Checking Fuel Tank & Tank Venting System For Leaks With Tank Leakage Diagnosis Module (DM-TL) - 5-Series (E39) V8
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- Remove left rear wheel. Remove left rear wheel housing trim. Remove leak diagnosis pump air cleaner from retaining bracket of activated carbon filter from below. See Fig 1. Using hose clamp, seal with Special Tool (16 1 161).
- Remove tank filler cap and connect Special Tool (16 1 150) to tank filler neck. See Figure. Screw in rear towing eye and hook Special Tool (16 1 150) into it. Connect special tool to compressed air system of 116-145 psi (8-10 bar) with compressed air hose. Connect pressure sensor with measuring range of 0-51 psi (0-3.5 bar). See Figure.WARNING: Ensure pressure regulator on Special Tool (16 1 150) is set completely in "-" direction and non return cock between pressure regulator and pressure sensor is closed.
- Select MEASURING TECHNOLOGY function on Diagnosis and Information System (DIS). Set measuring range in accordance with pressure sensor to 0-51 psi (0-3.5 bar). Open non return cock on Special Tool (16 1 150) and increase pressure in tank system by.72 psi (.05 bar) with pressure regulator.WARNING: Do not increase pressure by more than 1.45 psi (.10 bar) as damage to fuel tank and tank ventilation system is possible.
- Close non return cock. Wait for about 20 seconds for system to settle, read off pressure value, then wait for 60 seconds. Read off final pressure value and compare with starting pressure value. If pressure drop is.116-1.7 psi (.008-.12 bar), measurement must be repeated to obtain a confirming result. If pressure drop in 60 seconds is greater than.145 psi (.010 bar), system is leaking.
- Leak test can be carried out with a leak detector. Possible causes may be fuel filler cap leaking, tank ventilation line leaking (fuel tank-activated carbon canister-tank ventilation valve), tank ventilation valve leaking (engine compartment), tank sensor on fuel tank leaking or activated carbon canister non return valve leaking (spare wheel recess).