BMW 318/325/M3/525/535/M5 1989-1993 Repair Information

Fuel Pump

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TESTING



Electrical

See Figure 1



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Fig. Fig. 1: The fuel pump is located in the fuel tank and is accessible once the rear seat cushion is removed-E36 3 Series

When the ignition switch is first turned to START , the control unit will complete the ground circuit for the pump relay coil and the relay closes to run the pump. When the control unit receives a signal from the crankshaft pulse sensor, it will continue to operate the pump relay with the ignition switch in the RUN position. If the engine is not running, the pump will not run. The pump relay terminals can be jumped to test the electrical system and to run the pump for fuel system pressure testing.

  1. If a fuel supply problem is suspected, remove the pump relay and check for 12 volts at terminal 30 of the relay socket. With the ignition switch ON , there should be 12 volts at terminal 86 from the main DME relay.
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  3. Jumper terminals 30 and 87 on the relay socket. There should be power to the pump through fuse 23 (and fuse 24 if applicable) even if the ignition is OFF .
  4.  
  5. Use jumper wires to supply 12 volts to terminal 86 and ground to terminal 85 on the relay itself. Do not reverse the polarity or the relay will be destroyed. The relay should close and there should be continuity between terminals 30 and 87.
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  7. If the pump runs when the terminals are jumped and the relay is good, but the pump stops when the ignition switch is in the RUN position, the control unit may not be receiving a signal from the crankshaft pulse sensor.
  8.  

FLOW AND PRESSURE TESTING




CAUTION
The following procedure will produce fuel vapors. Make sure there is proper ventilation and take the appropriate fire safety precautions otherwise personal injury may occur.

  1. Make sure the battery is in good condition and the fuel pump wiring and ground connections are good. It is important the pump receive a full 12 volts.
  2.  
  3. Disconnect the fuel supply hose. Install a 13 3 60 or an equivalent 100 psi pressure gauge with a tee fitting.
  4.  
  5. Disconnect the fuel return hose and securely install a long hose to the return fitting. Place the other end into a 4 quart or 4000 cc measuring container.
  6.  
  7. Remove the fuel pump relay and connect a jumper wire with a switch to relay socket terminals 30 and 87. The pump will run whenever the terminals are connected, so be sure to use a jumper with a switch.
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  9. Run the pump for 30 seconds and time the run carefully. Except with the M42 and M50 engines , the pump should flow 29.6 oz. (875 cc) in 30 seconds and the pressure should be about 43 psi (3.0 bar). On the M42 and M50 engines, the pump should flow 34.8 oz. (1030 cc) in 30 seconds and the pressure should be about 58 psi (4.0 bar). When the pump is stopped, the pressure should stay above 38 psi (2.6 BAR) for 20 minutes.
  10.  
  11. If the flow is low, the pump is faulty or the filter is clogged.
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  13. If the flow is correct but the pressure is low or does not hold, clamp the return hose and run the pump again briefly to read the pressure. If the pressure is now correct and holds, the pressure regulator at the front of the supply rail is faulty.
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  15. If the pressure is still low or does not hold, there is a leak in the system, possibly an injector or the fuel pump check valve. The pressure will be lower if the engine is running because the pressure regulator will be supplied with engine vacuum.
  16.  

REMOVAL & INSTALLATION



Follow all precautions when working with gasoline and the resulting gasoline vapors. Relieve the fuel pressure before performing any work on the fuel system.


CAUTION
This procedure will generate gasoline fumes. Absolutely no flame or sparks should be in the area of the work being done. Gasoline fumes are heavier than air and will travel on the floor towards possible sources of ignition. Work in a well ventilated area and wipe up any gasoline spills. Gasoline will irritate skin; avoid contact with gasoline. Failure to follow these precautions may result in personal injury.

E30 3 Series
EXCEPT WITH S14 ENGINE
  1. If the tank is full, remove some fuel to lower the level.
  2.  
  3. Remove the rear seat cushion and peel back the insulating sheet to access the right side cover.
  4.  
  5. Remove the screws from the cover and lift the cover off. Pull of the electrical plug and disconnect the fuel lines. Catch any spilled fuel.
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  7. Remove the 4 screws from the sender portion of pickup assembly. Slowly remove the sender to allow the fuel to drain into the tank.
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  9. Rotate the pickup assembly counterclockwise and pull out slowly. Allow the fuel to drain back into the tank.
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To install:
  1. Replace the gasket and lower the pickup assembly into the fuel tank. Rotate the assembly clockwise to lock into place.
  2.  
  3. Replace the gasket and lower the fuel level sender into the pickup assembly. Replace the screws.
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  5. Connect the fuel lines and electrical connector. Replace the cover and the insulating sheet. Install the rear seat cushion.
  6.  

WITH S14 ENGINE

See Figure 2



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Fig. Fig. 2: The fuel supply system-E30 Series with S14 engine

The M3 is equipped with 2 fuel pumps. The main pump is located outside the fuel tank and is removed using the procedure below. The M3 also uses a pre-pump or transfer pump mounted in the fuel tank. The procedure to remove the tank mounted fuel pump is as listed in the previous procedure.

  1. Make sure the ignition switch is in the OFF position.
  2.  
  3. Use fuel line block-off clamps on the inlet and outlet lines of the fuel pump to prevent fuel from leaking out once the fuel pump has been removed.
  4.  
  5. Pull back the electrical connection covers and remove the wires. Loosen the hose connections and remove the hoses.
  6.  
  7. Remove the nuts holding the fuel pump and remove the assembly. Disconnect the hose from the pump and remove the pump from the bracket.
  8.  

To install:
  1. Install the pump in the bracket and connect the hose. Install the pump and bracket onto the car. Replace the rubber isolators if necessary.
  2.  
  3. Connect the hoses and the electrical connections. Remove the block off clamps.
  4.  

E36 3 Series

See Figure 3



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Fig. Fig. 3: The fuel pump and level sender assembly-E36 3 Series

  1. Drain the fuel from the fuel tank if the level is high. It is best to do this procedure with little fuel in the tank.
  2.  
  3. Remove the rear seat cushion and pull off the cover on the right side to expose the top of the fuel pickup assembly.
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  5. Disconnect the plugs on the top of the assembly. The black connector is for the fuel pump. The white connector is for the fuel level sender.
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  7. Mark and disconnect the fuel lines. Using tool 16 1 020 or equivalent, rotate the mounting ring and remove the assembly. Press the level arm in slightly to make clearance when removing.
  8.  

To install:
  1. The entire unit must be replaced. The individual parts are not serviceable.
  2.  
  3. Using a new seal and mounting ring, install the pump assembly. Move the unit from side to side to make sure the level sender is free and in the correct location. There is a rib on the flange that should align with a mark on the fuel tank.
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  5. Using tool 16 1 020 or equivalent, torque the mounting ring to 27-31 ft. lbs. (37-43 Nm).
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  7. Connect the fuel lines and the electrical connectors. Install the cover and rear seat.
  8.  

E34 5 Series

See Figures 4 and 5



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Fig. Fig. 4: The fuel pump and level sender assembly-E34 5 Series



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Fig. Fig. 5: Make sure the fuel pump retaining clips are fully engaged when installing-E34 5 Series

  1. Drain the fuel from the fuel tank if the level is high. It is best to do this procedure with little fuel in the tank.
  2.  
  3. Remove the trunk panels to expose the tank access cover on the right side, front corner. Remove the screws holding the cover.
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  5. Mark the fuel lines and disconnect them. Disconnect the electrical connection.
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  7. The models with M20, M30 and M50 engines are equipped with a large mounting ring that holds the fuel pump and level sender assembly. The mounting ring is removed using tool 16 1 020 or equivalent. The tool grips the edge of the mounting ring and allows the use of a breaker bar or socket wrench to remove the ring.
  8.  
  9. The M5 with the S38 engine has the fuel pump and level sender assembly retained with 8 screws or nuts around the perimeter. Remove the screws to remove the assembly.
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  11. Remove the assembly from the tank slowly to avoid spilling any fuel. The level sender with come out first. Compress the mounting hooks and remove the fuel pump.
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  13. Remove the hoses from the fuel pump and disconnect the wires. Unscrew the pressure damper and the check valve from the fuel pump and pull the pump out of the holder. Remove the fuel filter mounting screw and the fuel filter.
  14.  

To install:
  1. Install the fuel filter to the bottom of the fuel pump and install the pump into the holder. Install the pressure damper and the check valve. Connect the fuel lines and wires. The wires should be wire-tied to the fuel hose at the midway point.
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  3. Install the fuel pump into the tank and make sure the mounting hooks are secure on the fuel pump.
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  5. Replace the gasket and install the fuel level sender. Tighten the nuts or screws on the M5. On the mounting ring type units, using tool 16 1 020 or equivalent, torque the mounting ring to 27-31 ft. lbs. (37-43 Nm).
  6.  
  7. Connect the wires and the fuel lines. Replace the cover and the trunk trim.
  8.  

 
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