Car starts, but stalls immediately

[michael1234]

Hi,

I'm new here. I'm from Edmonton, Canada, and got a 1984 733i in September 2018. The car ran great so far, but I had to deal with some rust on the the A pillar and floorpans recently. This weekend I mostly assembled the interior, but now the car does not start properly. It is possible that I forgot to connect a wire or so, but I could not find anything so far and now I don't know what to look for.

The car starts fine, but as soon as I release the key it stalls. If I just leave the key in "start mode" for a while, it runs fine, but it stalls in "run mode". I'm pretty sure that the engine gets gas, but it looks like it doesn't get any air cause the idle speed control does not work for some reason. I pulled fuse no 9 with the same result.

Is there anybody who knows what's going on here? That would be great, I have no idea what the issue could be.

Thanks,
Michael

[7THRTY2]

Michael,

I just went through something similar. It would turn over start for a split second then shut off. If I disconnected the coolant temperature sensor it would stay in for about 10 seconds. I went nuts over 7 weeks testing fuel pumps, fuel pressure, vacuum hoses, temperature sensors, ECU, FPR, ordered new spark plugs, cap, rotor.

After all that, it turned out to be the AFM. Plugged one I purchased on mye28 and she started up like nothing happened. AFM for our 733 is a 016.

*6/16. I also replaced the reference sensors, then swapped them, swapped main relay, fuel pump relay, checked for cracks in the boots. I didn't need to swap the idle control module (green box in glove box) but I was ready.

Hopefully it gets you closer to start.

Steve

[Kenneth1948]

Hey Michael, this post may not be a lot of help to you but maybe it will stir up some more responses because I think some of these guys who know a lot more than me probably know what the problem is.
I have owned and worked on several "big six" BMWs including an '84 733 like yours.
I encountered the same problem one time but I can't remember which car it was, don't think it was the '84 733.
Engine would start when cranking and stop as soon as you stopped cranking.
If I remember rightly, the fuel pump operates when the starter is operating.
When the car starts and you turn off the current that operates the starter then something else is supposed to control the fuel pump.
Problem is, I can't remember what the solution was, I don't think it was the AFM. Not that it's a bad suggestion, when the engine is running, the "door" in the AFM is held open by the airflow so the AFM knows the engine is running and controls several functions including telling the fuel pump relay to operate. Certainly would be worth carefully removing the AFM connector and making sure all the pins etc look clean and dry. If you can get your hands on it, spray some Deoxit on the plug and receptacle connections and re-install carefully.
I think the solution turned out to be simpler than than the AFM but it was a long time ago and I've worked on a lot of cars since. And I'm not getting any younger!
Maybe something like the main relay?
Some of you bright trouble shooters please chime in and help a first time poster! Good luck, John Kenneth

[Kenneth1948]

Michael, I reproduced this thread on the E24 board as I also have an '84 633 and I post there too. The '84 633 and '84 733 are mechanically the same.
You can connect here: https://www.bimmerforums.com/forum/s...-when-it-s-not!
Or, just go to the 7 series forum and look for my post. There are a couple of good responses there to this post as well as a few more comments from me

[7THRTY2]

Quick vid of my first no start, I'll add the video where the car started with the CTS disconnect. (Bad AFM)

https://youtu.be/bhdZH0m6yf4

[DesktopDave]

I'd definitely suspect the ignition switch. Could also be the ignition switch wiring connector plug on the lower steering column, if it was disturbed during the rust removal process. I think I have a spare E23 non-airbag column if you needed those parts to swap & test with, it's yours for shipping costs if it'd be helpful in any way.


There's also that little fuse inside the black "code" box that gets flaky causes trouble at times, it's in the driver kick panel if I'm recollecting the E23 correctly.


If it was a complete no-start (instead of what you have going on now), I'd also suspect the black/yellow "start" signal wire. It runs from the ignition switch to the starter small terminal, it likes to fall off. It also connects to the Motronic DME among other places. It runs all over, check the '84 733i ETM (electrical troubleshooting manual) for where it might have gotten cut or left unplugged.

[michael1234]

Hi,

Sorry for the late reply, I was busy with other things.

Actually the Motronic caused the problem, everything else worked fine. The problem is fixed and the car runs perfectly now.

Thanks!