Ford 841 Runs rough & cuts off

[LReed]

OK, I am pulling out what little bit of hair I have left, so any suggestions will be appreciated.

I have a 1962 841 Powermaster, gas, that has run a little rich as long as I've owned it, but it ran fine otherwise. The last time I used the tractor, I barely made it back to the barn because it started running rough, cutting out. Playing with the throttle I was able to limp it back. Now it will crank, but idles very rough, if you try to give it gas, it cuts off. It will crank right back every time. I've got good spark, clean breather, fresh gas, & pulled & cleaned the carburetor. I don't want to just throw parts at it until it runs, I want to figure it out & fix it. I was certain it was a fuel issue, but now not sure. Ideas?

 

[Steve in IL]

Quick test... Remove air filter hose at carb... Using an old spray bottle, spray some good gas into the carb throat. Try to start. If it fires for a bit, you
have a fuel supply issue. With some care, you will likely be able to actually keep it running by spraying into the carb, while running. Sometimes just doing
this will actually solve a partially blocked carb fuel circuit. After running like this, if it still does not want to run on it's own, check for good fuel flow
coming into carb, by loosening fuel line. If you are getting good flow from the tank, then time to look at the carb. Before tearing it apart, I would try
opening and closing the fuel air mixture needles a few times. (Be careful to open and close them the same amount, returning them to where they started.) This can
help dislodge some small debris.

 

[Eman85]

Did you do a fuel flow test to see if the fuel system is clear? Remove the fuel line from the carb or if it has a plug on the bottom of the carb remove it. Then open the fuel and see how long to fill a pint.

 

[LReed]

Thanks Steve, I've checked flow from the tank to the carb, and all is well. I took the carb apart, soaked it, blew it out, checked all the jets, it's good. I'll pull the air cleaner hose & see if it makes a difference.

 

[LReed]

Yes, gas flows freely from the supply line, and the drain screw on the bottom of the carb. I replaced the gaskets too, not an air
leak.

 

[rvirgil_KS]

Have you checked your points and gap?

 

[Steve in IL]

I guess I just try to diagnose and work an issue like this in a way that starts simple (and cheap), and eliminates potential issues along the way. I should have mentioned in my first note that you should try to start it after pulling the air cleaner hose. If it runs then, you have an up stream air restriction issue. But if it still does not run, try spraying in some fuel. If it still does not start (after spraying in considerable fuel, to essentially enrichen the intake mixture), pull a plug. It should be wet with fuel. Oh... also by the way, do not make the mistake that I have made... make certain your key is on the ON position during all of these tests. My dad's 641 will crank (but not spark) even with the key off. Keep us posted with what you find, and good luck!

 

[LReed]

No, I used a test light to make sure the points were opening & closing properly, bu have not measured the gap.

 

[LReed]

Thanks Steve, I'll post what works for sure.

 

[old]

Point gap can cause odd problems so that is a good thing to check. Should be 0.025. Point gap can effect timing by the way. You also need to have a good blue/white spark that will jump a 1/4 inch gap at the center sire of the cap and at all 4 plug wires

 

[LReed]

This is what I've done today. Checked compression, 142 - 145 psi across all 4 cylinders, & gapped (0.025) & installed 4 new
Autolite plugs. The tractor started right up, and ran great for about 10 seconds, then it spit, sputtered, & cut off. If you try
you pull out the choke, it will cut off immediately. I'll try to upload a video so you can hear what it's doing.

 

[LReed]

Video

 

[LReed]

If someone can tell me how to get a video to load I'll put it up. Won't work for me.

 

[LReed]

Thanks Old, Ill check the gap too.

 

[old]

I have found that now days autolight plugs are not all that good. I use NGK3112 plugs in my Ford tractors

 

[Steve in IL]

Man, that really sounds like a slow fuel delivery issue. Perhaps the float valve is partially plugged?

 

[Steve in IL]

I just had a thought... Perhaps I have seen this... Disassembled carb on our 4000. When I put it together, I installed the float upside down. You might want to check that. One further thought... You have verified fuel flow at the fuel line going into the carb, right? But is there a float drain plug/valve on the float bowl? If so, perhaps open that up to verify continued flow into the bowl.

 

[LReed]

You can't install the float upside down on this one, it won't fit. It almost acts like it's getting too much gas, and flooding itself down. I wish I could get the video to load, it really is hard to explain.

 

[LReed]

Video

 

[LReed]

OK, Tell me what this means! I removed the air cleaner hose from the carburetor, and it was full of raw gas. The fuel was shut off
at the tank, or it would have been more! SO, when I turn the gas on, it flows freely, and keeps on flowing, flooding the engine.
Stuck float, needle valve? I feel like I'm getting close now.

 

[Steve in IL]

You are close! Likely stuck float valve. We had a JD B that did the same thing. Run with fuel turned off at tank, until it starts to stumble (bowl empty). Turn fuel on at tank, until it starts to sputter (too much fuel). Turn fuel off at tank. If you can keep it running like this, your float valve is not doing its job. Could be the float is not floating, or the valve is not sealing.

 

[LReed]

I removed the float & submerged it in a jar of gas for 2 hours, no bubbles, and when I removed the weight, it popped up immediately, shake it, no gas inside, so the float is not waterlogged. Im going to replace the needle valve, seat, & gasket today, IF I can find them locally.

 

[Eman85]

If it was stalling rich it would smother down and the plugs would be wet and very black. Turn the fuel on and start the tractor and shut the fuel off and see if it runs longer as it won't be flooding and will stall lean.

 

[Steve in IL]

Is it possible on that model to assemble the carb without the float bowl, install, hook up fuel, and manually hold float up, to see if gas flow stops?

 

[LReed]

FINALLY! Sorry, it took a while to get my parts in. After rebuilding the carburetor twice with no change, I started looking at air
& spark. Air is good, & I had spark, but the points were worn pretty low. I replaced the points, capacitor, & rotor button, & she
runs like new again. I keep reminding myself of the old KISS saying, Keep It Simple Stupid! Start with the easiest, cheapest fix
first. Thanks to everyone for your input, those that said Points were dead on, and on a positive note, I can remove, rebuild, &
reinstall an updraft carburetor in no time flat! LOL