Hello All,

Question on a 1992 300D here. Recently replaced motor after a bent rod at 420K miles. New engine runs great...but no reading from oil pressure gauge.

I was getting ready to swap out the oil pressure sensor next oil change, when I noticed something interesting: if I engage the ABS by extreme braking, the oil pressure gauge pegs to top and reverts to 0 when the ABS is disengaged.

I have read in other posts that gauge @ "0" = no power; gauge pegging @ top = no ground. Any ideas on where to begin running down the fault?

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Josh
Ace Taxi
Bangor, ME

Cab 2: '87 300D
Cab 3: '92 300D
Cab 4: '90 300E 4Matic Wagon
Cab 6: '96 E300D
Cab 7: '87 300TD
Cab 8: '91 300E 4Matic Wagon
Cab 9: '98 E320 4Matic Wagon
Cab 10: '98 E300D
Cab 11: '98 E320 4Matic Wagon

'96 Suburban 6.5 Turbodiesel

I've looked at the wiring schematics for both the ABS and the OP gauge...
and other than the Chassis (as ground for both) and the Battery(as 12 volt +
source) there's no meeting of the circuits.

However, (Old Timey) "Bad Grounds" will try to find "Earth" any way they can.

I'll almost be willing to bet there's something wrong with the OP circuit's ground
and It's using the Brake Pedal being depressed to find "Earth".
The Op sender uses the Engine Block as ground...
Hows your Engine to Chassis Grounding Strap?
'Reason I ask this is BECAUSE the actual ABS Hydraulic unit (Behind the Driver's
Headlamp) has it's very own grounding strap to the chassis.

There is a tiny tiny wire off the OP Gauge that feeds to the Indicators (I Lights)
Mayhaps it's participating in this Un Authorized grounding??

Check the main instrument ground behind the Instrument Cluster.

If there's no path from the OP Gauge to the Sender (Or if the Sender's OTL)
[Out To Lunch] the gauge might try another path?

Attached Thumbnails

   

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'84 300SD sold
124.128