oil pressure reading w/key in glow position?
 

When turning key to the glow position, is it normal for my oil pressure indicator to jump to above zero, or is my sender going bad? This is on the 92 300D. Thanks!

is the sensor electrical or mechanical?

I believe that mine goes full-scale when I turn on the key, back to normal when it starts.

I've always been curious about this with regard to the SD. It jumps up to 1.0 in the glow position. It makes me wonder if the running position is accurate.

afaik It should sit on 0 untill running, thats what all of mine do...

All of the w124 mercedes Ive driven do that so its most likely normal.

My 124 car's oil pressure electric gauge stays at zero until the pressure builds up. It's actually faster responding than my 123 car since the latter has a mechanical gauge and the pressure has to travel up the little tube to the dash.

When my 124 had a bad oil pressure gauge sender (mounted on the oil filter block) it would read above zero with the car turned on but not running. My first guess, therefore, would be bad sender. A new sender cured my problem. It took my mechanic two senders over 6 months to get me a good one, BTW.

Jeremy

My dad's 300SDL goes up to 3 on ACC and goes to 0-3 bar when started...

Please explain what "goes to 0-3 bar when started" means. Do you mean that it ends up somewhere between 0 and 3 bar? or that (after being at 3 bar in position 1 – ACC) it drops to 0 and then goes up to 3 bar? or something else? I want to make sure I understand you, I've never had a W126 car.

Jeremy

IIRC mine stays at 0 until the oil pressure comes up...

-Jason

OP reading at "Glow"
 

Nope,
'Just went out and turned key to "Glow"...OP Gauge unresponsive.
Engine Start- OP gauge pegs.

Yours might be sensor (As suggested) [Or Wiring problems]

My personal guess on this one is that the OP gauge loses power when the starter circuit is engaged and shuts off all the accessories to provide every last bit of available current to the starter. The sensor's grounded out, it pegs to 3 any time the gauge has power, they hit the starter and it drops to zero, and then as soon as the voltage comes back it pegs again.

IF their gauge EVER reads anything while the engine is running (like a warm idle) besides a pegged 3, then I'm wrong.

Mine, for the record, stays fully at zero until the engine is running and has pressure.

EDIT: I just realized why this doesn't exactly make sense. The electrical OP gauges do not lose power under starting, because I just remembered that I can watch my starter bring the oil pressure up from zero before the engine ever starts firing on its own. So, I'm changing my guess to "wiring problem" :D Sorry

I'm still going with normal, a gauge check just like the lights coming on. Mine both did the same, full-scale when first turned on, then reading normally in start and after starting.

ok, I'm curious to what it reads right after you turn it off then?

"It depends"
 

1. 617 engine w/mechanical gauge – sinks to zero over a couple of seconds after engine is shut off.

2a. 603 engine w/electric gauge – goes immediately to zero when key is turned OFF.

2b. 603 engine w/electric gauge – sinks to zero over a couple of seconds after engine is shut off with STOP lever (key left ON).

Jeremy