I use one that IS factory.(and stealth!)

1. Take an old fuel/temp/ oil pressure/economy gauge section from a GASSER 126 and transplant it into the 126 diesel instrument panel!
2. Remove needle from economy gauge (remove STRAIGHT up).
3. Replace needle on the ultra thin gauge shaft from where it came, but place it with the needle pointing at ~10:00 o'clock position.
4. Rotate the needle CC and lift/ bend it over the left side stop pin.
5. What used to be the economy gauge (Bourbon type vacuum gauge) is now a boost gauge (Bourbon type pressure gauge).
6. Attach with appropriate hose to "T" in boost line or to the empty intake manifold fitting.
7. I attached the hose to an aquarium gang valve in the boost line to the overboost protection switch so that I could rig a parallel hose and shop gauge temporarily into the cabin in order to calibrate (by moving the indicating needle on the shaft of the former economy gauge).
8. Full travel (left to right) is ~16 psi after calibrating. (I run ~14psi full out uphill). FWIW

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Any tips to removing the needle? I can't get the bugger to budge.

The shaft that the needle hub is pressed onto is very thin, so "straight up" removal is important. I use pliers with tape on the jaws now.

Two spoons (with tape on the undersides) as "pry bars" on the needle hub have been used with success.

Be careful, but strong, and good luck.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Will that 126 gauge pod work with a '90 124 300D? Or are the electronics for the fuel/temp/oil pressure different?

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Dale

http://i52.photobucket.com/albums/g1...MG_2277sig.jpg

1990 300D 2.5 Turbo -155k
2000 E430 - 103k
2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k
2014 VW Passat TDI SE - 7k Bro's Diesel
2006 E320 CDI - 128k Pop's Benz

Pre-glow - A moment of silence in honor of Rudolph Diesel

That is way smart!

Do you have to use a gasser gauge from a same year car or are all the W126 years the same in this regard? I'm thinking about all the connectors on the back.

Also, I have a KKK turbo on my 1983 300SD - the archives seem to suggest that boost adjustment is much easier than on the Garrett - any thoughts? I assume I run my vac gauge connected in series with the vac line from the manifold to the overboost switch-over valve when setting it up?

I think that connection would be in parallel, wouldn't it? Also, it seems to me that the best place to connect a boost gauge is between the switchover valve and the ALDA. The following is a verbatim quote from a Mercedes technical service bulletin:

07.1-85011 Poor Engine Performance Engines 617.95 Revised 10/85 1/85

Cause:
Low boost pressure at the boost pressure aneroid caused by soot-in the switch-over valve, boost pressure lines and hollow screws on intake manifold or boost pressure aneroid.

Remedy:
Check, clean or replace parts as required.

Always check boost pressure directly at boost pressure aneroid or at the boost pressure line just behind switch-over valve. If necessary, bypass switchover valve and repeat test.

That makes sense - between the switchover valve and the ALDA - guess you see what the ALDA is seeing that way.

As for parallel or series, I guess I just interpose a T-connector in that line and run the third leg to the gauge, no?

In here?

Attached Thumbnails

 

Thomas, don't know all on the gasser gauge on the 86-89 revision; 90-91 revision. There are slight differences in the 126 for ea. of those time frames. I used a 1984? 380 SEL gauge section from the '81-85 time frame version of the 126. I have seen many others and the method (armature winding) and resistors of the fuel gauge part do look a little different on some of the newer ones, but I THINK they interchange.
PS: Hope you received (or should recieve soon) the parts info. I sent. Went out 2 days ago.


dculkin, Point well taken, but since my lines and switch over valve are pristine (tested and checked) I opted for the easiest to get to spot to add the parallel line since I am an inveterate "fiddler" and I throw a vinyl hose on the "gang" often.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Thomas, that is the location I had in mind, although I would defer to the more experienced people on the board. I was looking at my 1985 300D last night to pick a location for the tee connection and was surprised at just how small these pressure lines are. I guess the small diameter doesn't hurt anything because all these lines do is sense pressure, so there is no pressure loss like there would be in a line carrying an actual flow rate. It would be interesting to see whether a gauge connected directly to the manifold would show greater pressure fluctuations than a gauge at the location shown in your photo.

I just ordered an Isspro gauge which I plan to connect at the location shown in your photo. I think I will mount the gauge in the ashtray.

I also think jba's point is well taken.

Jbaj007 - thanks. There's a nice 380SEL at the local wrecker - that might be a good match for my 1983. I'll let you know when the package arrives - thanks again.

Dculkin - thanks for helping me think this through. This location should disclose whether either the line or the switch are jammed (or the turbo is blown!)

Thanks again for the tip - I have added a page to my transmission tuning piece and credited you with the suggestion here.

Very interesting on the economy gauge idea...was the gauge ever put on 123 instrument panels?

Even if the 126 gauge part would fit on a 123 (I'm guessing not), I don't want to lose the mechanical oil pressure gauge...

The gasoline 123s like the 280E and 280CE have the economy gauge and one of the guys out in the Bay Area who put a 4 speed 240D transmission in his 300TD rigged up the 280, 123 econo gauge as described here and it worked fine.

Ben

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www.reproduce100s.com

Thomaspin: your website is not Mozilla friendly - can't see anything but "e-mail" on the index page. Could you please post the url for the page explaining the econogauge?

thanks.