300E m103/w124 accelerator sensors - Page 2 - PeachParts Mercedes-Benz Forum

RBYCC · #16 09-15-2010, 10:50 AM

Quote:

Originally Posted by Californian SE

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.

Californian SE · #17 09-16-2010, 05:24 AM

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...

Cal Learner · #18 09-16-2010, 06:39 AM

Quote:

Originally Posted by RBYCC

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.

RBYCC · #19 09-16-2010, 09:32 AM

Quote:

Originally Posted by Cal Learner

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.

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 !!!

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode