300sd 1983 260K daily driver 200 or so miles a week
Friday afternoon noticed a fluctuating oil pressure needle
thought it was a bad ground, cleaned the plug on the sender
all seemed ok drove home. low to no pressure at hot idle looked at and
improved the connection at the sender (resoldered the wire to sleeve)
as it was a bit frayed, still low to no pressure at hot idle.
replaced the orings on the oilfilter canister shaft. still no difference
gauge pegs at three bars at anything above 1200 rpm.
The weird thing is that this all happened suddenly not like a slow progression towards being worn out.
willing to change out the oil (mobile 15/40w) on the chance that might make a difference
the last oil change was in September and there's little to no oil consumption.

what am i missing?

Possible worn out oil pressure sender?

Can a mechanical sender be installed to verify pressure ?

Possibly, the needle seems very quick on the uptake movement.

a mechanical sender was the next step

X2..........has yours ever been changed? Aftermarket one from Pelican $56, OEM from Pelican $100.

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'89 260e (212K Mi.), '92 400e (208K Mi.), '92 400e (not a misprint) (146K Mi.), '95 C220, '81 240D--Sold

Perhaps the thing that screws into the backside of your oil pump... which determines the pressure by different springs.... three different designs at least over the years.. has come loose... or fallen out.... or has broken...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I bet the sender is worn out. The live gauge in my 84 190D is always on point. Nice and smooth, accurate, immediate reading. The electric one in my 85 190D is twitchy, not perfectly accurate, and I hate how it doesn't sit at 0 perfectly like the live one does when KOEoff.

Throw a new sensor on it and see what happens. If you had no oil pressure for real, you'd hear it and the engine wouldn't last long at all.

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
http://badges.fuelly.com/images/sig-us/302601.png
http://i959.photobucket.com/albums/a...0/sideview.png

how old are the o-rings on the canister spindle?

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

fresh as of this morning

Iam betting the Electric Oil Sender is bad. Got any PNP type yards in the area? Pull one off another car.
Do you have a spare Oil Filter Lid? Drill a hole in the top, thread it for a mechanical Oil Gauge to see where you are at. Drill between the webs in the casting under the lid.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

This isn't exactly a fool proof test but it might give you an idea of oil pump health =>

(get some rags to mop up first)

At idle with a low pressure showing on the gauge open the oil filler cap and see if you can see any oil being sprayed inside. A healthy oil pump should be pushing quite a lot of oil through to the top of the engine - with a decent bit of diesel blow-by you should be able to water proof your neighbour's fence!

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Picked up a VDO sender today, see if that solves the problem.

I am amazed that so many people have confidence or experience with an electrical sender exhibiting partial failure...
On the other hand ... the item on the back of the oil pump... which will allow pressure over a certain amount to be vented from the system back to the oil pan... if blown... could display this behavior ... the amount escaping at low rpm's actually depriving the system of proper oil pressure.... but at higher rpms being supplied due to the restrictive nature of the size of the escape hole.

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Certainly it might be the oil pressure relief valve. An old sender is just a better possibility.

Even at low idle with no oil pressure at all the engine should be noticeably noisier as well. Since he has not mentioned this. There are still reasonable grounds to think it might be a tired sensor.

I usually prove a part is bad out of habit before buying another one. An old habit perhaps from working many years in the electronics field.

Swapped out the sender and it resolved the issue, will open the old sender to see if the 32 year old innards have an obvious flaw, photos if its clear. thanks for the ideas.

Great forum!!!