Hello,

I have been around here for a while but I believe this is my first post. My '91.5 W250 CTD was my dads and has been in the family since it was bought new in '91. She only has 76k miles and the oil pressure has been fluctuating lately. The oil level is full & clean. I haven't found anything about it in the FSM so far except for R&R info on the oil pump, oil filter bypass valve and the oil pressure regulator valve/spring. With only 76k miles it seems a little premature for the oil pump to be failing especially a gear type. Does anyone have any ideas or experience with this situation?

Thanks, Gene

 

What are you basing this off of? Factory gauge or mechanical gauge hooked up?

Factory gauge can start to get lazy so I wouldn't worry about it.

 

Sticky has loads of great info in it.There is a link to a write up by a guy who has a fix for the wonky gauge.

https://www.dieseltruckresource.com/...d.php?t=167254

 

yesterday morning i changed a fuel filter along the road in the dark(jelled french fry oil!).later that day factory oil pressure gauge started to fluctuate.got fuel in the plug at sending unit. cleaned it up and no problems with gauge.

 

The factory gauge. It will sit at or around the 2nd line then start to drop. The idiot light will light up occasionally. This is something new. It has not done this before.

 

Thanks, I'll start digging

 

Mine was running at almost no oil pressure on the factory gauge for some time...I was paranoid to all heck over that. SO I finally hooked up a temporary mechanical gauge. I was getting 50lbs at idle and 80 lbs over 1500rpm. SO I've since stopped watching that gauge on the dash.

 

Maybe an aftermarket gauge or fix the oem unit is in order. I was hoping the pump was a little young to be going out.

 

That's somewhat worrying. I bumped my OP plugin when I was screwing with my truck one night, took off in it the next morning and watched my OP gauge drop to nothing while I was cruising along at 55mph.

Even though the gauge completely bottomed out, my light never came on...

 

The light doesn't stay on it just flickers and is rare. If that makes any difference.

 

I read the sticky and it describes my issue to a T. I'll go get some dielectric grease and contact cleaner. Hopefully it will fix the problem.

 

could also be a bad sending unit

 

Is ther a test for the unit, ie resistance, etc...?

 

sending units are known to get less sensitive over time.

 

Well I did a resistance test on the sending unit side of the sensor and with a potential range of 30-55 ohms per the FSM the meter read about 53 ohms. It read this about 3 or 4 times but bounced around alot the rest when it would read.

I also cleaned the plug per the sticky, but it was no help. The contacts were as clean as new anyway.