View Full Version : Oil pressure issue

16-04-2016, 10:26 PM
Hi all looking for advice on a system I've recently been called to!!

Original call out around 1 month ago to a d6 rj 4000 6 cylinder compressor....

Customer complaining of 1 cylinder head very warm and smoking!

On arrival compressor was isolated by them, I ran system up to find the smoking was from the unloader gasket so ordered gasket and plate set as this was worn commission system running all ok...
Yesterday I was recalled by customer complaining of compressor failing on oil switch..

On arrival I checked the obvious,oil level pressure etc I found was all good until the 2 unloaders were activated under load (eliwell step controller) and my oil pressure suddenly dropped and equalised to suction pressure causing it to activate oil switch I just wondered if any1 has had any problems like this....

It's a dual compressor kit serving 1 evaporator and it's a belt chiller chilling cakes

Set point 0
Ambient 7
Suc temp 6
Discharge temp 85
Liquid 35
Oil pressure 81 psi (when on no load)
Suc pressure 52psi
Liquid pressure 215psi

Cheers guys


17-04-2016, 03:27 AM

Danny read page 7, as it might mean something as to work you might have done.
Does it have crankcase heater?
Is it working, should be warm to touch.
Doeas oil in sight glass foam up?

17-04-2016, 07:57 AM
thanks for ur response

Yes it has crank case heater
Doesn't foam when running



17-04-2016, 10:38 AM
Hi Marsay.
Welcome to the Forum.
Your having repaired the unloader may be a red Herring!
Meaning that now you have re-introduced proper control of the suction gas flow through the Heads being loaded / unloaded.
May have tipped the pressure balance across the Oil diff? Try trimming the oil diff Slightly ( if possible.)

I suspect that you may even have to do a Top End and sump Inspection.
Because what damage caused by the original un-loader fault is at present unknown.

Any recip is susceptible to oil pressure / temp issues. Unless these have been overhauled within an acceptable period. (You know your maintenance schedules I assume?)
I would recommend a service.
Internal Wear / Damage can create some really stage Oil Pressure issues.
I had a Recip once that ran fine during the initial loading but failed dramatically on oil pressure dif, when further loaded.

Someone had added Oil stained water thinking it was a drum of Oil.
Resulting in so much main bearing wear that the Oil System lost its back pressure through the Internal Galleries. Causing Oil Dif Failure.

Just the Ramblings of an Old Engineer but May Help You?
Good Luck Grizzly.

17-04-2016, 11:31 AM
Hi grizzly

Thank you for ur response!!

This is a new customer therefore the maintenance is unknown what did consern me is the onsite engineer has said they have had problems with the tev in the past which could of resulted in liquid back or starving the system?

I myself have being in the fridge game 11 years but only recently started working on stripping compressors the company I previously worked for had the habit of just sending a re manufactured compressor over night and of course meant I didn't get to see what had happened so this is sort of new stuff to me (which I am very keen to progress)

I'm thinking that maybe this compressor has had history and it's now that we're having to investigate the 2nd compressor certainly looks a lot newer than this one I will be returning to site either tomorrow or Tuesday to valve off and strip down I'm wondering if maybe I have a sticky unloader on this head therefore will be taking some spares with me

Ur knowledge is really appreciated



17-04-2016, 06:23 PM
Let us all know how you get on Danny.
You could simulate the Solenoid / Unloading Gears action I would assume. By using a Solenoid coil magnet.
Take the solenoid coil off and stick a large Steel bolt through it. Then when the solenoid energises you wont burn the coil out.
I am probably teaching you to suck eggs? But some nay not of been shown this!
Alternatively disconnect the coil and use your Magnet when you wish to test an unloader.
I think you could well be onto something with the Liquid flood back, Ranger was there from the offset!

Its an interesting issue all the same, plenty to interest us all if you keep us informed.
Good Luck

19-04-2016, 04:50 PM
Hi guys just an update on today's findings

Returned to site and stripped each head individually and two heads had problems pics to follow

Ran unit back up with a good crank pressure 35psi above suction ran good 4 hours on full and part load with no issues fingers crossed that's the end of that

Cheers guys!!!


19-04-2016, 05:39 PM
Feels good to actually Diagnose repair and reinstate, does it not?

Well done Danny, welcome to the world of Industrial, Something got a "Little Hot." Me thinks!

19-04-2016, 06:15 PM
It sure does thanks again for all ur inputs