Checking the fuel pump discharge pressure (BMW 5 Series E12)

"518"

Connect the test device as shown in the photo. If the vacuum created by the fuel pump is less than 0.5 kg/cm², replace the pump.

With the engine off, create a fuel pressure of 0.29-0.30 kg/cm² in the system by rotating the control device handle. With the carburetor needle valve closed, the fuel pressure in the system should not drop.

"520"

Connect the test device as shown in the photo. Start the engine, bring the crankshaft speed to 4000 rpm and measure the fuel pump discharge pressure, which should be 0.30 kg/cm².

Close valve 4 and check the tightness of the needle valve of the front carburetor. With the engine not running, use handle 7 of the device to set the fuel pressure in the system within 0.29-0.30 kg/cm². Close valve 6: the pressure should not drop.



Proceeding in the same way with valve 4 closed and valves 5 and 6 of the device open, set the fuel pressure in the system to 0.29-0.30 kg/cm². Close valve 5 of the device: if the needle valve of the rear carburetor is in good condition, the fuel pressure in the system does not drop.

"520i"

Install the pressure gauge and bracket 6070 as shown in the photo. Turn on the ignition and read the pressure gauge, which should be 2 kg/cm².

"525", "528"

Connect the test device as shown in the photo and open taps 1, 2, 3 of the device. Start the engine, bring the crankshaft speed to 4000 rpm and measure the fuel pump discharge pressure, which should be 0.21-0.25 kg/cm².

With the engine not running, check the tightness of the needle valve of the front carburetor. Close valve 1 of the device and use handle 4 to set the fuel pressure in the system to 0.29-0.30 kg/cm², which should not drop after closing the needle valve.



Check the tightness of the needle valve of the rear carburetor. Open tap 3 of the device, close tap 2, set the fuel pressure in the system to 0.29-0.30 kg/cm². This pressure should not decrease after closing the needle valve.

[You can find the original version on the portal: «BMWMAN»]