720 deere getting fuel in the crankcase

deerenutz52 · Mar 5, 2016

Looking for some help. My 720 has been collecting quite a bit of fuel in the engine oil. I have removed the covers and run the tractor looking for leaks as the service manual describes, but don't see anything. I removed the transfer pump and don't see evidence of a leak, not that it wouldn't be possible, but don't see any trace of fuel around the shaft or anywhere. What I haven't been able to find out is where do the return lines from the injector nozzles return the fuel to? They seem to just dead end into the cylinder head, and the service manual I have mentions nothing about them. Also since I don't see any fuel leaks, is it possible for the fuel to be leaking into the oil that lubes the injector pumps, and if that be the case, does anyone know a good place to send them to be rebuilt?

Blksmok · Mar 5, 2016

Look on the bottom of your transfer and there is a small weep hole that is usually plugged. If the primary seal leaks diesel it's suppose to exit through the weep hole rather than go into the secondary seal and eventually into the crankcase. If the weep hole is clean and you do not see diesel fuel coming out, then your leak is somewhere else.

Dieseltech · Mar 5, 2016

Fuel leaks can be at the transfer pump as mentioned. Just returned a 730 pump assembly with injectors that had one rack stuck, both internal valve gaskets eroded and needed replaced, leaks are caused there too and can't be seen as they leak internally by the rack. Few years ago did have a tractor with a pump body split lengthwise, that's not common though. The injector return lines don't go back to the tank, but into the head intake port on the two cylinder diesels.

buickanddeere · Mar 5, 2016

The high pressure lines can leak anywhere from the injection pump to the injectors.

Kent Petersen · Mar 5, 2016

The return lines dump extra fuel into the intake ports

deerenutz52 · Mar 5, 2016

Thanks for all the feedback. I'm thinking I'll have to send the pumps out somewhere to be checked out. Anybody know a good place to send them?

Dieseltech · Mar 5, 2016

I'll send an E-mail. In case it fails call 574 893 4172, be glad to give you a quote. Have the Woodring & Wise JD two cylinder stand with the mounting brackets for all the two cylinder diesels up and running again.

Trkr · Mar 5, 2016

You can get a strong red dye to put in your fuel tank,and watch your lines for leaks.We used to do this years ago with the old two stroke GM Diesels,as they could have issues with leaking fuel from internal jumper lines

720 deere getting fuel in the crankcase

deerenutz52

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Blksmok

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Dieseltech

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buickanddeere

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Kent Petersen

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deerenutz52

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Dieseltech

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Trkr

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