M610 Propane problems

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tima

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Apr 8, 2007
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Hi all. I have a 610 bobcat with the vh4d engine running on propane. Engine runs great for the hours , over 2500. I have tuned up the engine , replaced propane liquid filter , and rebuilt the vaporizer-primary regulator. Sometimes it will start without choking and sometimes not , even when warm. Sometimes it is hard starting period. I thought i had the problem solved after rebuilding the regulator but now it has returned. Also after a hard run when you drop it to idle it may want to die. Air temperature is not a factor. I have noticed icing of the vaporizer untill it warms up but this is not effecting the way it starts. I have the manuals and have set everything to spec's. It has the zenith propane carb and a garretson primary regulator-vaporizer. I guess next i will be looking at re-kiting the carb. Anybody out there had any experience with the propane units. My local dealer has not ben able to help with this one. Any input will be appreciated. Tim
 

Tazza

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I have never worked on a gas setup on an engine before. Have you tried calling mechanics in your area that work on gas cars? I'm sure someone will know where to start.
Can your carb run on petrol still or is it LPG only? There are a few cars over here that run duel fuel. A guy i know that has it on his car starts on gas and runs well, but starts really bad and runs rough at idle when on petrol. I'm sure its just tuning.
I would start on the carb, i'm not sure how it knows when to push more gas in as the throttle increases but i would start there.
I also suspect you have done the usual, replace plugs.
Good luck!
 
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Well, I registered to add my .02..... I'm a forklift mechanic so I have a little bit of experience with LP systems. I am not familiar with vh4d engines or garretson regulators but it all should function the same. The propane in the tank travels thru the hose as a high pressure liquid, thru some sort of lock off valve, electric or vacuum operated, into the regulator which turns the high pressure liquid into a low pressure, often 3-5 psi, vapor that enters the carb that meters the vapor by a diaphragm operated by engine vacuum. The regulator is plumbed to carry coolent thru it in order to prevent it freezing up from the venturi effect from the metering of the high pressure liquid. When the unit is cranking and not starting, try spraying some carb cleaner or flammable brake clean at the carb and see it it catches. If that does not work, try restricting the vapor hose for the propane to the carb. These 2 things will determine if it isn't getting enough fuel, lock off valve bad, or if the regulator is allowing it to flood out, too much propane vapor, bad regulator. If the regulator is icing up, make sure you have coolant, not just water, going thru it and there is a operating thermostat in the engine. This is a water cooled engine, right? Without the unit in front of me, I'm going to guess the regulator is bad. Installing new kits is a 50-50 shot of it working due to the extreme tempurature differences inside it, they warp and crack.
 

skidsteer.ca

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Well, I registered to add my .02..... I'm a forklift mechanic so I have a little bit of experience with LP systems. I am not familiar with vh4d engines or garretson regulators but it all should function the same. The propane in the tank travels thru the hose as a high pressure liquid, thru some sort of lock off valve, electric or vacuum operated, into the regulator which turns the high pressure liquid into a low pressure, often 3-5 psi, vapor that enters the carb that meters the vapor by a diaphragm operated by engine vacuum. The regulator is plumbed to carry coolent thru it in order to prevent it freezing up from the venturi effect from the metering of the high pressure liquid. When the unit is cranking and not starting, try spraying some carb cleaner or flammable brake clean at the carb and see it it catches. If that does not work, try restricting the vapor hose for the propane to the carb. These 2 things will determine if it isn't getting enough fuel, lock off valve bad, or if the regulator is allowing it to flood out, too much propane vapor, bad regulator. If the regulator is icing up, make sure you have coolant, not just water, going thru it and there is a operating thermostat in the engine. This is a water cooled engine, right? Without the unit in front of me, I'm going to guess the regulator is bad. Installing new kits is a 50-50 shot of it working due to the extreme tempurature differences inside it, they warp and crack.
LGS
Thanks for the lesson on lpg. Btw this is a air cooled engine, so how do they keep the carb warm in these applications.
Regards
Ken
 

Tazza

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LGS
Thanks for the lesson on lpg. Btw this is a air cooled engine, so how do they keep the carb warm in these applications.
Regards
Ken
Thats a pretty clever setup! i knew the regulator reduced the liquid gas to a vapour but i never thought it used the engines vacuum, but it does make sense. You learn something new around here every day.
 

tima

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Apr 8, 2007
Messages
8
Well, I registered to add my .02..... I'm a forklift mechanic so I have a little bit of experience with LP systems. I am not familiar with vh4d engines or garretson regulators but it all should function the same. The propane in the tank travels thru the hose as a high pressure liquid, thru some sort of lock off valve, electric or vacuum operated, into the regulator which turns the high pressure liquid into a low pressure, often 3-5 psi, vapor that enters the carb that meters the vapor by a diaphragm operated by engine vacuum. The regulator is plumbed to carry coolent thru it in order to prevent it freezing up from the venturi effect from the metering of the high pressure liquid. When the unit is cranking and not starting, try spraying some carb cleaner or flammable brake clean at the carb and see it it catches. If that does not work, try restricting the vapor hose for the propane to the carb. These 2 things will determine if it isn't getting enough fuel, lock off valve bad, or if the regulator is allowing it to flood out, too much propane vapor, bad regulator. If the regulator is icing up, make sure you have coolant, not just water, going thru it and there is a operating thermostat in the engine. This is a water cooled engine, right? Without the unit in front of me, I'm going to guess the regulator is bad. Installing new kits is a 50-50 shot of it working due to the extreme tempurature differences inside it, they warp and crack.
Thanks for the reply. I have rebuilt the regulator and adjusted it at 12 lbs as per factory specs. The manual shows setting these with 75lbs inlet pressure and 12lbs out. Before i rebuilt it , it would start out at 12lbs and then creep up to 28lbs. The diaphram and metering needle was shot. The vaporizer on a VH4D wisconsin is heated with cooling air from the engine. When i rebuilt the regulator it was pretty nasty inside. Had to soak it in carb cleaner for 3 hours so i can only imagine what might be in the carb. I would guess to say that the demand diaphram or orfice on the end of the carb is probably all dried up and not functioning properly with engine vacuum. When i choke it this would cause more manifold vacuum at the carb diaphram and thus a stronger charge of propane for starting. When it acts up it is still very hard to start even with the choke. The lockoff valve is operating properly and i changed the bronze filter inside. I have a carb kit on the way and will let yall know what happens. As i said engine runs like a champ under all loads , just tempermental in starting. Got to get it reliable for when the snow falls. After 1800.00 initial purchase and about 800.00 in repair parts i think i will have a pretty good machine. Tim
 

Tazza

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Thanks for the reply. I have rebuilt the regulator and adjusted it at 12 lbs as per factory specs. The manual shows setting these with 75lbs inlet pressure and 12lbs out. Before i rebuilt it , it would start out at 12lbs and then creep up to 28lbs. The diaphram and metering needle was shot. The vaporizer on a VH4D wisconsin is heated with cooling air from the engine. When i rebuilt the regulator it was pretty nasty inside. Had to soak it in carb cleaner for 3 hours so i can only imagine what might be in the carb. I would guess to say that the demand diaphram or orfice on the end of the carb is probably all dried up and not functioning properly with engine vacuum. When i choke it this would cause more manifold vacuum at the carb diaphram and thus a stronger charge of propane for starting. When it acts up it is still very hard to start even with the choke. The lockoff valve is operating properly and i changed the bronze filter inside. I have a carb kit on the way and will let yall know what happens. As i said engine runs like a champ under all loads , just tempermental in starting. Got to get it reliable for when the snow falls. After 1800.00 initial purchase and about 800.00 in repair parts i think i will have a pretty good machine. Tim
I too would start at the carby.
Thats a pretty cheap machine too!
 

tima

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Apr 8, 2007
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Hi Got the carb rebuilt and now it starts first time every time and even without the choke. It was pretty dirty inside but i really did not find any bad parts. Kind of got screwed from bobcat though. The carb kit was missing a lot of peices. For instance why would it have the metal caps for the throttle seals but no seals. Only had 1 secondary diaphram , should have been 2. Missing several orings. Missing hard sealing washer for main metering needle boss. The seal for the secondary metering rod was the wrong size also. Funny though that the package was heat sealed unless it had been opened and resealed. I have seen that happen before. I have my bobcat dealer checking the warehouse to see what is going on. Thank goodness i was able to reuse some of the original parts and get it back together and running. I did not take any chances though and pressure / leak tested it with soap before reinstalling it. With that carb nestled down on top off the engine and under the exhuast manifold the last thing i needed was a leak and a fire. The only think that doesn't act right is the idle mixture adjustment. I can ritchen it up but can not lean it out and get the engine to stall. I am used to working with gasoline carbs and i know propane is a different beast. Maybe that is just the way it is. I will try to pick the brains of the local dealers mechanic and see what he says. Any way overall it was very simple to rebuild. Thanks for all the replys and suggestions. Tim
 

Tazza

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Hi Got the carb rebuilt and now it starts first time every time and even without the choke. It was pretty dirty inside but i really did not find any bad parts. Kind of got screwed from bobcat though. The carb kit was missing a lot of peices. For instance why would it have the metal caps for the throttle seals but no seals. Only had 1 secondary diaphram , should have been 2. Missing several orings. Missing hard sealing washer for main metering needle boss. The seal for the secondary metering rod was the wrong size also. Funny though that the package was heat sealed unless it had been opened and resealed. I have seen that happen before. I have my bobcat dealer checking the warehouse to see what is going on. Thank goodness i was able to reuse some of the original parts and get it back together and running. I did not take any chances though and pressure / leak tested it with soap before reinstalling it. With that carb nestled down on top off the engine and under the exhuast manifold the last thing i needed was a leak and a fire. The only think that doesn't act right is the idle mixture adjustment. I can ritchen it up but can not lean it out and get the engine to stall. I am used to working with gasoline carbs and i know propane is a different beast. Maybe that is just the way it is. I will try to pick the brains of the local dealers mechanic and see what he says. Any way overall it was very simple to rebuild. Thanks for all the replys and suggestions. Tim
Glad it was a *simple* fix.
The kit sounds like it may have been robbed before you got it! Most re-build kits have every seal you need to do the whole job....
 
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