Low Oil Pressure

[vwglenn]

Hi Glenn,

Any update on the engine?

Kevin K.
Sonex 3300

Yes. Here's what has happened up to today. I ordered a replacement spring/PRV/washer from Jab USA. They sent me the new setup and I promptly installed it. No change but I didn't really expect one as I was grasping at straws and hoping anything would fix the issue. I considered installing a fourth washer as I had read it on a BBS somewhere but I consulted the manual and it specifically says up to three so I abandoned that idea.

I again called Pete to ask him what his opinion was on flying the plane to Shelbyville so they could go over it there. He asked me to go ahead and replace the oil pump gears with a low time unit which he promptly sent me before I pursue the flying route. I got the pump gears in the mail Saturday and went to the hangar to put them in yesterday. The replacement is a bigger set of gears. This is very encouraging except the camshaft is short.

One of these things is not like the other...


New gears test fit...

The old gears fit flush with the end of the cam. The new one, while it seems to fit within the cover and the circumference, sticks out well past the the end of the shaft. I can certainly see how this set of gears would certainly throw a larger volume of oil through the system. I'll have to wait on Pete to get an official answer from Jab before I proceed any further.

Evidently early Jab 2200s and 3300s shared the same pump but that changed somewhere along the line.

[vwglenn]

Here's the verdict. My engine has a 2200 pump on it. What Pete sent me is the correct 3300 pump. I will install it this week and cross my fingers that it fixes the problem (which I think it will). This quote from the Jab Rep in Australia sums my concern about the cam distance nicely, "The 3300 oil pump has always overhung the cam shaft as oppose to the 2200 where the cam shaft overhangs the pump (slightly, and hence the cam shaft cut out on the inside of the 2200 housing)."

The next question that needs to be addressed is... How did that pump get there? Either A: it was done at the factory when being assembled. or B: It was inadvertently changed during the overhaul.

Given the design similarity of the two pumps (100% interchangeable), I can see how this could EASILY happen unless you're intimately familiar with both. Given my engine isn't the only one I know of which has displayed this oil problem, I recommend any 3300 owners check this at your next oil change in case there was a guy asleep at the wheel in Australia and grabbing parts from the wrong bin. Simple to check. Just pull the housing/cover off (4 bolts and easy to get to) and see if the cam is recessed in the gear or there is a cutout on the housing/cover for cam clearance. Simple visual inspection should give you piece of mind and potentially save you some serious $$$.

Cutout on the inside of the cover = 2200 pump (gear is 14mm thick).
Gear extends beyond the cam = 3300 pump (gear is 20mm thick).

[vwglenn]

So having the correct pump on the engine appears to have corrected the problem. Go figure. :roll:

[kevin814]

Hi Glen,

Very glad you got it sorted out. You're taking it better than I would. I'd be very upset. The old gears look unworn, so I would guess they were changed at Jabiru USA during the overhaul, which they should be replaced at overhaul. It doesn't inspire much confidence in Jab Usa. I hope the rest of the engine holds up well. My engine had a bad experience at JabUSA, and now I only work on it myself, since I'm very paranoid now about other people working on it. Camit has a new dealership opening up in the US, so that is good news if my engine needs work that is beyond my abilities.

Kevin