I have fixed my tach on my 83 300SD, and I now want to get the oil gauge to work (it does intermittenly).

How can I diagnose the problem? I was thinking of starting with replacing the sending unit. Where is this?

Also, is there another way to check the oil pressure to know that there isn't anything wrong with the pump? I think the pressure is good as I have taken it on several long drives and the engine shows no problems, (plus the previous owner said it quit years ago and she had it checked out).

Thanks,
Chris

First determine if your oil pressure guage is electrical or mechanical.. on our 123's often it is mechanical... with the tube going to the guage on the dashboard.... if it leaks your pants legs look really bad....
I assume yours is electrical from what you say...
If you can borrow another one to hook to the sender that would check the sender...
The sender is probably bolted into your block... you might consider taking it out and cleaning it first... a little carb cleaner sprayed on it... and dryed off might help if stuff is clogging the access hole to the electrical sensing part...
Do you have a Haynes manual for your car ?

I don't have the manual yet. Is the sender under the oil filter cannister?

I do not have a manual for your car....
someone will get back from the Holiday and know exactly where it is...

If it's mechanical the line comes right out of the filter housing and goes through the firewall. Should be a small line from the bottom outside of the housing if it's there. Sounds like it may be an electric guage like Greg said unfortunately.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

The oil pressure sender is electrical on your car and comes off the back of the oil filter housing. It's a one wire hook up that often lacks a great connection; loose or oily. Check the wire first.

Picture of it on FastLane (above), type in for 1983 300SD Mercedes.

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The Golden Rule

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

I checked the wire and connector, and they are clean and tight. How can i remove the sender for cleaning? should I drain the oil from the filter housing first?