PeachParts Mercedes-Benz Forum - 300E m103/w124 accelerator sensors

PeachParts Mercedes-Benz Forum (http://www.peachparts.com/shopforum/)

- Tech Help (http://www.peachparts.com/shopforum/tech-help/)

- - 300E m103/w124 accelerator sensors (http://www.peachparts.com/shopforum/tech-help/284605-300e-m103-w124-accelerator-sensors.html)

Quote:

Originally Posted by Californian SE (Post 2544725)

assuming i am testing the correct plug (the ONLY three point adaptor on the front of the fuel distributor pump) then the top, is 0v, the middle fluctuates between 1.1 when idle - to 1.4 when accelerating, then .9 when taking your foot off. and the bottom (which I thought should be 12v) is only 4.76 v.

now Im just confused.

Air Volume Meter Sensor:

Engine idling:
Terminal 1-2 should read 0.57 to 0.81V
If voltage is higher or lower you need to replace the air volume meter.

Engine off, ignition on.
Slowly deflect air flow sensor plate.
Terminal 1-2 Voltage should increase from 4.6-5.1V

Ed A.

so there is infact a sensor on the M103 intake?
either way, the voltage between 1 and 2 is .73 and between 1 and 3 is 4.76 so i guess it's back to the drawing board!

on a side note - occasionally the aircon fan kicks in (radiator fan) when starting but goes out after a few minutes.

idling perfectly now too...

Quote:

Originally Posted by RBYCC (Post 2545038)

M103-12V uses KE-Jetronic III CIS-E.
No potentiometer to monitor throttle position.
Just a simple SPDT switch ( wiring diagram reference S29/2 which plugs into X56 ) that merely detects full load and idle.

RE:Service Manual Engine M103 S-2421-103, page 07.3.11 I-121/24

The "potentiometer " is the air volume meter sensor ( wiring diagram reference B2 )

Ed A.

Sorry Ed, you apparently missed my point. I wasn't referring to the S29/2 throttle valve switch, which does indeed detect idle/full load throttle positions (along with the decel microswitch S27/2). I was referring to what the FSM variously calls the "air flow sensor potentiometer" or the "air flow position indicator". That's the B2 component. It essentially does the job that a mass airflow sensor does on later motors and, although it technically measures airflow, it serves as a proxy for throttle position. More throttle, more airflow. Less throttle, less airflow.

Quote:

Originally Posted by Cal Learner (Post 2545545)

Cal, not a problem..I just wanted to clarify your statement:

"Potentiometer. On the front of the throttle body, measures the position of the throttle. There is a resistance test in the FSM, but I don't recall it offhand. Won't be hard to find under the electrical troubleshooting section, if you can put your hands on a copy of the FSM "

You referenced the device on the throttle body which is merely a switch...
The variable device is on the air valve / fuel distributor assembly...

Didn't want the OP reading the wrong device !!!