Ford 8n surging

[Dal47]

My ford 8n started surging and I replaced the fuel tank with a new one, new tsx241b carb, new fuel shutoff valve, new fuel lines. The tractor still surges.
If I remove the mail needle valve completely from the carb the tractor runs just as smooth as can be and has lots of power and no surging. I then put on
another tax 241b new carb and the same thing happens. Surges at half to full throttle idle fine put under load starts surging badly remove the main jet
runs smooth again
Forgot the 8n is a side distributor engine.

 

[Tall T]

(quoted from post at 13:42:51 04/07/20) My ford 8n started surging and I replaced the fuel tank with a new one, new tsx241b carb, new fuel shutoff valve, new fuel lines. The tractor still surges.
If I remove the mail needle valve completely from the carb the tractor runs just as smooth as can be and has lots of power and no surging. I then put on
another tax 241b new carb and the same thing happens. Surges at half to full throttle idle fine put under load starts surging badly remove the main jet
runs smooth again
Forgot the 8n is a side distributor engine.

Surging is characteristic of lean burn.
The side-pointing idle mix is [b:442373dcf5]out[/b:442373dcf5] for lean, [b:442373dcf5]in[/b:442373dcf5] to enrich.

 

[Dal47]

I turned this screw all the the way in no change. I removed it completely no change. I removed the main needle completely the tractor runs perfect
under load. I put my finger over the main needle valve hole and the tractor surges again. Remove all needle valves the tractor runs fine. Put my finger
again over the main needle port with all needle gone and the tractor surges.

 

[kdbenton]

It could be that the timing is advanced too far.
back it up a little and see if your adjustments start working.

just an idea

 

[soaked]

Hi dal47, suggest measure the economizer jet. Spec for the stock, Marvel Schebler carb is .046. The jet in my aftermarket, silver carb was .065.
The bigger hole in the jet lets engine pull to much air from the float chamber, giving your symptoms.

Welders torch cleaner wires have published wire sizes, and inexpensive.

Check out post yesterday " fixed cheap aftermarket carb"

In the pix below, zoom in to see the correct 9n9914 jet on the small wire.
The .065 jet is on the large wire.

The screw driver points to the economizer port, where the jet is screwed in.

Please post findings.

John

 

[jimtrs]

(quoted from post at 16:42:51 04/07/20) My ford 8n started surging
I replaced the fuel tank with a new one
new tsx241b carb
new fuel shutoff valve
new fuel lines
The tractor still surges.
If I remove the mail [b:8ca3235c06](MAIN)[/b:8ca3235c06] needle valve completely from the carb the tractor runs just as smooth as can be and has lots of power and no surging

Surging can be caused by running too lean. By removing the Main needle completely the engine is getting the most fuel possible. Unfortunately it is probably also getting more air. This condition will use a ton of fuel, and cause other problems.

I then put on another tax 241b new carb and the same thing happens. Surges at half to full throttle idle fine put under load starts surging badly remove the main jet
runs smooth again

Still sounds lean. Check for vacuum leaks at carb and manifold, and again at manifold to engine, and throughout the manifold itself. Vacuum leaks cause a lean condition.

A lot of governors have a surge spring to help with surging when everything is adjusted correctly, acts like a dampener. These governors do NOT. Check that your governor tension spring is adjusted correctly, and that there is no EXCESSIVE play in the governor arms. Most of these old Fords will have some play in these arms, but normally do not surge.

 

[Dal47]

Thank you ,thank you ,thank you I can not tell you this enough I put in the smaller economizer jet and the tractor runs perfect.

 

[soaked]

Glad it worked!

 

[Tall T]

(quoted from post at 10:09:47 04/08/20) Glad it worked!

Kudos John!
There must be a lot of folks out there who need to know this fix that you figured out!

Definitely a file worth adding to my Jubilee "Maintenance" folder.

Terry

 

[soaked]

Thank you Terry! 😃