8N Carburetor Fuel Drip

bapa20 · Mar 30, 2020

1949 8N - 6 volt electrical
Tractor ran once last year then would not restart
Rebuilt carburetor
After cranking, tractor failed to start, fuel dripped from carburetor

This year, repeated carburetor rebuild, verified float not stuck
Verified spark
Compression 70 psi @#3, 100 psi @ #s 1,2,&4
With fuel on before cranking, no fuel drips from carburetor
After cranking, tractor fails to start, fuel drips from carburetor

Suggestions where to look next? Thank you!

Bruce (VA) · Mar 30, 2020

Your choke rod.

You're giving it too much choke. If the
tractor doesn't fire in 2-3 seconds, pull
the choke out for 2-3 seconds. No more.

Rusty2N · Mar 30, 2020

Needle valve is not doing it's job. I know, good eye for the obvious. Question is why it isn't doing it'job. There are a few
answers, hole in float, float adjust not correct, float hanging up on sides of carb, hinge to tight, for a start.
It has been flooded enough that plugs are coated with gass and might need replaced or at least burn the residue off the
electrode. Once you get clean plugs turn off the sediment bowl valve and see if it will fire on what gas is in the carb. Do
not choke!!
Did you do a wet test on #3 cyl? Could be stuck valve.

bapa20 · Mar 30, 2020

Thanks Bruce. Linkage correct. No success on restart with or without choke.

bapa20 · Mar 30, 2020

Thanks Rusty2N
Verified integrity of the float, float position per spec, freedom of movement on the hinge, freedom of the needle (not sticking). Float appears to be free of contact with the carb but that is difficult to prove.

No change with fuel to the carb shut off. I will verify clean plugs.

My wet test on #3 was after soaking with fogging oil. It did start lower when dry.

Jim L WA · Mar 31, 2020

How did you verify spark? So I won't get too wordy here, go read some previous posts from the last day or so and find Bruce's 75 tips. Pull them up and read them.

bapa20 · Mar 31, 2020

Thank you Jim L WA

I verified spark with a timing light. I will recheck for spark based on 3/16-1/4" gap test.

I did surface and gap the points and I replaced the condenser with a new Echlin based on measuring <1 mfd on the previous condenser. However, the new one reads the same <1 mfd where I was expecting 30-40 mfd by spec.

Thank you for the heads up on Bruce's 75 tips!

deanostoybox · Mar 31, 2020

The I&T FO-4 manual states:
The Ford 91A12300 condenser is of .29-.32 mfd capacity and should have an insulation resistance of 5 megohms @ 210? F. This is for the front mount distributor.

No specification is given for the side mount. The replacement condensers available today and those I have found in tractors with side mount distributors from late 8N through early 1000 series (up through 1964) have measured 0.24-0.27 mfd.

8N Carburetor Fuel Drip

bapa20

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Bruce (VA)

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Rusty2N

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bapa20

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bapa20

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Jim L WA

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bapa20

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deanostoybox

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