Lately i was having very erratic oil pressure readings, half the time it would work correctly otherwise when i would be cruising at like 65 it would be just under 40 and then if i got into it or was going faster it would drop to the lower safe level and really bounce around, however if I let off it would go right back to under the 40 mark. So I had my local dealer replace the oil pressure sensor but they put in an aftermarket one because the stock one was about a 5 day wait. Now it is very consistent with the oil pressure, however when idling it is lower down by the lower safe level as pictured below and then when i get above 1200 rpms or so it will show normal pressure above 40. Is the lower reading at idle just a difference between the stock and aftermarket sensors or do I have a bad oil pump or something else??

 

415k could be the bearings finally " breaking in" Think of it as you still have a positive pressure of 25-30psi at an idle and 40+ when up in RPMs.. I would watch it with the new wending unit and just look for consistancy.

 

If it had something to do with the bearings wouldn't I notice a difference in pressure throughout the rpm range? It stays low like that til about 12-1300 rpms and then it quickly shoots up to 40 and increases from there with rpm. Is it possible that the aftermarket sender is more accurate reading the oil pressure at idle then the stock was in my truck or is it more logical that something else is wearing out causing the low pressure?

 

Ok so my guage is still acting up very bad and showing erratic readings, for instance, after driving for awhile like half hour to an hour it will show lower pressure at high speeds then low speeds and is very erratic. Is it likely the aftermarket sensor is that bad or do I have another problem like an oil pump?? Any opinions would be great!

 

Put a mechanical gauge on it for a test. Use the 1/8" plug on top of the oil filter housing. Use any cheap pressure gauge for the test. Takes 5 minutes to install, but a lifetime of security knowing what you really have. The factory oil pressure gauge is about as accurate as the light.

 

Ok I will check using a mechanical gauge and let you guys know. The gauge has been very consistent until today when after driving for 45 minutes or so the gauge would drop below 40 and would go lower the faster I would go like 65 and over just like it was doing with the old sensor. What could be causing this only with a hot engine besides a bad sensor?

 

My 94 12 valve with 27k miles reads below 40, but still in the safe zone at idle, like you described. When I get going and the rpm's increase it goes back up to 40+. It has been bugging me a little, so I think I will run a mechanical gauge as well when I get time to check it. The truck is like new, oil changed religiously by the previous owner with DELO. Now it has rotella t in it. I doubt it is anything for me to worry about, but I am curious. My 95 runs 40+ all the time, idleing or not, and it has 206k miles.

Joe

 

Update a local mechanic hooked up a mechanical gauge and drove it for an hour and said the oil pressure is perfect and very steady. Installing a cummins sensor tomorrow will let you know how it works after. Thanks for all the help!

 

Replaced the sender with a cummins one and it works perfect like it used to! Thanks for the help!

 

cummins spec is actually 10 psi at hot idle

 

10 psi is the minimum spec from cummins, mine read 25 psi using a mechanical gauge the reason I was annoyed with the aftermarket sensor is that it was very erratic and inconsistent it would sit at idle and just tick back and forth like 10 psi at times and was not steady at all. Installing the cummins sensor fixed the issue, now it might read higher than it actually is at idle but at least it is consistent and not erratic.