E30 335i won't idle for more than like 30 secs, ???

[The München Monster]

Thought it was the battery so replace that and with a brand new battery it still died in like 15 to 45 seconds. The problem began as intermittent dying in traffic and now its undriveable. Plugs and leads are fine, fuel pump and lines appear ok. could it be alternator, fuel filter,or maybe still pump??? Any ideas (Yes i posted this but i cant find the old post). 1988 M30B35

[curtis_luu]

alternator is my guess.

If the car dies, take out the battery, charge it, and put it back in.
If it starts back up and then dies similarly, i'd assume its the alternator.
Check the belt for looseness as well. (may not need to buy a new alternator)

[ahlem]

Put a tee in your fuel line and check the fuel pressure for real. You can try pinching off the return line from your fuel pressure regulator to see if it's bleeding off fuel pressure.
If it has good fuel pressure you can move on to something else.