My sisters ML320 has a problem starting up, it cranks but doesnt fire up, i recently replaced her battery, is it possible i needed to reset something or is that the sign of a bad starter,it does the sound like its going to start but it lingers and does not ignite
. thanks amigoes!

Joro,
Same thing happened to me a few months ago after a complete battery drain (my wife left the ML's lights on for about 24 hours). After I put in a new battery the vehicle would crank but not start. If you have an extra key try to start it with that. My 2nd key worked fine. Something to do with recognizing a security code from the key. It is explained elsewhere in the ML320 forum. Hope this works for you.
Ken

__________________
2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)

So is there a way to reset the key, were you able to use the other key afterwards?

AAM failure could be the cause. The drive authorization system was integrated with the AAM in pre 2000 models. AAMII, however, has a separate module for the DAS, enabling you to replace just the DAS, which is the actual culprit. Later models displayed a 'start error' on the dash when this happens. The problem will eventually toast all your keys. With a DAS replacement, the keys should be able to be programmed into the new DAS. There is a service bulletin on this issue but it's not at my fingertips right now.

I agree with the possible AAM problem. There may be another issue to consider. I didn;t see what year model you are referring to. Nonetheless, early models had a fuel pump design issue. You drive to theater, gas station, in-laws, home(those were our destinations)...Turn off the car. Get back in and try to start. The engine would crank but it would not even act like it wanted to start. We were informed that was a fuel pump OVERHEATING when the gas level went below 1/4 tank. We had 4 fuel pumps replaced in the first year model ML. On the 5the failure, we traded it in under lemon law provisions.

One cps sensor fixed this ML, thanks gang.
J