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My FIL's 706 LP is acting up lately, he doesn't use it enough and he's got it up for sale, but it needs some attention, I think, so I figured I'd ask here.

The thing runs great, getting it started is the issue. Gotta pull the choke out all the way and just start cranking, it'll crank over probably 30 seconds before it starts. It used to start easier than that.

He says that when you shut off the vapor valve it dies immediately and didn't used to do that, it used to run for a bit after shutting the valve.

Anyway, I don't know squat about LP tractors, there just aren't any around here. He says it's got a Century Model 6 fuel converter on it. I can't seem to find a rebuild kit for it, yet. 

Does anyone know what I need to look for or have any other ideas? Thanks for any help.

 

Travis

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We have a Toyota forklift that was doing similar. I put a kit in the vaporizer, pulled the drain plug and got maybe half an ounce of black liquid out of it. It's been running like a champ ever since. The kit was simple, a couple of gaskets and a strainer.  

I Googled Century Model 6 and came up with CM6 2504 converter Says it's NLA, but shows a C-286-1688 kit.

I would first look for the drain plug and see what happens.

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One reason imparting out my 706 LPG. No one around to work on them and they are worth more parted out than running. Mine still had Ensign vaporizer and was told parts havent been available in decades for those. 

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49 minutes ago, Long Farms said:

One reason imparting out my 706 LPG. No one around to work on them and they are worth more parted out than running. Mine still had Ensign vaporizer and was told parts havent been available in decades for those. 

parts are a available still , just not as easy to get as century stuff

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Vaporizer needs rebuilt as Bleedinred talked about. over time the diaphragm breaks down and leaks.

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1 hour ago, Long Farms said:

One reason imparting out my 706 LPG. No one around to work on them and they are worth more parted out than running. Mine still had Ensign vaporizer and was told parts havent been available in decades for those. 

Everhart LPG had the Ensign parts I needed to rebuild a vaporizer/regulator on a Farmall 400 some 15 years ago.  There was on tiny spring their kit lacked and I was able to find it after some searching.

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Check the fuel flow to the vaporizer/regulator.  if that's good check the ignition system.

the regulator and carb rarely give trouble. Usually it's ignition related and few people know how to set points anymore. It seems the lpg engines are more picky about ignition than gasoline. Also it will probably start easier on liquid during the winter.

Thx-Ace

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20 minutes ago, acem said:

Check the fuel flow to the vaporizer/regulator.  if that's good check the ignition system.

the regulator and carb rarely give trouble. Usually it's ignition related and few people know how to set points anymore. It seems the lpg engines are more picky about ignition than gasoline. Also it will probably start easier on liquid during the winter.

Thx-Ace

we always started ours on liquid summer or winter, always was a hard starter, as said, VERY finicky with points/ignition for whatever reason. Never had troubles with the regulator and it was rebuilt two times in the 30yrs we had it - we always had in the back of our minds something was wrong but thats just how it was, in the winter we just gave it a shot of dynamite juice if not you would grind for hours on it requiring jumper cables. we used a dipstick heater and heat lamp from the farrowing house laid up against the block on it and that helped tons!!!  ours was a 400. 

neighbor had an lp 706, we converted it to gas - it was a finicky starter also lots of choke/lean running and burned valves in it twice 

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As others have said rebuild regulator, have a forklift doing the same thing, parts for regulator should be here today I’m 99% sure this is my problem, good luck.

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If similar to the forklift we have the carburator (or whatever it's called on propane) had worn and the ring had wore into the aluminum bore it moves in and it wasn't making vacuum like it should. We put vasaline in it and it sealed up and started good for that time . We then put a new "carburetor" on it

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This is the guy to ask about propane Screenshot_20200122-133809_Google.thumb.jpg.3a477e4d6c3137f9c382a18085774fd8.jpg

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Beings it dies immediately when you turn off the vapor - more than likely the regulator is needing to be rebuilt or replaced, it should run for a little while after the valve is shut.

Also -

Check the hose between the regulator and carburetor for holes/cracks, if that is leaking it can also hard starting.

If the regulator has a primer button (or electric primer), depress and hold that a few seconds before and cranking to see if that helps.

Those engines are also sensitive to intake leaks causing hard starting, you can check it by using a hose hooked to a propane tank and the valve open while moving it around the manifold/carburetor with the engine idling - when the engine rpm changes you found a leak.

Spark plugs also need to be gapped tighter than a gasoline engine - .016, I've seen guys set them at .035 and the tractor will not start.

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#tonyinca

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2 hours ago, TroyDairy said:

#tonyinca

@Tonyinca

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Someone mentioned finding an intake leak by using a hose hooked to a propane tank and moving it around the intake manifold while the engine is at idle.

 

I would suggest using an aerosol can of penetrating oil in lieu of propane.   Propane is highly flamable-------and would be very sensitive to any type of spark from a running engine (spark from a shorted ignition wire or exhaust spark).    (particularly so if the  tester's name is Sparky!!!)

 

Vacuum is a key ingredient in the operation of a LP gas system-------in that there is a small pressure control valve within the vaporizer/regulator that depends on vacuum to open it in the start up process; plus the vacuum opens the throat of the mixer (same purpose as a throttle butterfly in the carb).  The vaporizer/regulator has a wet side for passage of engine coolant and vaporizing of the gas and a dry side through which the low side vapor pressure passes on to the mixer (carb).

I agree with ACEM----------I have always found more ignition problems than gas related problems when dealing with L-P engines. That said----------do be leary of vacuum leaks including the gas vapor hose extending from the vaporizer to the mixer--------a small pin hole leak or loose clamp has been caused problems for me before.   And------randomly, I have had to clean or install a repair kit in the vaporizer itself.  There is nothing complicated about any part of the system----------just follow your nose.

The button on the vaporizer (mentioned by someone above) releases a shot of raw gas into the mixer)------similar to the old style primers on gasoline engines.

Good luck----

 

DD

 

 

 

 

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Many words of wisdom from delta. I use water in a squirt bottle to check for leaks. Thx-Ace

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