|
|
Page 11
Lotus Service Notes
Section LK The third, 'purge' port, controlled by a solenoid valve mounted on the inlet manifold, connects the underside of the charcoal bed with a port on the engine intake plenum. The pulse width modulated vapour management valve is opened during certain engine running conditions in order to allow intake depression to draw fresh air through the vent pipe and charcoal bed, cleansing the charcoal of fuel before consuming the resultant vapour in the normal combustion process. In this way, the charcoal is prepared for further vapour absorption. Control System The vapour manageement valve is controlled by the engine management ECU, which keeps the valve closed (unenergised) when the engine is cold or idling in order to maintain idle quality. At normal running tem- peratures and engine speeds above idle, the ECU monitors other running conditions and the status of various management systems, and when appropriate conditions pertain, the ECU will apply a duty cycle to the valve in order to regulate the amount of purging allowed dependent on the amount of vapour in the canister. LK.7 - FUEL TANK PRESSURE TEST In order to verify the sealing integrity of the fuel tank and filler system, the following test should be per- formed: 1. Use the Lotus Scan tool to close the canister vent valve or apply 12 volts and ground to the two terminals of the vent valve electrical connector. 2. Locate the test port in the purge line between the canister and vapour management valve (VMV), which is itself mounted on an inlet manifold plenum bracket, and connect an appropriate tester or pressure pump and water manometer as shown in the diagram. 3. Pressurise the tank to 20"H 2 O (5.0 kPa). 4. Allow to stabilise for 30 to 60 seconds then take a reference point and start measuring the pressure decay over a period of 60 seconds. Typical pressure reduction over this period should not exceed the region of 1" H 2 O (0.25 kPa). Pressure loss of between 2" H 2 O (0.5 kPa) and 3" H 2 O (0.75 kPa) will cause the MIL to be illuminated and a trouble code (P0456 - minor pressure loss) to be set. Minor leaks equivalent to a 0.5 mm (0.020 inch) hole, may be caused by: - Inadequate sealing of the VMV. To verify, clamp off the flexible hose between the VMV and inlet manifold and repeat the test. A significant improvement indicates a suspect valve. Clean or renew. Pressure pump Test with gauge port Charcoal canister To intake plenum
L65 Vapour Management Valve sn_lk_croft.indd 11 03/03/2006 11:22:31 |