Occasional non-starter
Moderator: martauto
Most times my 1984 323i starts immediately, but lately it’s a bit odd. It will either burst straight into life or just turn over but not catch. The battery is good and the starter motor kicks the engine around with plenty of torque, but the engine doesn’t start. Then if I leave it for a minute or two and try again it will give a click and fire right up. It also died at the lights yesterday . Again at first it didn’t want to go, then with a slight backfire it started. Any suggestions? Fuel pump?
Ah the joys of the L-Jetronic 
First port of call is a vacuum leak. Everything on that runs on vacuum. The idle control is a bellows that pushes the throttle open near the throttle cable. You should be able to see it move when you start and stop the car, without vacuum it will not work.
Look for obvious leaks then use the smoke or carb/brake cleaner method.
The slide valve may be sticking or losing vacuum, unfortunately they are NLA and hard to find in a working condition.
Better than I can explain is M539 restorations video
Good luck, it is why mine is going Motronic 1.3
First port of call is a vacuum leak. Everything on that runs on vacuum. The idle control is a bellows that pushes the throttle open near the throttle cable. You should be able to see it move when you start and stop the car, without vacuum it will not work.Look for obvious leaks then use the smoke or carb/brake cleaner method.
The slide valve may be sticking or losing vacuum, unfortunately they are NLA and hard to find in a working condition.
Better than I can explain is M539 restorations video
Good luck, it is why mine is going Motronic 1.3
Here you go
https://www.e30zone.net/e30wiki/index.p ... tronic_1.3
But, over the best part of 40 years, I have a bit of a love-hate relationship with the 2.3 in mine so when it comes back on the road it will be getting the 2.7 it deserves and it would be stupid not to run it on 1.3 even if I found a way of making Jetronic run a 2.7.