Hi all,

Just had the second episode of having trouble trying to start an M50 powered e34 after the fuel had been run out.

In both cases
- I'd parked on a slight slope, left the car and then been unable to start after being away for a while.
- the fuel was critically low.

After adding fuel, as much as 9 litres, the engine would not start after prolonged cranks/cranking. I even tried jacking the car back to level.

The solution?

1. Remove the fuel relay (the middle, 4 prong one on M50 (vanos and non-vanos) engined 520i and 525i e34, possibly M20, M30 and e36, e46 and e39/M52 as well), jumper the high current wires (#87 and 30) and listen to the glorious sound of fuel gushing through the engine's fuel pipes and purging the air.
2. Start the car (even more glory; immediate vrrrroom!)
3. Remove the jumper and re-sinsert the relay with the engine running.

When cranking one may not be able to hear the fuel in the pipes but it was very loud. I doubt the pump was running at all when cranking previously.

But the question is why?

I'd cycled the ignition several times before cranking
Did a few cranks, not just one long burst
Left up to 10s between cranks, some with ignition on

The ECU has to initiate fuel. As I understand it, it will do so if

- the engine is rotatating (cranking or running), (ie. input from the cranks position sensor required)
- the crash relay is not triggered
- the trans lever is in P or N (if auto), or clutch depressed if manual (though maybe not all, mine does not have this feature)

So Dear Bimmernut Boffins; Why?
Is there some fuel system pressure check that is falsely positive?

Cheers! Nick