Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #16  
Old 12-30-2021, 08:37 AM
jay_bob's Avatar
Control Freak
 
Join Date: Oct 2011
Location: Columbia, SC
Posts: 3,926
I think your gas tach must have been bad. If you try to plug a gas tach into a diesel 124 the needle will be buried above the red line at idle. BTDT

This is because the gas and diesel engines get their signal from completely different means.

Gas uses the ignition coil trigger from the distributor, so 3 pulses per revolution (assuming a 6 cyl).

Diesel uses the ring gear via a Hall sensor with 144 pulses per rev.

The ring gear signal goes to the EDS module which does rely on the OVP working. The car will run without the OVP, but you'll have poor idle control, and also the ABS won't work, as the ABS computer also uses this protected voltage source.

__________________
The OM 642/722.9 powered family
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)
2008 ML320 CDI (Older son’s DD)
2008 E320 Bluetec (Younger son's DD)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech
----------
gone but living on
1983 240D (body to greazzer, engine to t walgamuth)
Reply With Quote
  #17  
Old 12-30-2021, 09:21 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,549
Quote:
Originally Posted by Corvo Gold View Post
I now have a working tachometer in my stick shift 1987 300TD. The other day I got a wild hair and swapped the tach with a spare that came from a diesel w124. I think the inop tach that I had in there was from a gas model.

Either the tach itself was broken or there is a difference between diesel and gas tachs.

FWIW.

Corvo Gold
1987 300TD, converted to stick shift
Where did you mention this was a gas conversion? How did a gas tach get in your car, and how did it work before the manual trans was there with a diesel motor?
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
Reply With Quote
  #18  
Old 12-30-2021, 10:13 PM
ykobayashi's Avatar
Registered User
 
Join Date: Jun 2005
Location: Irvine, CA
Posts: 1,157
Thanks for following up. Great you got it going. The diesel tach operates on a hall sensor. The gas probably works off the ignition coil. I bet the gas wants to see a higher voltage than the diesel tach.
__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
Reply With Quote
  #19  
Old 07-27-2022, 09:25 PM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,224
anybody know of a source for a wiring diagram for my 1992 200
td? The AC quit working and we cannot find the wiring piece by piece.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 06:27 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2022, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page