Changed oil Jet Star 3, now have no oil pressure . . .

Been hauling / feeding hay all winter with tractor, getting around fairly well with chains (till the snow got too deep). Tractor performing well, no issues at all. Couple days ago had tractor warmed up; drained crankcase & dropped oil filter and went in for lunch while draining. Hour or two later, new filter, refilled (a little too much), started engine: no oil pressure. Since then attempting to verify pressure while cranking engine, no spark plugs: changed gauge (same result), removed press sensor line at oil pump, no visible pressure while cranking, removed oil filter (filter had not filled with oil). Cranked engine without filter on, oil does pump out the port. Installed new oil filter. Drained crankcase oil, put in lighter oil. Still no pressure while cranking with starter. Filter still does not fill with oil while cranking engine, but with oil filter off, cranking engine does pump oil out port. With everything normaled back up, started engine. 30 sec. at idle should've filled filter & built pressure but did not. Shut down. Cannot figure out what is going on here. Oh, and tractor has not been in a warm shop; ambient daytime temp has been in teens & 20s F. Anybody ever encountered anything similar?

Did you pull out releif valve assembly? Sounds like it is bypassing or sump is sealed off.

(reply to post at 18:31:31 02/15/14)

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I had a International Truck with a 466DT engine under the hood, I drained the engine oil on Fri. night and installed a new oil filter on Sat. morn. dumped in new oil and no oil pressure, when I started it. End result was the oil pump lost the prime, to reprime the oil pump I restarted the engine and would accelerate and back off the throttle, I did this for about 1/2 of a minute and it gained prime again, lesson learned, as soon as the oil is drained out, dump in new oil, so oil pump does not loose prime. If your tractor was fine before you drained the oil out, nothing could happen to it sitting there with the engine shut off. good luck

It is the correct filter for the MM 206, isn"t it? If it has a drain back valve it may not work, oil flows the opposite way through the element in some MM engines as most car engines.

-The only thing I can suggest you try from the outside is to pump oil into the guage port on the pump with a sqirt can. Lots of oil. That may put enough oil into the pump that it will prime.

You can also fill the filter- Fill it with oil, let it sit until the element soaks up most of the oil, then put it on.

-You may have to pull the side cover and check the floating pickup in the oil pan. It may have an air pocket in it, or something else wrong with it. I worked on one once ("90s) that had holes punched in the top so it would not float anymore. It was in a Jetstar3 too.

I had a similar problem recently. To get the air out of the pump, I unscrewed the filter and turned the engine over until the oil started leaking out at the filter. That allowed the pump to self prime and the oil pressure returned shortly after reseating the filter.

Got back to tractor this afternoon, after it sat overnight with 5w20 oil in sump. Broke connection where gauge pressure tube connects at oil pump, intending to force oil in backwards to prime pump. But oil came running out when connection opened - looked like a positive development. Replaced filter with one previously oil-filled. Cranked engine with starter, initially no pressure registered on test gauge. Broke off test gauge intending to re-connect to dash gauge. Went to check battery charger; then noticed oil dripping from pressure sensor line. That looked positive - reconnected to gauge. Fired up engine and in short order had 37 psi on test gauge! Appears oil pump did indeed lose its prime after sump was allowed to drain for a couple hours then was refilled with viscous 15w40 at about 20 deg F. Thanks for observations & suggestions!