ashan05

Merry Xmas, Ladies and gentlemen! I'm about losing my mind despite all the embarrassments I've received from my master - my car. It's obvious I'm not going anywhere this xmas. It began having problems to start, and sometimes stop in a traffic light. I was told it was the alternator, then I changed it. Now the problem happens randomly; I would drive it around the world smoothly and then come home safely and park it. It would refuse to start when the temp is about 20-25 degrees the next morning. It would crank on its own and all powers are on. I've changed the starter before, and battery too even the EGR valve and stater. Now as I'm writing this, it already happened this morning. As soon as the sun comes up, it will start. I took it to the dealer mechanic and left if for days but they couldn't find the issue. There's no check engine light either. I've checked the fuel pressure and it's okay. The mechanic is suggesting that it may be a crankshaft sensor, but no proof. This is a 1998 ML320 Benz. V6. All is left is for me to walk into the MB dealer store this time and pay 100 bucks and have it diagnosed. what do you guys think? Have anyone experienced this before?

Maj. Dundee

It is the Crankshaft Position Sensor. It is cheap enough to buy and replace to end your problem. It is located on the driver's side of the engine, as seen in the photo.

Remove the connector and check whether or not you have one or two raised portions on the sensor and order appropriately. Autohaus has both.

http://www.autohausaz.com/search/pro...ition%20Sensor

MinnBobber

Maj Dundee,

Would that likely be the case with my 2005 ML500 SE which starts worse in the cold (I'm in MN)? 60,000 miles on it.
Autohaus has that V8 crankshaft position sensor/plug too, says it's at back of engine. Do you know where/easily accessible??
Mine starts worse on cold mornings, might crank 2+ seconds before starting. Starts better IF turn key to ON for a few seconds, turn key off, again turn key to ON for a few seconds and then START. Has always started instantly, prior to this.
What do you think??
I have ordered previously from AutoHaus and service was great from them!!

Any help greatly appreciated!!!! Thanks

Bob in MN
Now with cold weather my "hold the hood open struts" seem to be going out. Normal for 60K miles?

Maj. Dundee

From what you are describing, it doesn't seem to be a CKP Sensor, but a fuel problem.

Change the filter first and if there is no improvement, then you will probably need a new fuel pump.

MinnBobber

thanks Maj Dundee.

I suppose the plug in diagnostics do nothing to help determine what exactly is off ( fuel filter or fuel pump)as nothing is completely bad.

If it's the fuel filter/ pressure regulator combo, would it be that the regulator is bleeding off too much pressure, leaving not enough PSI at startup OR the fuel filter is clogged/restricted??
I looked up the maint schedule and the fuel filter/pressure reg is scheduled for change at 60K miles. I'm only at 61K miles.

Any way to tap in and measure fuel psi at the fuel rail --to help diagnose?
Bob

Maj. Dundee

Diagnostics cannot determine fuel pressure. It can only be check manually with a fuel pressure gauge.

The fuel filter with its pressure regulator can be at fault, or the filter is partially clogged restricting flow during the priming stage and that is why that should be changed first. But there is also a check valve in the fuel pump.

In any event, you should always change the filter when replacing the pump, so try the filter first and then if not, the pump.