Fuel System - Engine Stumbles/Assumes Emergency Mode

SI B16 01 02
Fuel Systems

June 2002
Service Engineering

This Service Information bulletin supersedes S.I. B16 01 02 dated March 2002.

[NEW] designates changes to this revision

SUBJECT
Insufficient Fuel Transfer Inside Fuel Tank; Diagnostic Hints

MODEL
E65, E66

SITUATION
Engine stumbles and assumes emergency program. The fuel gauge indicates approximately 1/4 tank remaining. Fuel range indicates approximately 50 miles.

CAUSE
Insufficient fuel transfer from left to right half of the fuel tank caused by:

1. Siphon jet pump connection faulty at left fuel level sensor or fuel baffle.

2. Electric fuel pump not locked into position correctly.

3. Delivery capacity of electric fuel pump too low.

PROCEDURE

1. Check electric fuel pump speed in the right B-pillar airbag satellite module (SBSR).

^ Connect vehicle to DISplus or GT1.

^ From vehicle identification page, select SBSR (right B-pillar satellite) and perform individual short test.

^ Select "Control Unit Functions".

^ Under "Diagnosis Requests" select "Fuel Pump".

^ Highlight "Actual Engine Speed" and "Specified Speed".

^ Press "Display". Pump speed is displayed as "Actual Engine Speed". At idle, the requested and actual pump speed should be at least 3000 rpm (+/-100 rpm).

^ [NEW] If the requested speed is approximately 2500 rpm or lower, it will be necessary to re-program the vehicle. Refer to SI B 09 05 01 for CIP programming procedures.

2. If the speed of electric fuel pump is correct (appr. 3000 rpm), check the fuel transfer between left and right half of the fuel tank. With engine running at idle speed, this can be observed by monitoring the two fuel level sensors using instrument cluster test functions. For this test, fuel level should be less than 3/4 full.

^ To activate the instrument cluster display, press and hold reset button 10 seconds to enter test function menu.

^ Using reset button select test 19.

^ Press and hold button for 3 seconds to activate "Lock" display.

^ Using reset button, enter the sum of the last 5 digits of the VIN. Press and hold button for 3 seconds to unlock test functions. In the speedometer field, select test "06 Tank", by pressing and holding button for 3 seconds. Fuel levels of left and right sides of tank are displayed in the tachometer field.

^ If fuel level indicated by left sensor is greater than that of the right side, the fuel transfer should take place. At idle speed fuel should be transferred at a minimum rate of ONE LITER PER MINUTE. If both levels are equal and total volume is between 1/2 and 3/4 tank, it may be necessary to observe transfer after driving car through right hand turn (fuel forced to the left side). For fuel levels below 1/2 tank, at least 90% of total volume should be in the right tank side if transfer is working. Maximum level of right tank side is approximately 42 liters.

3. If no fuel transfer is observed, check operating fuel pressure (nominal value 3.5 bar) Refer to Repair Instructions 13 31 029 (M62/N62 procedure similar).

^ If fuel pressure is not OK, troubleshoot electric fuel pump (look for faulty pump, improper positioning in fuel baffle assy., etc.) and pressure regulator. Refer to Repair Instructions 13 31 000.

4. If fuel pressure is OK, check fuel return pressure between fuel filter and fuel tank (nominal value 0.8 1.2 bar).

^ If return pressure is OK, check siphon jet assembly in fuel tank (make sure that both sides are properly connected), and check siphon jet pump intake screen for debris. Replace if necessary.

^ If return pressure is too low, check return volume out of filter (nominal volume 1.0 liter per minute). If return volume is OK, check for secure attachment of the siphon jet assembly to the left fuel level sensor flange as well as the condition of the 0-ring seal on the flange. Check for proper attachment to fuel baffle assembly in right tank half. Check baffle for damage. If return volume is insufficient, replace electric fuel pump.

^ If return pressure is too high, check flow of return line between fuel filter and tank. Replace clogged line as necessary. If OK, check left fuel level sensor flange and in-tank siphon jet assembly for flow. Replace as necessary.

WARRANTY INFORMATION
For information only.