Low oil pressure 6CTA 450

[cam]

Hi,

 

I’ve got a low oil pressure problem on one of my 450s, After a run at cruise and slowing down to idle, alarm will sound, on port engine. I disconected the Cummins panel alarm a few years ago, as it was always alarming, even with 20PSI at idle. I just use a stand alone 10 psi switch, on the back up Aqua alarm panel. Engines have 7,000 hours on them and have been serviced regularly, their whole lives. Anyone have any ideas?

 

Thnaks,

Cam

Topic

[cam]

Thanks Tony.

I was fishing and there is no worse way to end a day, than having the oil pressure alarm ghosting, when you come back to idle! I’ll try bumping up the idle a bit and see if the shifts are still smooth.

Thanks,

Cam

[Tony Athens]

Idle speed–What ever is comfortable.. I would not worry about you OP you are in spec.. Go fishing

1 user thanked author for this post.

cam

[cam]

Hi Tony,

The tachs are Aetena digital and accurate. Is the idle RPM you’re referring to, in gear or neutral? There is around a 50 RPM difference between the 2. Should I set idle in neutral to around 700?

I can confirm the pressure does rise quickly, but I didn’t note it down during the test.

Thanks,

Cam

[Tony Athens]

As Rob said, you are within spec.      A couple of things that you need to understand. Cold oil temp is typically ambient– 70-90F ? After your run, oil temp could easily be 40-75F above coolant temp ( 200+F)  Check you tach for accuracy as the minimum  idle RPM of 600 w/ 650-750 more common.  Once hot , what is you accurate OP at 750-800 RPM?  Bet is comes up quick. Also, these are not high OP engines, they are high volume oil flow engines. The minimum OP spec on the newer QSB 6.7 is  5PSI and 8PSI on a QSC-QSL      

 

 

1 user thanked author for this post.

cam

[Rob Schepis]

Well that’s within spec. 10psi idle. 30-75psi otherwise.

1 user thanked author for this post.

cam

[cam]

Sorry for the slow reply, but I wanted to run the boat, with a mechanical gauge, to answer properly! So here we go; Water temp was 20* and the engines ran at 165*, once up to operating temp. It has been 100 hours/3 months since last oil and filter change. Took her out for an hour run @ cruise and noted the pressures below, finishing up with the RPM/oil pressures after the run

Start up:

650 RPM in neutral oil pressure 72PSI

600 RPM in gear oil pressure 52 PSI

2,250 RPM Cruise for 1 hour 57PSI

670 RPM in neutral oil pressure 14 PSI

630 RPM in gear oil pressure 12 PSI

I believe that is all the relevant info.

Thanks for your help!

Cam

[Nick Mislak]

FWIW mine does the same thing after I switched to the SMX controls if I don’t baby it down from cruise RPM.  It’s annoying as can be, that and the boost gauges have never read right consistently.  It’ll read right then just go out to left field randomly…wiring and ground and everything has been checked, either sensor or software related at this point, seaboard was supposed to send me new senders but never happened and I got tired of following up 

[Rob Schepis]

Have you confirmed the actual psi with a mechanical gauge?

[Author]

Replies