Bought this car, 1981 300sd, about two and half weeks ago and the tach has always been a little weird (cigarette butt thing, I know, just haven't messed with it yet), the fuel and temp gauges seem to fluctuate a little bit based on how fast or hard I'm press the gas (rpm's I suppose). For instance, yesterday, I turn the key to wait for the glow and look at the fuel, it's just below a 1/4 of a tank, I say to myself, I better get some gas. I drive it for about 30 minutes, it's moved up to just below half a tank now

I just fixed the 3/2 way vacuum regulator on the top of the engine and I'm wonder if that might have anything to do with the oil pressure gauge being dead? The night after I fixed the 3/2 way, the oil pressure gauge was dead, then, then, about ten minutes into my drive, I look at the dash, it's up over 3 bars, and hovering around 2 bars at idle.

Yesterday, it never moved. I checked the oil, it was fine. Starts, drives, stops fine. Is there a sending unit or some part/piece/wire that I can check to see if it's broken?

Thanks.

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1994 C280 204k miles

There is a sending unit at the bottom of the oil filter housing. Sounds like there is a grounding problem if it works intermittently.

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2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
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'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold

One of the searches I pulled up a guy said he opened the oil filler cap to see if the engine was getting "bathed" properly to make sure it wasn't the pump, guess I can do that, too.

Thanks for the tip on the location of the sending unit.

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1994 C280 204k miles