9n vapor lock
- Thread starter ab2ma
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Soundguy
Old Timer
- Joined
- Mar 11, 2002
- Messages
- 51,575
- Location
- Central florida
- Tractor
- RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
If your fuel system is oem.. I'd be real surprised that it was vapor locking unless a few real specific criteria were present.
What is leading yuo to believe that it is vapor locking.
You do realize that it is a gravity feed fuel system, and when the carbs fuel bowl is empty, the flotat drops, thus opening the needle.. with that needle open, there is a direct patch from the fuel tank, thru the fuel sediment bowl top and mid filter, thru the fuel line, thru the carb elbow filter, and into the carb bowl, thru the needle. Also keep in mind there are venturi tubes feeding of fthe carb bowl that are under manifold vacume... That makes it really, really hard to have vapor lock on an oem fuel system on the N.
Now.. what do you have? Cobbled up half metal and half rubber lines?
An extra in line filter because your tank is rusty?
Have you cleaned all 3 fuel screens?
Have you pulle dthe carb bowl drain to see if there is fuel in the carb, when you think this vapor lock is happening.... ( could be a stuck float, not opening the needle... )
On very rare occasion, people running lean, and/ or advanced timing, and/or with a hole in the manifold, can cause some fuel line problems, and some tank boiling.. however these are self inflicted problems, and easy to correct.. or if not correctable at the time, .. temp heat shields are real easy to fashion.. etc.
Post back. Also provide details as requested in the body of the message as well as here:
What carb? OEM tsx 33 or does it have a 241 variant?.. or one of them alien zenith jobs?
What are the specific symptoms you are seeing that lead you to believe it is vapor lock? You run it, shut it down, and then can't get it to restart without it cooling? That's the number one complaint I hear people say about the front mount distribuitor N's, thinking it is vapor lock, when in reality.. 98.5% of the time it is spark related...
Soundguy
What is leading yuo to believe that it is vapor locking.
You do realize that it is a gravity feed fuel system, and when the carbs fuel bowl is empty, the flotat drops, thus opening the needle.. with that needle open, there is a direct patch from the fuel tank, thru the fuel sediment bowl top and mid filter, thru the fuel line, thru the carb elbow filter, and into the carb bowl, thru the needle. Also keep in mind there are venturi tubes feeding of fthe carb bowl that are under manifold vacume... That makes it really, really hard to have vapor lock on an oem fuel system on the N.
Now.. what do you have? Cobbled up half metal and half rubber lines?
An extra in line filter because your tank is rusty?
Have you cleaned all 3 fuel screens?
Have you pulle dthe carb bowl drain to see if there is fuel in the carb, when you think this vapor lock is happening.... ( could be a stuck float, not opening the needle... )
On very rare occasion, people running lean, and/ or advanced timing, and/or with a hole in the manifold, can cause some fuel line problems, and some tank boiling.. however these are self inflicted problems, and easy to correct.. or if not correctable at the time, .. temp heat shields are real easy to fashion.. etc.
Post back. Also provide details as requested in the body of the message as well as here:
What carb? OEM tsx 33 or does it have a 241 variant?.. or one of them alien zenith jobs?
What are the specific symptoms you are seeing that lead you to believe it is vapor lock? You run it, shut it down, and then can't get it to restart without it cooling? That's the number one complaint I hear people say about the front mount distribuitor N's, thinking it is vapor lock, when in reality.. 98.5% of the time it is spark related...
Soundguy
thanks for the reply.the 9n works great for about a hour then shuts down.it has spark to all 4 cylinders.also when i pull the drain plug on the carb a steady stream of gas is present.the plugs appear dry also.when it cools down it starts and acts normal.the carb is a rebuild from central tractor,but had problems before installing it.any help appreciated,stan
Soundguy
Old Timer
- Joined
- Mar 11, 2002
- Messages
- 51,575
- Location
- Central florida
- Tractor
- RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
ab2ma said:
Your answer is in your response. If you can pull the carb drain, and fuel comes out.. you can't have a vapor lock.
Really sounds like you have an overheated front mount ignition coil.
If this is still an OEM 6v positive ground tractor, then it used the oem 6v ignition coil, and a ballast resistor that is mounted to a 3 terminal wafer board on back of the dash. Without this ballast resistor, the coil overheats and spark potential drop senough to let it stall, due to internal shorting in the coil. As it cools, the coil comes back to life.. etc. Observing spark in open air is not like observing spark in a compressed cylinder... A weak spark can jump an open air gap where a weak spark may not jump a compressed air gap.
Verify that your ballast resistor is in place, and inline with the ignition switch, and is not bypassed.
if this is a 12v converted unit, you will need the oem balalst resistor and an 8ne10306 dropping resistor, with the oem 6v coil. OR you could get a newer tisco style 12v coil, and then instead, use a 1/2 ohm 20 watt dropping resistor in line with it. You can make the resistor using a radio shack and get a 2-pack of part # 271-131 1-ohm/10w power resistor. Wire them in parallel ( back to back ) and then you will have the 1/2 ohm 20 watt resistor.
Also.. these old ignition systems need metal core wires.. not modern auto carbon core supressor wires. The oem plug was a champion h10.. For modern no lead gas, try a champion h12.. or better yet.. an AL 437.. its a 1 range hotter plug.. and doesn't fould as bad as the h10 ( or the h12.. ). Points are set at .015
Post back with more info.
Soundguy