lpg demand valve

[grapegro]

I have made an lpg demand valve using plans from J E Howell. The valve kit comes in pieces and not assembled. In this kit is a soft material seat for the valve. The seat has a groove on one side and a flat on the other. Could someone please advise me as to the correct placement of this seat and any other help you may have.

Regards Norm

 

[Rustkolector]

Norm,
The spring loaded valve seats against the grooved lip side of the soft seat. Press it in place with a flat ended piece of full diameter shafting so as not to mar the seat lip. The diaphragm metal center with the little doughnut side seats against the projecting valve needle. Don't forget the priming button. It is used to purge the fuel line and primes the engine for starting. If you have done it all correctly, using your mouth, you cannot blow into the "inlet" fitting, and you can suck air out of the "outlet" with the slightest suction on the "outlet" fitting. Pressing the priming button should allow free flow through the demand regulator. A Weber "Go Anyware" 1lb bottle regulator (Ebay) is compact and provides all the pressure you will need.

Jeff

 

[grapegro]

Hello Jeff,I have done the tests as you suggest and all checks out okay. The problem I have experienced is after initial testing, there is a leak from the relief hole in the top of the valve housing. I consider that gas is by passing the seal. Thank you for your help. And I hope others may find these clues of value. Not ever been successful in downloading pictures to HMEM, I will try and do so when I get the unit working properly
Norm

 

[Rustkolector]

Norm,
The neoprene seat should not be loose in the hole. It should be an interference fit enough to self seal it from leaking. If so, No 2 Permatex should seal it. It is also possible that the spring hole depth is too deep not allowing the spring tension to hold the needle firmly against the neoprene seat enough to shut off the flow of gas. That hole depth is critical to proper operation. The vent hole you refer to is where the priming button should be. If it is there, depressing and releasing the priming button should visibly show the button popping back up into the shutoff position if the spring is doing its job properly. Also check the diaphragm for holes.

Jeff

 

[canadianhorsepower]

Norm,
The spring loaded valve seats against the grooved lip side of the soft seat.
Jeff

Jeff
it's the other way around the small ring
in the seat goes in the bottom
or away from the needle.

cheers
Luc

 

[Rustkolector]

Luc,
You could be right. When I was looking for this very information many years ago a model builder told me the lip side was the needle seat side. That model builder's engines ran nicely so I have built all my regulators the same way, and mine all run fine. Hence, my recommendation. I'm not sure Tecumseh even used these parts for LP fuel. The needle does seat deeper on the solid side which would change spring pessure. I guess you could try it both ways and see which works best for the carb & engine combination. Either way, Norm's regulator should not leak fuel with no vacuum signal on the inlet.

Jeff

 

[canadianhorsepower]

Luc,
You could be right. When I was looking for this very information many years ago a model builder told me the lip side was the needle seat side.

I work in a small engine shop and we install about 50 of them a week

That model builder's engines ran nicely so I have built all my regulators the same way, and mine all run fine. Hence, my recommendation. I'm not sure Tecumseh even used these parts for LP fuel.

You are wright they will work both ways but if you look at it closely you can see that the side with the lip is wider then the other side. Tecumseh don't have propane engine they are all converted from outsider

Either way, Norm's regulator should not leak fuel with no vacuum signal on the inlet.

Jeff[/QUOTE]


you are wright there is not suppose to leak

cheers

 

[grapegro]

Hello all,
Ended up sending a reply which was sent somewhere else. My apologies for that.I got my head piece magnifier a couple of days ago a and had a good look at all parts.On the taper of the needle there is a fault in the metal that would not seat against the soft seal, so the cause has been established. I can get a replacement if I send it back to the US. Freight is nearly three times the cost of the needle assy, so will have to bite the bullet and spend more big dollars to replace it. Does any one know of a source for this valve in Australia please. Thank you all for your help.
Norm

 

[canadianhorsepower]

Hello all,
o will have to bite the bullet and spend more big dollars to replace it.

make one on the lathe, put your in the lathe and with a small sand paper or file
clean it up

 

[grapegro]

Hello Luc,
Do not think I can make one that fine, the needle I have has a deep fault in it that would take away a fair amount of metal to clean it up. If I were to attempt to make one, what metal would you suggest I use for it?
Norm

 

[canadianhorsepower]

Hello Luc,
Do not think I can make one that fine, the needle I have has a deep fault in it that would take away a fair amount of metal to clean it up. If I were to attempt to make one, what metal would you suggest I use for it?
Norm

Hi Norm,
I would use aluminium
you would be surprise how easy it's done
the 2 pictures include is for a main jet for a chainsaws
look at the size.

good luck

 

[deverett]

See if you can source a Tecumseh carb repair kit, the parts of which are used in your kit.

Have a look at eBay 190437457298. Only one left, but if you can't find any others, look at eBay 141483704268. I know you don't need all the parts, but perhaps cheaper than your present situation.

Dave
The Emerald Isle