fluctuating oil pressure ???

[Don in Missouri]

Greetings from Las Vegas.



During the last hours of our drive from Missouri I noticed the oil pressure gage behaving strangely. I have good oil pressure at idle and when lugging the engine. If I wind it up, the oil pressure drops.



I drove the last 100 miles at 65 mph. If I exceeded that, the oil pressure would go down. It would hold a little more pressure while climbing hills, and a little less while coasting down.



Any ideas what I am facing?

 

[1stgen4evr]

Oil pressure

My thought is to install a direct reading gage so that you know what the pressure really is. The factory system is signal type with known problems. Voltage fluctuation associated with higher speed could very well be the source of your fluctuation in oil pressure. BUT, if you actually have fluctuation, the answer to what you face is serious. There have been post on problems with the thrust washers on the crank. Higher rpms could be exhibiting a change in oil pressure if that were the case. A loose pickup tube (although I have never seen this in a Cummins) will exhibit fluctuations.



Good Luck

James

 

[bgilbert]

Any ideas what I am facing?

Nothing unless you have a true oil pressure gauge, and are reading numbers and not marks.

 

[nascar mark]

Greetings from Las Vegas.



During the last hours of our drive from Missouri I noticed the oil pressure gage behaving strangely. I have good oil pressure at idle and when lugging the engine. If I wind it up, the oil pressure drops.



I drove the last 100 miles at 65 mph. If I exceeded that, the oil pressure would go down. It would hold a little more pressure while climbing hills, and a little less while coasting down.



Any ideas what I am facing?

Stupid question, but have you checked the oil level?

 

[Greenleaf]

The electric OEM gauge is not reliable. You'll want to monitor it with a mechanical pressure gauge temporarily set in the cab while you drive. When you find that all is ok, then replace the sending unit with new and you'll be a happy motorist once again.



-S

 

[Don in Missouri]

I did verify the oil leve was safe, and added a little just to see if it would make any difference. It did not.



I'm gonna try a new sending unit before we drive home. The oil warning light is working and does not come on when the needle on the gage drops.

 

[Don in Missouri]

The new sending unit did the trick. Oil pressure was fine for the 1600 mile journey home.



Photos are posted at http://imageevent.com/shaggy/yuccamttrip

 

[bgilbert]

Yep I knew that crew cab looked familar. Don I saw you west bound somewhere along I-70 either in Colorado, Kansas or maybe Missouri on my trip to Sams house in Colorado, I was driving my 91 W250, you were looking too Remember?

 

[Gary - K7GLD]

I hate to tell ya, but there was probably NOTHING wrong with the original sender...



What probably WAS wrong, was a poor connection at the plug at the oil pressure sensor that only needed a good cleaning - sometimes merely unplugging and then re-connecting does the job, and of course, that's what happens when you install the new sender, and when it then works, you assume it WAS a bad sender when it really wasn't...



Had the same problem on my '91 - a good cleaning usually took care of it for a year or so, then erraticc PSI again... Still had the original sender when I sold the truck after buying the '02...

 

[Greenleaf]

I installed a fresh sender last spring. It sat all winter and as soon as I got back out onto the open highway it flucuated.



Guess what... ..... same thing again this spring. I unplugged and re-plugged several times and it's working again.



I have a mechanical oil psi gauge installed in the cab, so it really dosn't matter any longer.



GL

 

[Don in Missouri]

Yep I knew that crew cab looked familar. Don I saw you west bound somewhere along I-70 either in Colorado, Kansas or maybe Missouri on my trip to Sams house in Colorado, I was driving my 91 W250, you were looking too Remember?

I'm sure I saw you, I always watch the first gens, but I didn't know who I was looking at. You must have seen me coming back from one of the two snowboaridning trips I took to Colorado in February.



This last trip all the way to Las Vegas was a third trip. I stopped at Sam's house this time where I got a good look at your old 250 sitting in his driveway.



As for the sending unit vs connection: The sending unit broke in half when I put the socket on it. I'm not sure if I twisted it wrong or if it was just wanting to fall apart. Either way, I was just glad everything was OK.

 

[bgilbert]

Don, looks like you need to install the power ram/cummins emblems onto your crew cab. That would IMO make it look a whole lot better. Did that diesel parts truck come with engine, trans and t-case? Are you going to the St Louis dyno day this Sat the 19th? Info is in the Central events forum.

 

[Don in Missouri]

Yeah, I've been waiting to either find a pair of 350 Power Ram emblems or I'm considering buying some of the new Power Wagon emblems with a new style Cummins C.



The parts truck came complete with engine,T-case and blown auto transmission. I found out last night it also has a PowerLock differential.



I didn't know about the dyno day, but I am going to St. Louis Saturday. Maybe I'll check it out?

 

[bgilbert]

Oh I didn't know you had a 350, I just saw that you have a SRW and seen the emblems from that parts truck. You already have a Cummins in your crew yes? Yep dyno day info in the Central events forum. Sounds like a ton of trucks will be attending. I won't be there til around 3-4pm CST.

 

[Don in Missouri]

It's an '84 W350 with '92 W250 Diesel drivetrain. Jack Holt built it in Austin. I'm just finishing up where he left off.

 

[RWWinslow]

The oil pressure sending unit is a Dodge special - - i. e. not a Cummins design. Dodge parts managers have told me that this is the most common part they sell for the Cummins engines . . . . the diesel engine vibration probably has a lot to do with the degraded performance. My first sender last 325,000 miles. . . .