Engine bogs & stalls

[afterglow]

I'm still working the kinks out on my newish 87 320i but today after driving around for around 1.5 hours (stop and go) the engine suddenly started bogging and eventually stalled and wouldn't start again. Engine cranks but it just wouldn't catch. Waited around five minutes and it started again just fine. Drove fine for the next 20 minutes or so then the same thing started happening again.

Fuel filter, ignition coil, spark plugs are new. Could it be the fuel pump?? Any ideas?

[dnguyen1963]

Do a smoke test with warm engine. I doubt that it is your fuel pump since the engine is running fine. How old is the O2 sensor? If it is over 100K then it is time to change.

[Eddie Haskell]

I would perform a fuel pressure check per Bentley. If you don't have a Bentley. You will need one. If no Bentley, just post and will describe.

[Andy.B]

It could be any issue with a the fuel injection system, as alluded to above.
Another issue that can cause similar behavior is sediments in the fuel tank clogging up the fuel pump intake 'sock' filter.

The strainer type filter in the tank sucks up fuel while the car is running, and keeps catching more and more sediments floating in the fuel until eventually it's all clogged up, starves the engine for fuel, and the car stalls.
Once the suction stops, the sediments start to separate from the strainer and float off into the fuel, and settle at the bottom of the tank.
You start and drive the car, and all is well again, until the fuel sloshes around, kicking up all the sediments, which eventually clog up the strainer again, causing the car to stall again.

The best way to diagnose the issue is the Bentley manual fuel system tests, but remember, a fuel pressure test would read fine, up until the point when the strainer gets clogged, and car gets starved for fuel and stalls. Then the fuel pressure will drop, but only briefly, until the sediments float away from the strainer. It's one of those tricky issues you have the 'catch in the act' so to speak.