Hi all,

This is my first post here, but def not my first Mercedes. Quick background, I have a 66 W111, 72 W108 4.5, 99 w202 kompressor, 02 ML500, 89 w201 2.6 and my current problem child, a 87 w201 2.5 turbo diesel. If you guys follow Mercedes Benz on facebook, this is one of my Mercedes https://www.facebook.com/photo.php?fbid=845375622157135&set=a.177452518949452.45847.112336898794348&type=1&theater I purchased the diesel from an individual who had no idea on cars nor Mercedes, the car was very poorly taken care of and has its fair share of rust at the all so common jack points. I scored a decent deal off it, and am in attempts to bring it back to life.

So, I have a couple of issues...first off, while running, when you give the car gas, the entire car shakes as it drops back to idle. I am unsure if its a fuel delivery issue or motor mounts. I have put a diesel conditioner [no idea how long the car sat as the person wasn't very fluent in English that I purchased it from]. The only thing I have done so far is replaced the clear inline filter to the diesel pump. I am waiting [from pelican parts ] for my replacement parts in which it includes the diesel fuel filter along with some fuel lines. Even after replacing the inline clear filter, it seems to have alleviated it slightly, but still have the hard shutter going back to idle and a very hard shut off. I will also mention that the oil is way over filled [waiting to change the oil for when my parts come in with the new filter].

My second issue is that the tach in the cluster didnt work. I had a spare laying around but it came from a 2.6, the red line is obviously different, but I was thinking that it would still work? When installed in the car, it jumps immediately to 7k [its max] and when you hit the gas, it drops. Bad ground? Original and replacement gauges bad? Also, the oil pressure guage reads at max at idle and drops when you rev the engine, again, bad ground [or possibly related to the oil being overfilled]? The oil pressure, gas gauge, both drop with revs, however this gauge is original to the car. I honestly cannot say if i can recall if it did this before the tach change.
Any insight would be most appreciated, I have tired my search and havent found much related to my current issues.

BEFORE you run the OM602.962 again !
Too much Oil Allows the Crank to dip into the Oil and Aerate it.
(Think Milk Shake, Instead of Lubricant)

You've self Diagnosed the most likely cause of the Gauge (s) Problems...
Bad Ground(s) at/between the portions of the Instrument Panel.

member cooljjay opines correctly:

"I believe they all share the same ground....being the instrument cluster....there are 2 bundles of grounds.....also did you exam the ends of each fuse and make sure they are intact....it is wise, if you haven't done so to replace all the fuses with ceramic body and either copper or brass filaments..."

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'84 300SD sold
124.128

Thanks for the response! Yeah, I knew it wasnt good for the engine with the oil over filled, the wonderful PO had it filled around a 1/4" above the max line....smh, but i just needed to move the vehicle around a couple of times. Regarding the fuses, i have checked them, they all seem ok and intact, but they arent copper, unless they are corroded that badly, I'll pick up some more tomorrow. I'll hit the grounds tomorrow as well.

But I should be right to think that it a tach from a 2.6 should still work on the 2.5 regardless of its redline marking on the face? I dont care if the line isnt correct, i just want the tach to work, I can replace it with a correct one later.


thanks for the link, however nothing comes up.

Ok. Put the tach back in, your gas tach won't work here. You have a problem with the overvoltage protection relay. This is sort of a surge protector, which usually causes as many problems as it prevents. Among the things that it controls are the EDS system, which controls idle and sends the engine speed signal to the tach. THE OVP is located behind the battery. You need to remove the weatherstrip under the windshield and the plastic divider behind the battery. It's usually an aluminum can with a red top and a fuse in the top. Replacing it should clear the problem up.

I do think your best bet is to drain and replace all fluids, just to bring things up to standard.

Ah yeah, i forgot about the OVP, i have a bunch of spares laying around. Ill check that guy out tonight. Yeah I am doing a complete flush this weekend of all fluids, Im just waiting for my shipment of parts to come in that I ordered last week. Thanks for the response! Keep you guys posted.

ok, so im assuming since its diesel the OVP cap is black, i did happen to have an extra one on hand, i tried them both, no change for the tach jumping to max when the car fired up, the old one didnt even move on either OVP. Fuses in the relay were good. Guess im still going to be trying to figure this one out.

Here are the diagrams for EDS. Be aware that EDS is only used on the 1987 190DT. The wiring diagrams are unique to this car...don't get confused by using regular 2.5 schematics, and there are differences in plumbing from the 300D 2.5T. Your engine is a 602.961, not a 962.

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That's a function of "Peach Parts" (It doan likee Links)

Ceramic Copper fuses don't look "Copper-ish" because the Copper is coated
with "Tin" to reduce Corrosion.

ALSO , Always remember the FUSES May have Micro-Cracks that YOU can't
see. So, ALWAYS test for continuity with a multi-meter!

So.. try this link:

Do an "Advanced Search" on this website using "jeremy4568"

jeremy4568 is an E.E.

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'84 300SD sold
124.128

Thanks for the diagram, there were def two wires joined into the fuse box from the top which i know arent supposed to be there, I took them out, but of course have no clue where they go at the moment.


Link still isnt working, haha

Well, if I have some time tonight, i will try and check it out, i have to do the steering rack boots tonight on my ML, thanks again for all the responses, till the next tinker!

the other thing i forgot to mention, is that the outside temperature readout display was trashed, i replaced it with an extra one i had, it it reads like 16 degrees F outside when its around 80, anybody have any insight to this? Busted gauge?

Sounds like the bumper sensor is damaged

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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 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

There are only two parts: the display and the sensor. It sounds like your sensor is bad. The sensor is located behind the license plate. You would think that it just plugs into the harness and would be a quick thing to replace, but no. It's hardwired to it's own harness, which has to be threaded all the through the engine compartment and through the firewall to the dash. At the firewall, you have to disassemble the connector to work it through the grommet. It's a pain. Unless you really, really need to know the outside temperature, concentrate on the more important stuff for now.

yeah, its def not on the top of the list, just wasnt sure if there was any off chance that it was related to the current issue with the cluster. Didnt have time to mess with the diesel tonight, got the boots done on the ML, and just also realized that the motor mounts on the white 190 are shot on the way home as I can shake the whole motor with my hand...the list never ends, gotta love these old Merc's, wouldnt trade them for the world though

Does it say F or C? I only ask because 16 Celsius is about 60 F. A nice day is around 20 C or so. My 93 190E displayed in F but my 84 190D displays in C. Mine isn't very accurate either, and I ignore it. I deleted the display in my sister's 190D because the cluster housing I installed came from a Euro 2.0D and didn't have the spot for it.

I guess if you have a perfect garage queen car, the display might be of concern. Most of us have bigger fish to fry though. That's the way it goes most of the time...

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
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When you replace the motor mounts, inspect the front of the oil pan. With the 2.5, the engine settles onto the swaybar when the MM's collapse. You can wear a hole in the pan if it goes on too long.