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Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 21619
Experience:  BEng hons Mech engineering, in auto industry 22 years
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1998 bmw 325i car starts and shut off after 4 seconds whats

Resolved Question:

1998 bmw 325i car starts and shut off after 4 seconds whats is the cause
Submitted: 2 years ago.
Category: BMW
Expert:  Matt replied 2 years ago.
Hello

this sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the injectors and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.
Customer: replied 2 years ago.

Its a new fuel pump and where the relay and fuse is located

Customer: replied 2 years ago.

I test tbe fuel pressure its 35psi

Expert:  Matt replied 2 years ago.
Hello Eldon

OK in that case this could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;
Airflow meter
Crank position sensor

O2 sensor
Throttle position sensor

unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.
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