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Wayne
Wayne, Journeyman
Category: Heavy Equipment
Satisfied Customers: 5465
Experience:  34 years experiance as engine rebuild and problems.Thermo-King repair and trouble shooting.
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low oil pressure in my N14 cummins

Customer Question

I have low oil pressure in my N14 cummins when it gets warmed to 185 degress. Startes at 45 PSI cold then drops to 8 PSI @185 degress @ 600 RPMs, how can this drop that much just warming up? I have a new oil cooler, new oil pump, new turbo, new piston oilers, new rod and main bearings, and new oil and filter. Also have been told from inspection my cam bearings are good, with no excessive leakage showing from pressurizing oil system with pan off.
Submitted: 2 years ago.
Category: Heavy Equipment
Expert:  Bobby Long replied 2 years ago.
N14 Cummins Quick Sheet

The N14 Cummins was definetly one of Cummins most popular engines. Used to power everything from over the road trucks to motorhomes to mining equipment to generators, the Cummins N14 was very versatile.

The Cummins N14 was built on the basic design of the 855 cubic inch Cummins engine. In the early 1990's, Cummins redesigned the engine with electronic controls to meet EPA regulations. The redesigned engine, known as the Celect fuel system, featured an Electronic Control Module (ECM) and electronic injectors. Although injectors were still cam activated, the Cummins ECM controlled fuel at the electronic injectors.

In 1997, Cummins released the upgraded N14 with the Celect Plus fuel system. Although not noticably different looking, the Celect Plus ECM has many more adjustable parameters for customer fine tuning.

The Cummins N14 was discontinued around 2000, and has been replaced by the Cummins ISX.

Use the charts below for useful information for the N14:Engine Ratings

Advertised hpPeak Torque lb-ft @ rpmGoverned Speed
310 - 5251250 - 1850 @ 12002100

Maintenance Schedule(Why Fleetguard Filters?)
Oil Filter12,000 Miles
Fuel Filter12,000 Miles
Coolant Filter12,000 Miles
Valve Adjustment120,000 Miles, 3000 Hours, 2 Years


Filter Part Numbers (Fleetguard Numbers)
Oil FilterLF3000
Fuel FilterFS1000
Coolant FilterWF2071


Useful Specs
Intake Valve Clearance.014"
Exhaust Valve Clearance.027"
Engine Brake Clearance.023"
Firing Order1-5-3-6-2-4
Oil Pressure10psi (Idle), 25psi (1200 RPM)
Fuel Pressure25psi (Cranking), 120psi (1200 RPM)
Customer: replied 2 years ago.
Thank you Bobby for responding, I do have a service repair manual with all of this info but my concern with low oil pressure is, do I have an internal leak that is reducing my pressure shortly after oil leaves the pump ? Are there an seals or gaskets that can leak under the front cover in the oil gally ? It seems that my whole system is consistently low as soon as I start checking after the pump. Do you have any ideas ? Thanks,
Expert:  Bobby Long replied 2 years ago.

Hello again.

I would say that if you pressurized the oil system with the pan off and didn't see any extra leakage then I would start with the new oil pump that was installed could be failing or not shimmed up correctly. or maybe the oil pressure relief valve spring is weak or not sealing completely. Its possible that the new oil pump has failed. Sometimes new parts are always good. Hope this helps

Bobby Long, Technician
Category: Heavy Equipment
Satisfied Customers: 380
Experience: 16 Years experience in Bobcat, And International tractor repair
Bobby Long and other Heavy Equipment Specialists are ready to help you
Customer: replied 2 years ago.
Update, I checked the regulator spring and plunger in the oil pump and is working correctly. My next concern is if the head gaskets could have a leak that would allow a 10 lb. or more drop in oil pressure, this is my best estimate off the loss that I see. I did a check on the oil ports to the jake brakes on top of each head and all are consistant pressure with each other.
Expert:  Bobby Long replied 2 years ago.

Hello again..

Well I have never seen it happen on this engine but I suppose anything is possible. Im kinda running out of ideas.

I have seen main bearing marked wrong they would say there std size but would really be .010 undersized. This happened to me on a 466 international. It was not making any noise but was loosing oil pressure big time. We ended up rolling the main bearings back out and measuring them and found out the one was undersized.

Customer: replied 2 years ago.
Thanks Bobby, they did plastic gage when they installed new bearings so I feel pretty confident about them, I guess I'm wondering since my oil pressure is so low at the start of the oil rifles and my pump is in the allowable range could I have a leak that big in the front plate of the engine where the oil gally comes across from pump to the right side ?
Expert:  Bobby Long replied 2 years ago.

Well if they plastic gaged the new bearing then I'm sure that not the problem.. Let me call around tomorrow to a few friends of mine and ask then if they seen this before. I'm just running out of ideas... Sorry. But I will let you know something tomorrow about what they think or if they can give me any other ideas...

Customer: replied 2 years ago.
Than you Bobby, I am running out of things to check too, I appreciate your efforts and will wait to see what you can find out.
Thanks again, Dave
Expert:  Bobby Long replied 2 years ago.

Hello Dave.

I called a friend of mine and he said he has seen the gear on the oil pump shaft start slipping. And also the pistons coolers brake off would cause this .

Customer: replied 2 years ago.
Thanks Bobby, I did install all new piston oilers yesterday, althought I couldn't see anything wrong with the old ones. Then started it up to check oil pressure, it was still the same, no change. As far as maintaning pressure at the pump, it will hold over 100 PSI at 2100 RPMs @ 185 degrees as long as I want to keep it running. The pressure at the pump doesn't waver at all, but seems to drop off as soon as it hits the oil rifles. This is why I'm looking for a leak in the oil galley, I don't know what else could be wrong unless cam bearings didn't show enough leakage when they pressurized the system. I appreciate anymore ideas you may have.
Dave
Expert:  Bobby Long replied 2 years ago.

Hello Dave,.

I will do some more checking tomorrow and let you know if I come up with anything else..

Customer: replied 2 years ago.
Thanks Bobby, I will wait for your message, much appreciated, Dave
Expert:  Bobby Long replied 2 years ago.

Hello Dave.

I checked with some mechanic friends of mine today and they couldn't come up with any new ideas. I'm going to email our conversation to the other heavy experts on here to see if they can help..

Customer: replied 2 years ago.
Thank you, XXXXX XXXXX your help. Dave
Expert:  Wayne replied 2 years ago.
Hi I'm Wayne,
I will Try help you with this,
as a engine rebuilder , 2 places you will loose oil pressure ,baring a good seal and oil pump,

is Main's, and the most over looked, seen it 100 times , Cam Bearings
shops, people do over hauls, In chassis and they do not replace cam bearings, not the heart of the engine , but liver, must pass thru this, and continue with a good oil pressure
Customer: replied 2 years ago.
Hi Wayne, do you think pressurizing an engine with oil, and with the oil pan off can show excessive leakage on cam bearings ? We did this and felt that there wasn't enough leakage to warrant replacing them. Is this a good test ?
Thanks, Dave
Expert:  Wayne replied 2 years ago.

Morning Dave ,

In my opinion no, reason bearing, the cam is not moving , so may be sealing off the low spots.
As rule of thumb, I have always cam bearings, so not to have a problem when rebuild is done.

Wayne
Customer: replied 2 years ago.
Thanks Wayne, this problem has been a mistery from the beginning, but I am starting to agree with you that there must be some wear in my cam bearing. We have pretty much replaced everything else and pressure checked and temp checked water and oil and nothing stands out, so looks like another project ahead soon to replace cam bearings. Thanks again, Dave L (Customer)
Expert:  Wayne replied 2 years ago.

Morning,

You are welcome,
as I said early on , don't take chances when you are doing that much work and already into it .
Have a great day Cool


If this helped you, please hit accept...if not get back to me
Wayne, Journeyman
Category: Heavy Equipment
Satisfied Customers: 5465
Experience: 34 years experiance as engine rebuild and problems.Thermo-King repair and trouble shooting.
Wayne and other Heavy Equipment Specialists are ready to help you

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