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Low oil presure on rebuilt c90-8

S

sibbeston

Registered User
Whitehorse, Yukon
I just installed an overhauled c90 and only getting 5psi oil presure. The gauge was fine on the last flight a few days before. I primed the pump and am getting oil to the valves. I pulled the oil sump off and suction tube looks fine. I even put a jar of oil under the suction tube and turned the engine over as fast as I could for a minute and it pumped about a cup of oil up. The next step is to pull the accessory case and look at the pump. Also going to try a new gauge.
Is it possible the pump is only making 5 psi?
 
5 psi at idle? when you say overhauled, what was done to the case?? Correct brgs put in for the crank? Rods facing the direction they were taken out? Oil pressure relief on its seat, spring in there? Number of things. You said the pump made good oil pressure before so if you did nothing to it it should make pressure now?
 
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I pulled an a65 from the plane and gauge was working a few days ago. I bled the line and checked for obstructions.
The c90 is experimental and I can't vouch that it was assembled correctly. The guy I got it from sounded knowledgable.
On first start up it had zero presure. I added oil to temp bulb and tried again. Still zero. I pumped oil into the front left oil galley plug and finally got oil. 5 psi. I pulled off a valve cover and it had oil.
I checked the spring on the relief valve and it looks ok. I'm aware that proper size bearings affect presure but looking for easy fixes before I open things up.
My next step is to remove the assesory case and inspect the pump. I wonder if the pump is even capable of such a low presure? With the plugs pulled I turned the prop by hand fast and it sucked up a cup in a minute. I have my a65 sitting on the floor and if the pump gears are compatible I can try those. I'll check the part numbers.
Any other ideas are welcome before I start pulling the engine apart.
 
At a barely turning over idle the pressure on a C-90 is nothing to write home to Mother about. One other thing to check is the oil pressure relief valve, spring and seat. If any little bit of whatever gets in there after an overhaul it will show low pressure.

You can also do some reading here to buttress your list of things to check:

http://www.bowersflybaby.com/tech/fenton.htm

Here is the bit ref the oil pressure after overhaul and rebuild:

http://www.bowersflybaby.com/tech/fenton.htm#Low_Oil_Pressure_-_Fresh_Overhaul

I once had a wee, wee little piece of carbon get in the relief valve shortly after taking off from an airport up in the middle of the woods. About ten minutes out over the endless forest the oil pressure took a big dive, garnering my full attention. I throttled back, turned back and started gently climbing in case I had to do a bit of gliding. My eyes were rivited on the temp gauge. It stayed pegged at a normal setting. Ten minutes later I set down at the departure airport and we pulled the relief valve, cleaned it and out came a little piece of carbon. Returned to service a few minutes later with runup ok and proceeded on my way.
 
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JP said:
At a barely turning over idle the pressure on a C-90 is nothing to write home to Mother about. One other thing to check is the oil pressure relief valve, spring and seat. If any little bit of whatever gets in there after an overhaul it will show low pressure.

You can also do some reading here to buttress your list of things to check:

http://www.bowersflybaby.com/tech/fenton.htm
Click to expand...

I make 50psi at idle at 60F oil temp

Glenn
 
IMG_0440.jpgMy C90. Don't know why picture is upside down. I show 14lbs at idle with the oil temp at 180 plus
 

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Appreciate the help. I'll re check the relief valve and try a new gauge and if no change I'll check the pump.
Ive read all I can about this issue but have not seen anything like my 5 psi.
 
JP said:
Interesting. Lots of the C90s over on this side of the border don't so you must have a washer in your relief valve lol....
Click to expand...
Missing galley plug in engine will do that. Inside case. Wrong bearings will have pressure cold drop off as it warms up.
 
Some 0200's would not build oil pressure if you left the vacuum pump drive gear off of the front of the cam because the bolt holes in the cam went into a oil passage .
I know you have a -8 so no vacuum pump drive , but if you used a different cam ?
Doug
 
Doug
i just open up the back of the engine.
I do have an 0-200 cam. What should I look for to see if this may be the problem?
 
Galley plug missing?
Any idea if I can test for this or bore scope it with the accessory case off?
I was thinking of pumping oil down the main galley and seeing if it had less than normal resistance to flow. What's normal?
The pump gears look like new.
Ive always wanted to open an engine up. But not like this. Also I'm working outside.
 
I have found this before . I made a pressure pot. Filled with oil had a valve in stalled in oil pressure line in block.with cover off open valve with pressure pot at 50 psi oil will flow in block u will see the leak
 
I was once trying to run in a C-85 that would not make pressure. The case has some welding done during overhaul, and the weld penetrated the front passage that connected the left and right oil gallies. It was fine once that got fixed.
 
Another place to check...

The front accessory gear on the cam MUST be installed or the oil pours out the cam gear bolt holes and dumps the pressure halfway around the crankcase. This happens in the nose of the case and unless you have a vacuum pad or a fuel pump access, you can see it without a split.

Sometimes my weight reduction sickness causes unforeseen problems!

-Jay
 
brown bear said:
sibbeston ,Jay is right ,but you can just install bolts with out the gear.
You might try gntw,s trick , if it is the v/p gear missing on the front of the camshaft then one side of the engine {right side I think ?} will not be getting any oil. There are some drawings on page 122 - 125 of this link that may help . http://www.culvercadet.com/manuals/C85_overhaul_manual.pdf
Doug
Click to expand...

If I remember right? there should be a plug under/below one of the front galley plugs on the case front halves. It is left out if it has a front oil cooler, the cooler passes the oil from the right side to the left side galley. No cooler and the inner plug blocks that passage? They are removed when overhauled

Glenn
 
Thanks for the replies.
Do you think if I pump oil in the front left gallery plug and block the holes at the accessory case, that I will be able to tell if that is the problem? Maybe if I pump oil in my healthy a65 and compare it to the c90?
If I decide I need to take the engine apart (probable) what gaskets should I order? Sump, crank case cover?
Its a zero time engine but I'm a little worried about the 6 or so times I started it (30 seconds). If I did damage it from running it dry do I look for scoring on the cylinders?
One more thought. Once I primed the pump and ran it I checked a previously dry valve cover on cylinder 3 for oil and it had lots. Would this be the case if I was losing oil at the camshaft? So if I'm getting oil to the valves at the #1 cylinder would that prove anything?
thanks
 
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I watched an A65 start dry after sitting for over a year. The axxhole at the controls jazzed the throttle twice " to try to get it to suck up the oil". It started as a standard crank and it took the .020 cut to fix it after that fiasco. That engine still held 25# pressure and would not have been torn down if didn't have over 1800 hours on it. In my opinion if it ran faster than a dead idle for even a few seconds with no oil pressure, the main and rod bearings need looked at. It is obvious something is not right and I think you have passed the point where you need to open it up and double check everything with an experienced wrench looking over your shoulder. jrh
 
You can take the front left plug out and if it has oil on it, then you have no gear. Yes, you can put bolts in to plug the hole. Been flying like that for a while. I did get drilled bolts and safety wire them.
 
Good thread. I have an 85-12 stroker ready to go with new crank and bearings, but ai have always been worried about that front bearing - they are different for pushers, and I am not sure how, but I am not using it as a pusher. Now I shall be looking for hidden gallery plugs that are not plugged, and that front gear on the cam.

I assembled it a long time ago, and am waiting for the current dirtbag 85 to tell me it is getting tired. Now I am sure I am going to at least split the case and look around. Probably has spiders in there by now.
 
The only galley plugs I remember on the small Continental were the two in the front of the crankcase. I just built one up and that was what I found in the parts manual and that is what I installed.
 
There is some plug in the back under the accessory case that is critical when going from a dash 12 to a dash 8 using Don's data, but I am not sure what it is or where it is. We had a similar problem a couple years ago. I was not the mechanic; just the test pilot.
 
In the paperwork I got with the engine it states the engine was modified to accept the 0-200 cam. Any idea what this may have been?
 
If they used a -12 acc case gasket on a -8 it is missing the hole in the gasket that aligns with the oil hole in the acc case and the engine case on the left side.
Last couple pages shows oil flow www.culvercadet.com/manuals/C85_overhaul_manual.pdf

Copy and paste, won't turn active in this post ? ~http://www.culvercadet.com/manuals/C85_overhaul_manual.pdf


Glenn

 
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