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Old 01-15-2001, 10:10 PM
jc300e's Avatar
Registered User
Join Date: May 2000
Location: Location: Norcross, GA
Posts: 124
I recently replaced my oil psi sending unit on my '92 400E. Seemed to work great. Now, I have a strange problem.

When I turn the key to "on" position, the guage immediately jumps to "3". When the car is a running temp and I am at idle or slowing down to idle, the guage measures oil psi properly. As soon as I come to a complete stop with brake applied, the guage jumps to "3". Upon release of brake and slight excelleration, the guage drops sightly and begins to read psi.

If I am at idle and the car is in "P", the guage works fine.

Is there a voltage problem or short somewhere?

I installed an OEM sending unit (FYI)...wiring at the unit was quite simple. I can't imagine that I screwed that up.

Comments and advice is appreciated
'87 300E
'92 400E
'06 ML350
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Old 01-16-2001, 08:04 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Loose connector or slight break in wiring. Open circuit will cause the gauge to read 3bar.
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Old 01-16-2001, 06:11 PM
MBenzNL's Avatar
Join Date: Jan 2001
Location: the Netherlands
Posts: 1,417
Can be the oil psi sending unit as well..
I have replaced the sender on my 190D by a new MB sender once. After about 3 months and a trip of 100km flat out my gauge went down to 0 while I stood in front of a traffic light (can you imagine the look on my face...).
I turned down the window to hear the engine, but it still sounded like the oil pressure was good.

It took me a new oil-pump and oil-filter housing before I found out that the sending unit was BAD. Normally when the sender is broken or the cable is disconnected (partly or total) the gauge will go directly to 3 when the ignition key is turned on.

1990 300SL-24
1993 C250D
with a minor 600+k kilometer
(the Netherlands)
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Old 01-18-2001, 08:24 PM
jc300e's Avatar
Registered User
Join Date: May 2000
Location: Location: Norcross, GA
Posts: 124
It jumps to 3 upon ignition "on" position. Then, when the engine cranks, it drops toward 0 and immediately returns to 3 with oil psi.

It's quite interesting to watch the guage at operating temp at a stop light. With Brake applied, it quivers at 3. As soon as I release the brake and begin a slow accel, the gauge drops to 1 and begins it accent to 3 with psi...

I am gonna re-check my wiring connection at the sending unit this weekend.

Can anyone give me a tip as to where the wire terminates on the other side?

'87 300E
'92 400E
'06 ML350
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