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Volvo Bus Service and Maintenance Manual

 Fuel feed pressure and fuel filters
8 Measure the fuel feed pressure at the fuel filter outlet. The fuel feed pressure will normally determine when the filters must be replaced.
 Fuel tank
9 Check the fuel tank for cracks and its mounting. Drain condensation water. Clean the tank strainer.
10 Drain condensation water. Clean the tank strainer.

Fuel feed pressure

Before measuring the fuel feed pressure, increase engine speed and then lower it to low idle when reading off. Read-off the pressure within 1 minute.

The fuel feed pressure must be min. 100 kPa (1.0 kgf/cm2).

A low feed pressure will have a negative effect on the engine's peak power. In the event of complaints about engine output, the feed pressure should be checked during engine loading (same procedure as when checking the charging pressure). Low fuel pressure can be caused by contaminated fuel filters, a faulty relief valve or a defective fuel feed pump.

Engine fuel feed pressure test

Fuel filters

The presence of solid contaminants in the fuel will determine how often the filters must be replaced. If a check reveals condensation water in the fuel tank, the filters should be replaced when draining the fuel tank.

The normal interval for filter replacement is once a year or 100,000 km, but the distance can even be greater the better the fuel is filtered when topping-up fuel.

The filters should not be replaced too often since filterability improves after they have been in use for some time.

Replacing filters

Screw off and discard the old filters. Use tool 6670 if the filters cannot be removed by hand. Always replace both filters at the same time.

Removal of fuel filters

Fuel tank

The simplest way to avoid condensation is to ensure regularly that the fuel tank is full. A surface no longer covered by fuel leaves room for water deposits.

Before condensation water and impurities are drained, the bus should have been stationary for several hours to enable the impurities to collect in the bottom of the tank. Draining can be done without having to empty the tank.