BMW Coupes and Sedans 1970-1988 Repair Guide

Fuel Pressure

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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.

3.0Si Models

Install a pressure gauge in the line between the fuel filter and the injector feed circuit. The pressure must be 31.2 psi (212 kPa). If not, adjust the pressure. If that will not correct low pressure, replace the pump.

The fuel pressure regulator is located in the circuit which feeds all the injectors between 2 of the injectors. An adjusting bolt and locknut protrude from the top. To adjust it, connect a pressure gauge and idle the engine as described in the pressure check above, loosen the locknut, turn the bolt in or out until the pressure is correct, and then retighten the locknut.

1982-86 325e, 528e, 533i, 633CSi and 1982 733i Models

Relieve fuel system pressure, as described in this section. Connect a pressure gauge in the line leading to the cold start valve from the injector feed circuit. With the engine idling, the pressure must be 33-38 psi (224-258 kPa), or the fuel pump (or filter) is defective.

1987-88 3 Series Models
  1. Relieve fuel system pressure, as described in this section. Tee a pressure gauge into the fuel feed line in front of the pressure regulator.
  2.  
  3. Disconnect the fuel pump relay. Connect a remote starter switch between terminals KL30 and KL87 of the relay. Close the switch and check the pressure. It should be 43 psi (292 kPa). If not, the filter is severely clogged or the fuel pump is defective.
  4.  

M3 Models
  1. Relieve fuel system pressure, as described above. Tee a pressure gauge into the fuel return line at the pressure regulator. Then, clamp off the return line so pressure builds up to the maximum level the pump can produce.
  2.  
  3. Remove the trim from the cowl on the right (passenger's side). Then, unplug the fuel pump relay. Connect a remote starter switch between terminals 30 and 87 (left side and top holding the male side of the connector). Energize the switch and check the pressure. It must be 43 psi (292 kPa). Check the filter for excessive clogging. If it is okay, the pump is defective.
  4.  

1983-88 533i, 535i, 633CSi, 635CSi,733i, 735i, M5 and M6 Models

  1. Relieve fuel system pressure, as in this section. Tee a pressure gauge into the fuel feed line in front of the pressure regulator (on M5 and M6 models, tee in between the cold start valve and the fuel rail). Plug the fuel return hose.
  2.  
  3. Pull off the pump relay. Jumper terminals 87 and 30. Measure the delivery pressure. It should be 43 psi (292 kPa) on these models except the 1987-88 735i. On these models, it should be 48 psi (326 kPa).
  4.  

 
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