I am in need of a bit of advice for my 1990 740 GL non turbo 5 speed. The other day when i went to go and start the car, it turned over, started, and died immediately. After it initially died, i have not been able to get it to start again. It cranks but will not start. I have checked the fuel pump relays, and radio suppression relays and they are okay. I ended up replacing the fuel pump relay because i thought i could not hear it priming inside the tank but i was mistaken and i can hear it. I am leaning towards replacing the inline fuel pump, but i was wondering if anyone had any advice for other causes of this. Is there a way i can easily test to see if the no start is caused by the alternator? Also this was an all of a sudden thing, i have not had intermittent troubles with the car whatsoever. Thank You!

 

You can check your Radio Suppression Relay. It provides power to the fuel injection system. Search the forum here for where it is located (sorry, I'm only familiar with 240s which doesn't have the RSR)

 

verify you're getting spark when you crank it.

Use a fuel pressure tester before even thinking of replacing the fuel pumps... if you have pressure, they are good. note you'll need to crank to get fuel pressure...

use a 'noid light' to see if the injectors are getting pulsed when you crank it.

your alternator charges your battery when the engine is running. the car will run without an alternator, until the battery runs down, so its not going to be the cause of a no-start.

 

Like Pierce mentioned the no start won't be related to the alternator. You could literally pull the alternator off the car and it should still start and run (until the battery dies).

Have you checked all the fuses ??

Have you checked if you have spark ??

Have you tried to give the engine a small shot of starting fluid to see if it pops (if you have spark) ??