Why my 1993 BMW 318i won't start?

fuel pump fuse is fuse no35 30A
or fuse no 40 20A
fuel pump relay is incorperated in the fuse box which is located behind glovebox

Do you have power to the relay? Checked fuses? ASD relay? Rollover relay? Bad ignition switch?

Check the main power relay.

Relay, on top of fuel tank under parcel shelf, check its getting power, if not its fuse, if it is, bin it get a new one.

Is there a check engine light on? Did car crank with old battery or you just replaced to see if would start?

check fuel pressure

Is the battery fully charged and if so you may have a bad starter..Good Luck!!!

Possible causes: Fuel pump relay, Pump, Fuel Filter, Regulator, Crank Shaft Sensor, Camshaft Sensor, Loos Connection(try to wiggle the wiring harness and observe). or faulty Ignation Switch.

Observe if the engine will lack of power first before to shut off, if this is the scenario it could be a fuel pump relay or pump. I suggest you to monitor the fuel pressure first or try to swap fuel pump relay to other as long as same color or figure and observe it.

If the senario is sudden cut off, it coud be a faulty cranck shaft sensor. a faulty cranck shaft sensor is easy to determine using tachometer while cranking, if the sensor is faulty the tachometer will not move or rise even a little bit if it's good it will rise a bit while cranking the engine.

Check fuel pump when the problem occur, try to ignition ON/Off and listen to fuel pump motor noise from underneath (close to rear right side tire), the pump will operates for aprox 5 sec. everytime you turned ON the ignition switch. and if you can't hear noise then you have to focus to fuel system.

It should be in the fuse box

Fuel pump may be getting weak. If pressure is not high enough the injectors wont open.