Any advice is welcome, the dealer has tried twice to fix the problem with no luck.

My wife's ML320 (2000) occassionally won't start after she's driven somewhere and parked it for about an hour (45-75 minutes). When we turn the key, it cranks ok, fires for about half a second, and dies (and gives a 'start error' i think).

If we keep trying to start it in this condition, it seems like we burn out the key
after a while, and get 'start error' on the dash display, and that key cannot be reprogrammed by the dealer, we have to order a new one.

If we wait an hour or two, or sometimes if we remove the gas cap, then it starts and runs fine. During the winter, we never have this problem.

We've had this happen about 10 times, and twice we've burned out both remote keys (probably because we tried both keys many times).

Is a key likely to burn out if you try and start the car 30 some times in a row in 3 minutes?

Is vapor lock something I should be thinking about, and what's a good solution?

Rich

It sounds like maybe it's a crankshaft position sensor problem but certainly the dealer would have known to check for that.

the dealer replaced the crank sensor somewhere in the middle of these other problems. The car would crank for a full 10 seconds, and not start.

The current problem is that it cranks for about half a second, actually fires and rev's up a little, then dies. And the 'start error' message appears before the RPM's go to zero.

The transponder ring (security ring) on the steering column may have been bad. It happened to me few years ago. The truck won't start or it will start (engine runs) and dies right away. The dealer had to replace that twice. After the second replacement, I have not had a problem with starting. Please don't let the dealer replace your keys too frequent, you only have 8 to play with, sounds like you've lost 4 already. Beware, the AAM is not cheap to replace after you hit the 8 keys limit.

__________________
98 ML320 (gone but not forgotten)

that is my guess too

Have you had the updated fuel filter and lines done yet? This could also be the problem.