Ford 850 Tractor running bad

[jcisrisen]

I have a 850 Ford tractor that has ran great for two years, now its running bad. Here are symptoms and what I have done so far.
1. Runs pretty good for an hour or so then runs bad.
2. If I pull choke out half way, it will run better.


I have replaced sparkplugs, wires, points. and timed it. Adjusted carb. Seems that after the tractor warms up I am having trouble getting fuel into the carb. Any suggestions?

 

[pete59]

Your carb. has to be cleaned with carb cleaner , make sure you are getting adequate fuel to the carb.I have heard of some Fords that the fuel will have issues when they get warm.Hope that helps.

 

[Ultradog MN]

It sounds like electrical to me.
If it has fuel to run good for an hour it should have fuel to run all day.
Never assume anything. When it starts running poorly immediately get out of the seat and pull a plug wire and VERIFY that you have a bright bluish white spark that will jump at least 5/16". Short or yellowish spark will not do.
I'm thinking you might have a connection somewhere that is corroded or loose and after an hour it heats up and begins to lose connectivity.
When was the last time you went over the tractor and serviced all your electrical connections.
Take them all off one at a time and clean/polish the connector and the post. I like to use a 1/2" fitting brush for that. In fact I keep one in the tool box on both of my tractors. See photo
Remember the mantra: "Keep em clean, bright and tight."
You can also make up a jumper wire with alligator clips on both ends and when it starts to bad run the wire across the key switch to test it. Those key switches are not entirely robust and do fail. If that doesn't help it run better then use your test wire and go directly from the battery to the coil and see if that helps. Don't run it that way for more than 10 minutes or so or you will burn your points. If the running improves you know it is electrical and not fuel.
Sort out your electrical/spark FIRST. Only then go on to fuel/carb.

Edit: Remember, pulling the choke out will enrich the fuel mixture allowing even a poor spark to fire the rich mixture.

 

[jcisrisen]

Thanks for the replies. I will do the spark test. I did take of the carb to see what model number it was. Figured I would go through it anyway. Its pretty dirty and I haven't touched it for 3 years. It's a Marvel Schebler. Tsx 593

I replaced the plugs this year along with points and timing. Last year plug wires. Anyway....I can get a rebuilt tsx769 pretty reasonable...would that one work??

Does electronic ignition work well on these Fords??

 

[Soundguy]

heck spark. if spark is great.. then move on to fuel.

also ensure you are not getting a tank vacume

 

[jcisrisen]

I just overhauled the carb and actually am replacing a cracked manifold that I noticed when taking off the carb tomorrow. As far as avacuum problem...is that a gas cap issues or what would cause or how could I diagnose that??

 

[Ed L]

The gas cap is vented to allow the fuel to drain to the carb, over time it can get plugged.

Ed

 

[Soundguy]

if it does get plugged, and easy fix is a drill bit and loose fitting pop rivit.

 

[jcisrisen]

Thanks guys. Ill clean, drill, or replace the cap. I did once try unhooking my gas line and allowing the gas to gravity flow out. I had a good turbulent stream but I cannot say it was a solid stream...should it be. One thing I have noticed in regards to the gas tank is a fine "Bubbling" after long use. For instance...I mow for a couple hours or so...then I open the gas tank to fill and there are very tiny bubbles streaming to the surface through a couple inches of gas from the center. I thought maybe I was boiling my gas...but I felt it and it was only warm. I also checked the screen and its clean. Just seemed kinda wrong. Ill report back next week after I get the carb/exhaust manifold installed and check the cap. I also replaced the inline filter connected to my sediment bowl. I had also checked the intake manifold with propane and couldn't find a leak there... thanks again.

 

[Soundguy]

ethanol will make gas boil badly.. make sure the heat shields are in place.