GC4E320

I was going to work this morning, came to a hill where light is and engine just quit. Since I was heading down the hill, I was able to get the car off the street and into a parking lot. I put it into park and restarted; went on to work without problem. Shows no malfunctions but I haven't been able to get to an Autozone to get codes read.
Is this just a random thing or am I looking at a crank position sensor problem? I recently replaced the core of the Mass Air Flow sensor (about 10 days ago) with a BOSCH one, and this is the first problem I've had since. My gas mileage has increased with the new MAF and the pickup has improved also. Is there a correlation here?
Help! I don't want to get stranded. What do I do if this happens again and it won't restart (Other than call a tow truck)?

csumt76

If it is the crankshaft sensor, you should be able to get it restarted next time by waiting for the engine/sensor to cool off. I guess you could use the water hose at the gas station to speed up the process.

benz300

I suggested get that crank shaft sensor changed. most of the E class suffer from that problem. strangely there's no error messages when it starts to malfunction.

GC4E320

Thanks for the suggestions. This morning it wouldn't start at all. It cranked, no problem, but it won't start.
Two days before when I started it up, it seem to 'hang' in the start position so that the starter continued to turn over. I'm not sure but I think that the key didn't go back to the run position as it should. The Check Engine light came on for a day then went off yesterday.
Worked fine on the way home from work yesterday evening (and I had several places i went to on the way so i started it several times).
on a normal car, I would suspect the fuel pump but, as I've found out, the MB (especially the E320) isn't a normal car.
With 90000 miles on it, should I expect this? What does it seem to be? I can't get it to an Autozone for a code check so I just had to call a repair shop.
Help!

csumt76

The reason that no malfunction is displayed while you are driving and the engine simply dies, is because the crankshaft position sensor is simply an input to the control module which it uses to calculate rpm.

Here it goes.... Insert key in ignition switch, EIS takes/processes key data by infrared signal, key is authorized.. bam steering lock is disengaged, turn key to position 2, tip key to start position and release, start request sent over CAN, ME acuates starter via relay, starter disengaged once RPM jump is seen from the engine firing, engine running signal comes from the generator(circuit 61).. I know thats a little off topic but....

In this process if the crankshaft sensor is faulty(sees 0rpm), it will not attempt to fire of even inject fuel because it thinks the engine is not turning over.

So, similarly, if you are driving down the road and suddenly the windings in the CPS go open all ME operations stop!! Its not going to dump fuel and spark into an engine that it does not think is rotating.

I would bet money on your problem being the crank sensor based on all of your descriptions. The check engine light can come on when the ME see's erratic readings, the code will always be a stored fault and the light will go out once it sees it working again.

Cam sensors fail occasionally, but generally always have fault codes/check engine lights and cause hard/no start. The thing with the CAM sensor is, if you disconnect it the engine will still run on preset timing tables within the control unit.

Also, the engine will run without the airmass based on calculated values like a speed density system.

The crank sensor will run you over $100 from the dealer, but is simple to replace.