John Deere 720 LP

deerenutz52 · May 13, 2013

Ok I'm reaching out there for any help I can find. I have a 720LP that I aquired and can't seem to get it to run. If I turn the gas on to it let it sit about 5-10 seconds it will putt a couple times then die. I have rebuilt the m-4 converter and it seems to be working properly now and the carb has also been gone over. (actually tried 2 different carbs with the same result) I have found numerous problems incuding the timing being off, a sticking valve, and all have been corrected. It has compression, maybe not the best (about 25-30psi) but i feel it should fire. Currently I have the strainer bypassed and am trying to fire it off of a gas grill tank and the only thing I can figure is that this won't supply enough gas? Any help would be greatly appreciated!!

Tx Jim · May 13, 2013

Is the oil level in the air cleaner at the full mark? Have you changed the fuel filter?

TheJDWorkmen · May 13, 2013

New propane tanks will not provide enough flow try finding an older tank. We ran in to the same issue

Andy C · May 13, 2013

I am thinking 25-30 psi is VERY low for compression. I have run our both our 7o & 730 LP off of grill tanks (ran out of fuel in the field)It was warm and don't know that we could have plowed but they both ran good enough to get them home. Have you tried the tow it around the field method? sometimes a low compression engine will start by towing it off! Let us know what you find!
Andy

bingo · May 13, 2013

Have run a 720 lp for years, check your air intake.

deerenutz52 · May 14, 2013

Thanks all for the feedback, I have tried towing it which is the only time I can get it to fire at all. (The starter don"t work to well) The air intake does flow air freely and the oil was replaced and filled to the proper level. I know the compression is low, but the little it fires it seems to hit pretty strong which tells me its got enough to run, so it would seem to me to be a fuel problem(However I"m new to the LP"s.) The filter is bypassed and coming straight from the tank so I guess I"m left with finding an old tank or maybe trying to fill the tank on the tractor with my bottle. Again thanks to all for the input, all good suggestions, and I"ll keep you posted after I try the older tank. (If I can find one!)

Dave Gunem · May 14, 2013

I have six 2cyl LP tractors [ 1-730,3-630 & 2-620 ] and have not had any issues with grille tanks . Pretty standard when I get a new one that hasn"t run in a while { seems most fit into this category ] to just hook a grille tank to the convertor to get it going . Used both new and old grille tanks and it didn"t make any difference . Now at full snort this may be an issue but for what you"re doing it shouldn"t be . These things are pretty simple and it sounds like your biggest issue is poor compression . Remember LP tractors are supposed to have more compression than gas ones . The compression you state isn"t enough to run it . When all is well and it hits on a cylinder it will hit REAL HARD .

deerenutz52 · May 15, 2013

Well, thanks to you all for the good feedback, I finally got the 720 to run! Turns out that the the wonderful saftey features that our saftey conciensious government mandates building into things has come into play. The fitting that I purchased to connect to the grill tank has some sort of flow control built into it that only allows a trickle of gas to flow. I punched out the center of it with a drill bit, put it back together, gave the old girl a tug and away it went! Sounds good all except for the thumping noise coming from the flywheel side main bearing.(Just my luck) Looks like its time to start tearing it down, but at least I know where I stand now. Thanks to all again!

dej(Jed) · May 16, 2013

(quoted from post at 15:53:23 05/13/13) Ok I'm reaching out there for any help I can find. I have a 720LP that I aquired and can't seem to get it to run. If I turn the gas on to it let it sit about 5-10 seconds it will putt a couple times then die. I have rebuilt the m-4 converter and it seems to be working properly now and the carb has also been gone over. (actually tried 2 different carbs with the same result) I have found numerous problems incuding the timing being off, a sticking valve, and all have been corrected. It has compression, maybe not the best (about 25-30psi) but i feel it should fire. Currently I have the strainer bypassed and am trying to fire it off of a gas grill tank and the only thing I can figure is that this won't supply enough gas? Any help would be greatly appreciated!!

The grill tanks work just find, new ones or old ones. Plenty of flow to the carb.

buickanddeere · May 16, 2013

The tank worked fine, you did not know how to use it.
Open the tank valve on an empty unpressurized system and the "FLD" Flow Limiting Device. It may do it's job and "close".
Reset the FLD by closing the tank valve and reopening the valve.
The FLD is there for a very good reason.

John Deere 720 LP

deerenutz52

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Tx Jim

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TheJDWorkmen

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Andy C

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bingo

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deerenutz52

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Dave Gunem

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deerenutz52

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dej(Jed)

Well-known Member

buickanddeere

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