owner says its done it 5 times or so.the mas air flow sensor has been replaced.any hints on what it could or has someone had this before.We couldnt extract any codes from it.thank you

Try the Crankshaft Position Sensor (CPS).

MLs are notorious for this.

Search and see my previous posts on subject.

Dickie
00 ML 320
97 328i

Yes, crank position sensor is the most common problem with that symptom on that vehicle. Fuel pumps also go out like that on the Ml 320's but usually set a code. If no code -go with the crankshaft position sensor.

I'd agree with fuel pump, and also the fuel pressure regulator, which is part of the filter assembly. Lots of owners are failing to get the filter replaced because of the expense (retrofit required to large filter) so the regulators may be failing now. Also check the pump electrical connector for corrosion, it's in the left rear wheel well, where it's prone to crud.
Gilly

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thank you everyone i'll try the cps and sees what happens.ive looked throughout the your archives gilly and the same thing happens with this one, the intermittent stalling, sometimes it will fire sometimes it wont.it got towed here after not being able to start but it started fine when i tried this morning

Thats where I would start and bet a 12 pack thats your problem.
Been there, done that.

under $75 Fix.

__________________
Steve Danville
what i did myself.
CPS
rear shocks
MAS x 3.
SparkPlugs (twice)
Fuel pump & Filter
Window switch
replaced both failed horns with Honda horns.
Cleaned ERG Tube
Oil changes
Oil consumption Fix
Brake Pads
A/C Recharge
Anti-Freeze change X 2.
Front Shocks. Monroe. $90
Mercedes Warrenty Work:
Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s
Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles