bulltamer

my oil pressure has been dropping during normal driving, i dnt trust the stock gauges so i went and bought a mech. gauge today and were do i plumb it in at?

and another thing my lights pulse with the idle of the motor what would make it do tht?

ofcmarc

You can either Tee into the factory sender's port or use the plug on top of the oil filter housing.

Some claim that the latter is less accurate but that's where I put mine.

wannadiesel

Check the main body ground on the core support in front of the battery.

bulltamer

where is the factory sending unit?

jimbo486

The factory oil pressure switch is in the main oil galley on the driver side of the block. Look directly behind you're power steering reservoir. It's hiding behind it .

bulltamer

thank you kind sir and what should the oil pess. run at idling and at WOT

jimbo486

Cummins specs a minimum allowable of 10psi at idle and 30psi at rated speed (2500RPM).

SORTIE

what is the stock "OIL" guage measuring?

it's certainly NOT pressure (like my M-B wagon's)

I can't understand why a diesel-powered vehicle wouldn't be equipped with an O.P. gauge

someone here has "install a fuel pressure gauge" as part of his signature, what about oil pressure???

ARbowhunter7

You are asking what the factory Oil Pressure gauge measures? That would be the pressure of the oil. Did you think it was an oil temp gauge?

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SORTIE

when running, my '85 diesel Mercedes OP gauge has a range of movement counterclockwise from 4:00 to 12:00, it's at noon when I apply throttle, 4:00 when idling (if memory serves)

the oil pressure gauge in my 1st gen just sits there in the middle of the dial, almost looks like it's measuring the [U]amount[U] of oil present

it just says "OIL" - nothing about pressure

wannadiesel

I think of the Dodge gauge as saying "Yes, you have some oil pressure."

The ol' Benz has a mechanical gauge, the Dodge has a purposely slow electrical gauge. Oddly enough, you can't really tell how much oil pressure you have at road speed with either setup.

I always thought it was funny how the Benz oil pressure gauge pegged on the high side right off idle. It was like the engineers said "If you have 3 bar oil pressure, you have enough. You don't need to know how much you really have."

To the OP: For the pulsing lights, make sure the main body ground right in front of the battery is OK.

ARbowhunter7

Haha. You're serious?

Yes, it says oil. The "pressure" part is supposed to be common sense. Same way that your "Fuel" gauge just says "Fuel", not "Fuel Level". It is common knowledge that the "Fuel" gauge is the level of fuel remaining in the tank, not fuel temperature or fuel pressure.

And before anyone steps in and says, "Hey, there are oil temperature, fuel temp, and fuel pressure gauges", YES, I do realize this, but VERY few stock vehicles come with these gauges.


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SORTIE

the indicator never moves, so how could it be measuring pressure? it's set up just like the fuel gauge, but it doesn't move (even with the ignition off)

ARbowhunter7

That's just because factory gauges are generally crap....especially true in this case. As wannadiesel said, factory gauge accuracy is very poor; bad enough, in fact, that the factory gauge can only be relied upon to determine that you actually HAVE oil pressure.

Heck, mine reads fine, but drops to near zero at WOT. I immediately purchased an AutoMeter Oil Pressure gauge to get a real reading. Turns out my oil pressure shoots up under load (as it should) rather than drops.

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Jklawinsky

^ that had to be scary