What would I expect to see...

[steved]

OK, I have a question...



With all the issues with failing injectors filling crankcases with fuel and essentially diluting the oil, and I assume making it thin... what would oil pressure do?



And I am talking on a "real" guage, not the faker dodge put in the dash. I currently sit around 56-60psi at hot/cruise... idle around 20-25psi.



I just cranked 100k and even though I check the oil everytime I stop for fuel... I was wondering if the oil pressure guage would give an early warning??



steved

 

[steved]

Hmmm? No one wants to take a shot at this?



steved

 

[LEPage]

No diesel mechanic here, but with nearly 30 years in the Steamfitters, you could say I've been around a gauge or two. I see no way that the gauge would indicate fuel in your oil, as pressure is pressure, if you're measuring oil, air, fuel, water or anything else. Now if the fuel would cause the oil pump to malfunction before something else went south, than I guess it would.

 

[steved]

You wouldn't think the thinning would cause the oil pump's pressure output to change?



steved

 

[LEPage]

Understand where you are going with this, as pressure is higher at cold start, but if you take a good mechanical gauge, test it with 40psi of water pressure, 40psi of motor oil, or 40 psi of air, it will always read 40psi(g).

 

[DavidThompson]

Electric Gauges Are Fair At Best... ... i Will Be Running A Manuel Gauge Or Another Electric To Compair Hot And Cold Psi As Soon As Time Permit Me To Install Either..... back To The Question... . diesel Fuel In Oil Will Make Pressure Drop At Idle Or Full Rpm... By About 5 To 10 Psi... ... i Have Always Took A Cup Of Water And Took The Dip Stick And Let A Drop Of Oil Drop Into The Water..... if The Oil Stays Together... their Should Be No Fuel In Oil... but If The Oil Seperates And Little Rings Of Fuel Run To The Outside Of The Cup Then A Closer Look At The Whole Situation Needs To Be Addressed... ... ... i Always Use Cold Water And Cold Oil... ... trucksalesdave

 

[GColeman]

Depending on the sensitivity of your guage, it seems logical that at some point, you would see some drop in pressure. I would think that more pressure would show pumping thicker oil vs. oil heavily diluted with diesel fuel.



Odds are you might detect some other symptoms before a pressure drop though. I would think rough running or idle, engine knock, etc.



I'll be interested to hear what the experts have to say on this. A stuck injector is always in the back of my mind. Besides upgrading my filtering system, all I have been doing is checking the oil level at each fuel stop.

 

[steved]

Understand where you are going with this, as pressure is higher at cold start, but if you take a good mechanical gauge, test it with 40psi of water pressure, 40psi of motor oil, or 40 psi of air, it will always read 40psi(g).

You are correct that a guage will read the same pressure regardless of the media, but if the media being pressurized reacts differently to the pump, then your guage should read different... pumping air with our oil pump will most likely cause the guage to read read different than when pumping oil...



I never heard of that "test" with the oil drop in water, but it makes sense since there should be less "light" ends in a motor oil.



I'm in the same boat... I would hope there would be some sort of "early warning" with a failed injector, but for now all I have is the oil level and possibly the guage.



steved

 

[lmills]

the pressures you mentioned looked good to me.