The pressure in the fuel injected system is enough to cause the fuel to spray from the line that is being opened. If the fuel is allowed to spray from the line it could be ignited by a spark. Pressurized fuel spray could also squirt into your eyes and cause severe injury.
RELIEVING SYSTEM PRESSURE
To relieve the pressure in fuel injected systems, first find the fuel pump relay plug, located on the cowl in most vehicles. Unplug the relay, leaving it in a safe position where the connections cannot ground. If necessary, tape the plug in place or tape over the connector prongs with electrical tape. Then, start the engine and operate it until it stalls. Crank the engine for 10 seconds after it stalls to remove any residual pressure.
REMOVAL & INSTALLATION
See Figure 1
1600, 2000, 2002, 2002Tii, 2500,2800, BAVARIA, 3000CS, 3.0CS AND 3.0S MODELS
On all carbureted models, the fine mesh filter screen in the fuel pump is removed at 8,000 mile (13,000 km) intervals for cleaning. On 1600 models, this is accomplished by removing the cover plate bolt. On all other models, this is accomplished by removing the filter sieve retaining bolt. Discard the old sealing ring and wash out the filter sieve in clean gasoline or kerosene. On 1600 models, clean the cover plate also. On all others, replace the filter sieve using a new sealing ring, and tighten the retaining bolt. At this time, check that the bolts on the fuel pump are evenly tightened using a screwdriver.
On many fuel injected models, a total of 4 fuel filters must be cleaned or replaced. Three are serviced at 40,000 mile (64,000 km) intervals. The fourth, or main filter should be serviced at least every 8,000 (13,000 km) miles.
Each filter consists of a fine mesh which filters the fuel in the fuel tank pick-up, electric fuel pump, engine compartment and the mechanical fuel injection pump.MESH STRAINER IN FUEL TANK
- On the 320i models, remove the rear seat to gain access to the unit. On 3, 5 and 7Series models, remove the left luggage compartment floor panel. On the 3.0Si and 6 Series models, remove the right side luggage compartment floor panel. On all other models, remove the right hand floor panel that covers the fuel tank in the trunk.
- Unfasten the electrical connector.
- On 320i and 3.0Si models, remove the bolts or nuts, then detach the hoses. Pull the pump/sensor unit out of the tank,. On the remaining models, unplug the hoses, and turn the unit counter clockwise using screwdrivers or other suitable tools as levers.
- Cleaned the strainer in fresh gasoline or kerosene.
- Install the unit in reverse order, using a new gasket and making sure to plug in hoses securely and check for leaks before replacing the luggage compartment cover or sear.
To clean the fine mesh filter in the electric fuel pump, the following procedure is used:
- Locate the fuel pump underneath the car near the differential housing.
- Loosen the hose clamp on the fuel feed pipe. Disconnect and plug the end of the feed pipe with a suitable object.
- Pull out the thimble-sized, bag-type fine mesh filter from the pump and clean it in clean gasoline or kerosene.
- Reverse the procedure to install.
See Figures 2, 3 and 4
To replace the in-line main fuel filter, the following procedure is used:
- Loosen the hose clamps and the filter retaining clamp. Mark the fuel line for reassembly.
In some models, battery removal may facilitate better access to the fuel filter.
- Disconnect and plug both fuel lines, remove and discard the old filter.
- Install a new filter, taking care to note the prescribed direction of flow shown on the filter label.
To clean the fine mesh filter in the fuel injection pump, the following procedure is used:
- Remove the 17mm hollow screw in the fuel inlet pipe.
- Clean the thimble-sized fine mesh filter located in the hollow screw using clean gasoline or kerosene.
- Reverse the above procedure to install.
These filters are located as follows:
- Loosen the hose clamps.
- Remove the filter unit.
- Replace it with a new filter, making sure the arrow indicating direction of flow is facing the same direction as with the old unit (away from the tank).
- Loosen the intake hose clamp on the fuel pump. This is located above the right rear halfshaft.
- Remove the fine mesh basket type filter, located inside the hose connection.
- Clean the filter in fresh gasoline or kerosene.
See Figure 5
- Loosen the bleeder screw located on top of the filter mounting using a regular screwdriver.
- Place a container under the filter and loosen the draincock to drain a small amount of fuel. This will prevent fuel from spilling when the filter is removed.
- Disconnect the plug on the water level sensor. Unscrew the filter with a standard oil filter strap type wrench.
- Remove the water level sensor from the old filter and install it over to the new filter.
- Thoroughly coat the seal on top of the new filter with clean diesel fuel. Start the filter onto the threads. Turn it until the gasket touches, and then turn it just one half turn more by hand.
- Disconnect the plug for the fuel transfer pump. Open the bleeder screw. Jump terminals 30 and 87 of the pump relay. When the fuel flow is bubble-free screw, tighten the screw. Remove the jumper and reconnect the plug.
- Start the engine and operate it to check for leaks. Tighten the filter just a bit further, if necessary.
DRAINING WATER FROM THE FUEL SYSTEM
Due to the chemical make up of diesel fuel, it is prone to hold water. The fuel filter in the diesel fuel system is designed to separate this water from the fuel before it reaches the injection system.
Periodically this water must be removed from the filter canister or the filter will become full of water, causing water to enter the injection system. The water can be drained as follows:
- Hold a half pint container under the bleeder screw and open the draincock.
- See Step 5 of the procedure above for fuel filter replacement, and activate the fuel transfer pump by jumping terminals 30 and 87.
- Press the drain adapter in, and allow it to drain until pure fuel runs out.
- Remove the jumper wire and tighten the draincock.