Fuel Delivery and Air Induction: Description and Operation

GF07.61-P-3004MS ME Fuel Supply, Function
- up to model year 08

Component Identification:

The fuel supply system must make available to the fuel injectors (Y62) an adequate quantity of filtered fuel from the fuel tank and at an adequate pressure in all operating conditions.
The fuel injectors operated by the ME-SFI [ME] control unit, spray the finely atomized fuel into the inlet ports.

The fuel pump is a two-stage flow pump with a minimum delivery rate of 230 liters/hour. It draws fuel from the swirl pot in the fuel tank and delivers it to the fuel filter, where contaminants are removed. The fuel pressure sensor records the fuel pressure downstream of the fuel filter.

Engine 275.953
The signal from the fuel pressure sensor with the current fuel pressure is read in at the fuel pump control unit and reported via the drive CAN to the ME-SFI control unit.

Engine 275.982
The signal from the fuel pressure sensor with the current fuel pressure is read straight in at the ME-SFI control unit.

The fuel pressure is checked for plausibility in the ME-SFI [ME] control unit and sent back to the fuel pump control unit as a fuel pump target preset. Via PWM signals, the delivered volume (speed) of the pump is then regulated so that the delivered system pressure (constant up to around 3.8 bar for engine 275.953 or 3.6 to 5.0 bar for engine 275.982 with AMG) is achieved.

The fuel from the overflow valve supplies the suction jet pump in the left fuel tank chamber. The overflow valve opens via fuel pressure at approx. 3.0 bar. The fuel feed to the suction jet pump is a limited by a nozzle (approx. 0.5 mm) in the suction jet pump to approx. 50 l an hour.

Fuel vapors out of the fuel tank are temporarily stored in the activated charcoal canister and combusted via the purge control valve during suction operation in the engine.

A check valve in the purge line prevents the boost pressure building up toward the activated charcoal canister.

If the faults "Fuel pressure too low" and "Misfires" are stored, check the fuel pump delivery rate at the feed to the fuel distributor rail (not at the pressure gauge connection.).
If the fuel pump is fully actuated (menu item in STAR DIAGNOSIS), approx. 1 liter (AMG 1.25 liters) of fuel must flow through the pump in 15 seconds. The cause may also be a contaminated fuel filter. The fuel pressure and volume flow through the flow pump can be read out using STAR DIAGNOSIS.

Engine 275.982 AMG
AMG vehicles operate with a variable system pressure of 3.6 to 5.0 bar. The system pressure is regulated according to power output requirements and outside temperature so that a rapid response time of the engine in all load ranges is ensured.

A powerful fuel pump with 3 windings and an adapted fuel pump control unit are installed to do that. The fuel pump is actuated via 3 phase-offset PWM signals.