Troubleshooting an engine that wont start

[infidel1]

So, I haven't driven my 318I for a while. Started it right up to take to a car wash about a mile away. Finished and drove back home, parked and turned off the car. I just then remembered that I wanted to get the tires checked.
I re-started the car and turned around to head down the street in the other direction and then the engine began to run really rough. So much so that I didn't enough power to move the car in any direction. It was running so rough than eventually it died.... in the middle of the street. I tried to re-start the engine, but it just turned over without actually starting.
Fortunately I was able to push it back into my driveway.
So any idea about where to start looking?
Might this be fuel line/filter/pump issue?
Not sure where to start or what to check first.
Thank you for some tips.

[DeltaDConstruct]

As someone going through this right now with my new to me 325i here's how I'd approach it:
Pre Step 1: Perform a stomp test and see if you're getting any codes.

1: Check your fuses and relays [fuel pump and main]
2: Check for signal power to your fuel pump on prime
3: Check your engine grounds
4: Check resistance of your crank position sensor
5: Check fuel pressure at your pump and your fuel rail
6: Check DME for moisture or corrosion
7: Check for spark and injector pulse

Your car was running and it stopped, my guess is a fuel pump failure, but be sure to actually test before throwing money at the problem. Are you getting any other electrical weirdness or are you just not able to start the car?

[Eric93se]

I would suspect the DME got flooded when you went for a car wash. You could remove the negative on the battery, the remove then dme. Open it up and gain access to both sides. Check for white oxide tracks, if you find any then get a can of Deoxit 5% (guitar store, electronics store, Amazon, call first). Spray down both sides of the circuit board liberally and scrub with an old toothbrush, do this a second time. You would then have to let it 100% dry, compressed air can help, but you will need to wait 24hrs before putting it back in the car. If you do find oxide then post pics here for others to see (in focus pics lol).

- - - Updated - - -

You can spray down the connector part on the dme and the cable side connections, agitate with the brush.

[infidel1]

Thanks for the tips.
There are is no other electrical weirdness happening. The car just wont start.
It was running normally just a few minutes just before I parked and turned off the car.
It's when I restarted it to turn around when the engine suddenly started to run so rough, that it just died - and won't restart.
Because my car is a convertible with a few leak issues, I am very careful where the water goes. I'll double check, but I am pretty certain no water got up under the hood. And unfortunately, I don't have a code reader.

- - - Updated - - -

I appreciate the suggestion, I check out your suggestion, however I am pretty sure the problem isn't one of moisture.
I hand-washed my car except for the lower portion of the body.
It was running so normally just before I restarted the car. Then upon a restart, it just felt like the car was getting choked up, running rough and dying. This had never happened before.

[Eric93se]

On early e36's when large amounts of water hit the windshield the water goes through the cowl, the cowl floods due to poor drainage concept from bmw. Water is then able to flood into the DME compartment, early e36's the dme is not protected from moisture so it corrodes on the circuit board. Its possible that your fuel pump finally gave up the ghost, you can do a fuel pressure test.

[infidel1]

I understand.
I'll check the DME compartment and fuel pump.