lots of gas in JD 520 crankcase

Coyotefred · Aug 15, 2014

I have a JD 520 gas tractor that ran well for several years, but sat without starting since early 2013. Well I started it up recently and it only started with great difficulty, and then had some pretty nasty backfires. I posted on this site and following some advice, drained the crankcase. What came out was a gas-oil mix that came within 3” of a 5-gallon bucket!

Someone suggested that the culprit was bad sediment bowl diaphragms. I bought an “automatic sediment bowl repair kit” (diaphragms, sediment bowl screen, sediment bowl gasket and valve seat washer), but I haven’t installed any of those pieces yet. I wanted to confirm that this was likely the problem, as well as ask whether there is anything else I should as I make the repair, replace the oil, gas it up, start, etc.

‘Any advice appreciated.

big jt · Aug 15, 2014

The subject line of your post had me thinking Sediment bowl diaphragm. That is the most likely culprit. Actually it being faulty is the only way Gas can get into the crankcase. Either by gas leaking back through the oil line or by it allowing the carburator to flood over.

Yep do a oil change and you should be good to go.

jt

flying belgian · Aug 15, 2014

I'm thinking it is the carb itself. That's what it was on our "B" when the gas all ran into the crankcase. The float in carb rusted out and sunk letting gas fill the cylinders. Then evidently it seeped past the rings into the crankcase. After I replaced the float, changed oil and took plugs out to let cylinders empty it started right up and ran perfect never to have the problem again.

Frank 41 · Aug 15, 2014

Big JT is right on. Take that off and put on a regular sediment bowl with a screw shut off and plug the oil line.

Eldon (WA) · Aug 15, 2014

(quoted from post at 16:20:36 08/15/14) Big JT is right on. Take that off and put on a regular sediment bowl with a screw shut off and plug the oil line.

That is a good way to ruin an engine...it is on there for a reason. Repair parts are cheap to fix it right. I bought a 520 cheap that the guy said would not run so he wedged a board between the tank and the sediment bowl primer button. Ran the engine till it started knocking. Turns out he had tightened the bolt on the oil filter to the point that it broke the oil distribution manifold in the crankcase and starved the engine of oil.

Coyotefred · Aug 16, 2014

Well would a good approach then be to replace the diaphragm pieces and then put some gas in the gas tank--but leaving the crankcase oil plug off--and seeing if you"re still getting gas leaking into there?

If not, we assume that the bowl/diaphragm was the problem, put in new oil, and give it a go?

Eldon (WA) · Aug 16, 2014

(quoted from post at 07:22:44 08/16/14) Well would a good approach then be to replace the diaphragm pieces and then put some gas in the gas tank--but leaving the crankcase oil plug off--and seeing if you"re still getting gas leaking into there?

If not, we assume that the bowl/diaphragm was the problem, put in new oil, and give it a go?

I replaced the diaphragms in mine and it cured it. You should be able to see if they are cracked when you take them out.

Coyotefred · Aug 17, 2014

Well replacing the diaphragms did the trick...runs wonderfully now. Thanks everyone for the help and advice!

lots of gas in JD 520 crankcase

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big jt

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Eldon (WA)

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