Mercedes Diagnostic tools 300E 1988-90

In my manual, it shows two tools. One that reads pulse-
codes, the other that reads on/off percents (a meter).

Can I fab both of these? The code reader looks like
an LED, switch and resistor (if I had the schematic)
simply wired in a fancy box. The on/off reader a plain
voltmeter (12v scale?) What functions are the pins in
the X-92 and X-11 connectors?

Or if they are inexpensive (riiiight!) can I buy them
from MB or after market?

Bob Hoenes
rhoenes.ee66@gtalumni.org
770-422-0081
1989 Artic snow White 300E

[JimF]

The on/off ratio (lambda) tester can be purchased from the following link: http://www.technictool.com/m0039%20m126-0521.htm

The FAULT CODE COUNTER (124-1921) can be had by making one yourself or buying one from this link: http://www.baumtools.com/english/specialtools.cfm?CN=3

Also read Steve's article in the DIY section.

[Arthur Dalton]

Bob,
I sent the schematic to the alumni.org addy.
Arthur

The "on/off ratio" as you call it is called duty cycle. You can buy a digital voltmeter with a duty cycle function at Sears for 29.95. I happen to be in on a 10% off all Craftemen tools day and bought it for even less. It works great.

Most likely you will connect and find a 50% duty cycle. There are only a few other codes which may be trapped.

The pulsed codes are only on California vehicles for the models you listed.

Have a great day,

In the X-92 connector, my 300E only has pins 1, 6 & 7.
NO 2, 3, 4, 5 or 8 (empty holes/no wires!) Where does
the code reader connect???

And on the X11, what scale do I use on the duty-cycle
voltmeter, and to which pins in the X11 do I connect it???

Thanks,
BnObob
rhoenes.ee66@gtalumni.org
(East coast MB 300E)

[stevebfl]

Have you read the article in DIY?

I don't know about the X92 connector. The two possible diagnostic sockets are X11 and X11/4 I think (being without diagram). The only one most cars from 86-90 is the one on the driver's fender.

In it, on pin# 3 the duty cycle (integrator) can be read. To ask which scale infers that you don't understand duty-cycle. It is a percentage.

I read the DIY, and on a scope, duty-cycle is obvious.
But in a meter (modern-new-fangle-ones-with-chip) it can
do the area integration under the square wave, and print
out a percentage. But there still must be some max voltage,
less the meter becomes fried if it is hit w/ giga-volts.

Years ago w/ galvanic meters (iron core, needle stuff) we
could set the thing on a A/C scale, and the bridge inside
would integrate the areas under the curve for the + and -
voltage swings. If the cycling was fast enough you would
get a ratio, and a needle swing. But if it is a wave from
(say 0 to 12v dc) then this Rube-Goldberg will not work,
and you truly need the new (intellegent) meters, or a good
old fashion O'scope.

And I did put an LED across a pin in X-92 and read a code
of "12". But my Chilton book only has codes for the M103
engine to 10. Is there a list of codes somewhere within
this MercedesShop, or Forum????

Thanks!

Brothers of The Benz,
If you read the Service manual you will note an option value.
It is degrees in dwell.(21-27 degrees dwell)
Using a points ignition dwell meter you can establish the mixture control for the proper O2 voltage and smooth idle.
It's in The Book.
Service Manual, Engine 103
Section 7.3
Job 100/2
Happy Trails Beep Beep from The Spiderman in Houston!!!