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1991 300E 3.0
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148 Posts
Discussion Starter #1
On the AutohausAZ site, they list two Crankshaft position switches. Front and rear.
1. Are there two CPS?
2 Do they plug into the ignition module on the driver's side inner fender well?

I bought both of them. On my car, the one in front plugs into the ignition module. But it uses the plug that came on the rear sensor that I bought from AZ. But the sensor does not look like the one I've seen you guys referring to.
The sensor for the rear looks like the one you guys are switching out, but I can't find where it would plug into.

Are California cars that much different? Does anyone know the part numbers for this CPS? And are there two of them?
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
Yes, there are two crankshaft position (CKP) sensors.

The one at the back of the block (behind the oil filter) is the one used by the ignition system. It has a coaxial cable that runs the whole length of the engine wiring trough and then goes to the EZL module on the fender ahead of the strut tower. This sensor has a coaxial plug at the EZL module, kind of like a big RCA connector.

If this CKP sensor fails the engine will not start or run. If the engine is already running and the sensor dies the engine will quit.

The other CKP sensor is referred to as the TDC sensor because that is the only info it provides. It bolts to the timing cover and is exclusively for diagnostic purposes. Its wiring runs straight to the round X11 connector near the EZL module.

IIRC the wiring for the TDC sensor ends in an oblong or kidney-shaped 2-terminal plug that slides into a recess in the underside of X11.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,822 Posts
The two sensors are properly A) cam position sensor B) Crankshaft position sensor. The cam sensor is the one on the front of the motor. The crank position sensor mounts on the bell housing in the area under the oil filter mount. It is held in place by one 10mm bolt. Easiest to get to from under the car. The "plug" end of the sensor connects to the EZL mounted on your inner left fender. Routing the cable is a bit testy.

Use the search function for "Crank position sensor" and you'll find images of it's placement.

Jayare
 

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Registered
1991 300E 3.0
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148 Posts
Discussion Starter #4
On my car, the cam sensor is the one that has a large RCA looking connector. On the Cam Sensor I got from AZ, the electrical connector is an oblong, three pin connector that cannot be plugged into the EZL Module.
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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Cam sensor?

I thought we were talking about the crankshaft position sensor?
 

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1991 300E 3.0
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148 Posts
Discussion Starter #6
I used that term because Jayare used it.
The "Front" sensor that picks up the signal from the front pulley is the one that looks like an RCA plug, not the rear sensor. But the sensors I was sent has that RCA type connector on the rear Sensor.
 

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1991 300E 3.0
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148 Posts
Discussion Starter #7
O.K. Here is a picture of the ignition module that came out of my car, along with the new sensors.
The front sensor looks like the one on the right (Just as it should). But has the same connector as the rear sensor. It plugs into the right lower socket of the Module.
[/IMG]
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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The part on the left is the CKP sensor that mounts at the back of the engine. It plugs into the socket on the bottom RH corner (as shown above) of the EZL module.

The other sensor is the one that mounts at the the front of the engine and has nothing to do with injection or ignition. I remembered that it had a kidney-shaped two-terminal connection. In fact it has a kidney-shaped 3-terminal connection. But it does plug into the *underside* of X11.
 

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1991 300E 3.0
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148 Posts
Discussion Starter #9
But not on my car. On my car, the front sensor has the coax plug that most of you have for the rear sensor. My car does not have a front sensor with the kidney shaped three terminal connection.
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
Um, okay, then your car is beyond my experience.

I can't find anything online about a difference for CA emissions-equipped 91s but that's my best guess.

Let us know what you find out.

Come to think of it, ask Lowesguy what his CA 300E is like.
 

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Immoderately Caffeinated/ Vintage Moderator
T5
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17,188 Posts
Hey Ned, If your engine is M103 the crank sensor lead (big one on left) plugs into the bottom right connector. You say the other (front cam sensor) does not have the kidney shape three terminal? The one in the pic is the correct one for your car.
 

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Registered
1991 300E 2.6
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12 Posts
O.K. Here is a picture of the ignition module that came out of my car, along with the new sensors.
The front sensor looks like the one on the right (Just as it should). But has the same connector as the rear sensor. It plugs into the right lower socket of the Module.
[/IMG]
Thanks !!!
A picture is worth a thousand words!!
Now I know what I'm looking for. I had replaced the front one thinking that was the crank sensor. I hope the back one fixes my problem of the car stalling when the temp. gets up to around 90 to 95 deg. C.
I always have to wait about 5 minutes until it cools to restart. As long as I'm moving and I'm getting airflow I'm OK, as soon as I stop and the car heats up, it stalls.
(1991 300E 2.6)
 

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Immoderately Caffeinated/ Vintage Moderator
T5
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It could also be the fuel pump relay. Before you start spending money, carry a multi-meter with you and next time it stops test the resistance at the EZL connector of the CPS. It should be between 650 and 1200ohms. If it says zero it's deadish. You'll still get a reading when it's cold.

In my experience if it's the cps it wont start again til the next day.
 

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1991 300E 3.0
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148 Posts
Discussion Starter #14
Thanks, I'll try that. I haven't had a chance to tear into it yet. Hopefully this weekend.
 

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1991 300E 3.0
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148 Posts
Discussion Starter #15
I pulled the crank sensor this weekend only to find that the hold down bolt was loose. Does the sensor need to be grounded? If so, that could've caused the intermittent no start issue.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,822 Posts
I pulled the crank sensor this weekend only to find that the hold down bolt was loose. Does the sensor need to be grounded? If so, that could've caused the intermittent no start issue.
It isn't a ground issue as that is taken care of when the sensor is plugged into the EZL. However, a lose sensor would very much be a no, no. Make sure the sensor is secure and keep a meter with you as suggested.
 

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1991 300E 3.0
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148 Posts
Discussion Starter #17
Well, the car actually runs better and has never pulled harder. Of course, that was 17 hours ago. Now the head gasket just turned into an emergency instead of just a must do. I came back from lunch and the upper hose practically blew off. So I am now assuming it is leaking from cylinder to coolant chamber. I will attempt to limp it home and start the Head Gasket job.

Follow me in my next adventure in the title roll of the new upcoming DIY titled
"M103 Head gasket questions" :surrender:


The Germans hate me...
 

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Registered
1991 300E 2.6
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12 Posts
Mine has a round head bolt with an allen key slot in the middle, looks like as 5mm or 5.5mm allen,
WHY COULDN'T THEY HAVE USED A REGULAR BOLT HEAD!! I've spent hours trying to get this thing out with no luck, the slot for the allen key is worn out, all allen keys slip in the whole; any suggestions??
 

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Registered
1991 300E 3.0
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148 Posts
Discussion Starter #19
Mine has a round head bolt with an allen key slot in the middle, looks like as 5mm or 5.5mm allen,
WHY COULDN'T THEY HAVE USED A REGULAR BOLT HEAD!! I've spent hours trying to get this thing out with no luck, the slot for the allen key is worn out, all allen keys slip in the whole; any suggestions??
It is a 5 mm allen bolt. The trick is to get a torx drive bit that is the same size or just a bit larger (And I mean only a bit larger) and tap it into the allen hole somehow (it's a very tight squeeze getting any tools into that area. You might have to pull the oil filter and the starter) and turn slowly but firmly.
 
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