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

It's pretty easy to check fuel pressure if it stalls and won't restart, you'd need to have the brass cap loosened, or bring a wrench along, and carefully press on the end of the Schrader valve and see if fuel comes out. I wouldn't doubt the CPS also, but it's good to have more than one idea,don't restrict yourself to one course of action.
Gilly

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12 pack, you're not very sure are you? i was thinking more along the lines of a micro brewery. but thanks again for all the help, stuck a new sensor in and we'll see what happens 9in the future.thanks gilly i've checked the psi w/ the schrader valve previously. hope you all have a wonderful weekend.

Eh Gilly, won't the ECU shut off the fuel pump completely if the CPS (L5) is not recognized? Making the fuel pressure check inconclusive between pump and sensor?

I don't believe the engine control unit has a part in this, no. I'd have to look it up, but I believe it just works off the AAM with no input from the engine control unit. I'll try to find info on this later, it'd help if I had access to WIS, but I don't.

Gilly

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This post has very useful info. Our 2000 ML 320 just shut down without warning night before last. It would turn over but not start. Most indications here seem to point to the crank sensor as the culprit.

Today our dependable independent confirmed this. No codes were showing in the system so he let it run for about 15 minutes monitoring the read-out (note that it started when cold) and after it warmed up he started losing readings from the sensor like the RPM etc. then it stalled.

He installed a new sensor and it has been running fine for about 45 minutes. Seems to have been a textbook case. This forum is great.

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John Myers
500SL
300CE
260E
240D
190E
190E-16V
ML320 (2)
280CE (2)
SLK 320
SLK 230

I believe the determining factor in which part has failed is if there is spark or not. The ECU controls the fuel pump and turns it on if it senses crank. If the CPS has failed, the engine will crank but produce no spark or fuel.

Spark but no fuel = fuel pump failure

No spar and no fuel = CPS failure

Correct me if I'm wrong.

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)