
serves as a water separator as well as a fuel
filter (refer to figure 6).

The filter fibers used in the Davco Fuel Pro 382
element may cause the fuel level to read
artificially high when the filter is first installed.
Over the first few days, the filter fibers eventually
become fully saturated and the fuel level will
drop to normal levels. Do not be concerned
about an abnormally high fuel level when a new
Davco element is installed.

When new, the fuel level as seen through the
clear cover in the 382 filter is very low. It rises as
dirt collects on the filter from the bottom up.
Restriction remains consistently low because
fuel always flows through clean, new media.

MAINTENANCE

Replace Fuel Pro 382 filter element when the
fuel level in the see-thru filter cover reaches the
top of the filter element or after one year of
service, whichever comes first.

PREVOST LE MIRAGE XLII BUS SHELLS, Maintenance Manual

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