Cummins 6BTA low oil pressure

[Trianon]

Hello,


I have a Cummins 6BTA from 1992 210hp on a trawler, and recently I experience a curious behavior on the oil Gauge.

Nothing was done on the engine before the change (same oil, water, filters...)

It used to be in the past around 4 bar ~55 psi at 1800 rpm, a little more when cold, and around 35 psi at idle. It has been running like that for years.

And now ( last time I used the boat, during 5/6 hours) , I noticed that the gauge decreased to 2 bar, 25 psi when cold, and after when hot it's even lower I would say 1.5 bar. So I kept the boat around idle. The needle of the gauge is still moving from zero to non-zero but this is a little worrying me. Even if I accelerate to 2000 rpm it does not increase and keeps around 25 psi.


I changed the oil & filter to new ones (they were probably a little more than 100 h) but nothing changed. I also looked at the coolant and it does not seem to have any oil in there. There is no consumption of oil by the motor either.

Any idea? Should I start by changing the "oil relief valve pressure"? For this should I remove the whole oil cooler, plate and so on? I don't have any tool to check the real oil pressure and I dont' see why my gauge suddenly would be divided by 2. Also the oil pressure alarm did not wake up.

Thanks for your help.

[GordMay]

Greetings and welcome aboard the CF, Trianon.

[sailah]

Personally I'd buy a cheap pressure gauge ($10-20) up to 100 PSI and remove the remote sending unit. I don't know the specifics on your engine but there is a NPT fitting somewhere that the sensor is reading. Thread the gauge directly into the block and see what you are reading directly.

Depending on what I saw, I'd start tackling the problem from there.

[Diesel Bill]

The oiling system on the Cummins BT is rock solid. Not saying something can't break or go wrong. That said I tend to agree with sailah and recommend you start with a mechanical gauge to double check the original gauge. Don't tear into the engine till you know what's going on. One other thing that comes to mind is in the past I read FRAM oil filters used a cardboard piece in them that would come apart and pieces would work their way through the oil galleries and cause blockages. Also possible the oil pressure relief valve is stuck in an open position.

[Trianon]

Hi,


I did not use FRAM filter but Fleetguard LF3894. Given your words, I ordered a pressure oil kit and I keep you posted as soon as I get it.

Regards

[Lepke]

Most alarm switches I have seen go off at about 10 psi.

[Trianon]

Shame on me, was just the oil gauge that was partially unplugged from the dashboard. Now it came back to its original level.

[a64pilot]

Originally Posted by Trianon

Shame on me, was just the oil gauge that was partially unplugged from the dashboard. Now it came back to its original level.

Always verify the instrument first.
I had a customer that spent thousands and worried himself to death about high oil temp on a Pratt&Whitney -34 engine.
I showed up and replaced the temp gauge. Boy did he feel foolish, and thankful.
That Cummings you have as long as you don't excessively abuse it is about as rock solid of an engine as their is.

[Trianon]

Hi,


Thanks for the reply.
Regarding the engine itself, I have a turbo without cooling version, it's directly plugged on the intake manifold.
Is there any optimal RPM to run, and what is the oil change frequency?



On the see (salted water), I am used to run around 1800-2000 rpm, but on rivers, I am ususally close to idle, so maybe this also impacts the oil change.


Rgds

[BerettaRacer]

At 1800-2000 RPM that engine is almost bulletproof.

Here is a link to the prime Cummins forum run by Tony Athens, a Cummins guru. Cruise around the forum and the SBmar website and there will be more info than you can imagine.

https://www.sbmar.com/community/

That being said, there is one weak link on that engine needs to be serviced, an easy fix but it must be done, it's nick named "killer dowel pin". Plenty of information online, and it's a cheap and easy fix.
Tony also recommends upgrading the water pump">raw water pump, but not as important as the dowel pin.

Personally I had a pair of those engines as gen sets, and had 14,000 hrs each and still running fine when sold the boat. I did 250 hour oil changes, and injectors at 1200-1500 hours as time allowed, still ran fine but left slight sheen at exhaust output.

[NoTies]

Glad to hear it was a simple fix. Every time I have had low pressure issues with a 6BTA (I'm a marine mechanic) it has been turbo sealing rings gone bleeding off excess oil. An easy and cheap fix unless the housing is stuffed.