BMW of the 5th E28/E34 series - Repair manual and operation

6.6. System of catching of vapors of gasoline (EVAP)

General description

The scheme of the EVAP system on the M10 engine (the others - similarly)

This system is usually installed on the cars equipped with the catalytic converter.

When the engine is killed, fuel in the fuel tank evaporates, created pressure of vapors. The system of catching of vapors of gasoline accumulates these couples in capacity with an adsorber. On the run the valve of removal of vapors is a little slightly opened and fuel vapors gradually come to the inlet pipeline and burn down. When start of the cold engine is made or the engine idles, the valve of removal of vapors does not allow couples to come to the inlet pipeline and to enrich fuel mix excessively.

Valves of removal of vapors of two types are used: with electric management and vacuum management. To define what valve is installed on your car, track a hose from capacity with an adsorber, you will not find the valve yet. Some valves are installed on the inlet pipeline, others - near capacity with an adsorber. Look whether there is on the valve an electric socket or the vacuum line approaches it.

The faulty EVAP system influences road performance of the engine only when it is heated-up. The EVAP system usually is not the reason of difficult cold start or other problems on the cold engine.

Check

Valve of removal of vacuum-operated vapors

PERFORMANCE ORDER

Disconnect the vacuum line from the valve and blow in the bigger union of the valve. The valve has to be closed and air has to pass. On some models the thermal vacuum valve which interferes with removal of vapors is installed until temperature of a cooler reaches, about, 46 °C. Check this valve to be convinced of its operation under the influence of discharge at the correct temperature. The valve is usually located in the inlet pipeline near the temperature switch and the sensor of temperature of a cooler. Disconnect a thin vacuum hose from the valve of removal of vapors and the manual vacuum pump on an entrance of the valve create discharge. The valve has to open and begin to pass air. If the test yields negative result, replace the valve.

The valve of removal of vapors with electric management

PERFORMANCE ORDER

Disconnect from the valve all lines (except the electric socket) and move it to the place, convenient for testing. Check that the valve at inclusion of ignition publishes click. If the valve does not publish click, disconnect the socket from the valve and a control lamp or the voltmeter check power supply. If tension of the battery is present, but the valve does not work, replace it. If tension is absent, check the block of control Motronic and a wire.

Capacity with an adsorber

PERFORMANCE ORDER

Note an arrangement of all hoses, then disconnect them from capacity. Put forward capacity from a fixing collar. On some models it is necessary to weaken a collar. Visually check existence of leaks and damages for capacities. At detection of leaks and damages replace capacity.