F12 Issues

John M · Dec 3, 2011

Let me run something by you guys and tell me what you think. 1937 F12, rebuilt/restored in 97, hasnt ran but maybe 20 or 30 hours a year since, been sitting for 4 months. It supposedly started fine since the rebuild.

Heres what its doing: Wont Start!!! Plugs are new, now! All 4 getting fire to them. 1 & 2 get wet, 3 & 4 arent, unless they are burning the fuel off.

Put carb and mag on my F14, no probelms, my 14 runs, even a little better on that carb. 12 does the exact same thing on my carb and mag. Pulled valve cover to make sure valves were opening, which they are.

Why would on 2 cylinders get fuel, on 2 different carbs or do you think its not firing 1 & 2 for some reason? Plug wires are new from Brillman also.

CRASH3317 · Dec 3, 2011

IS YOUR MANIFOLD CLOGGED ON THOSE TWO CYLINDERS?

teddy52food · Dec 3, 2011

Manifold rusted through from ex & in?

John M · Dec 3, 2011

Manifold if fine, not rusted through or stopped up. We pulled it off for inspection earlier inthe week. Remember this tractor was ran 4 months ago, and started just fine, and the carb and mag work on my 14 fine. Im jst baffled as to why 2 plugs get wet, 2 dont, pull the plugs, ground them out and all 4 fire. They are new, and they also run fine in my tractor. Only thing I havent tried yet is changing out the cap and brushes with mine, that could explain the 2 being wet, but I would think it would at least try to fire, but it wont. Also firing order is correct. Again, this tractor was running.

Super-H-Mike · Dec 3, 2011

I think I would put in fresh gas and try to pull start it ? Have you tried that ?

Tom Fleming · Dec 3, 2011

Well, first off, the intake manifold uses the same 2 ports for all 4 cylinder's intake. So, what happens on 2 will happen on all 4 from an intake perspective.

I know you say the valves are moving, but are you sure they are seating? If you can't even get it to phart, my guess is that the valves are hanging OR the pushrods are bent. Make sure you have full valve travel on all the intakes and exhausts.

Really sounds like a valve train problem to me.

Old-F20 · Dec 3, 2011

im gonna go with sticky valves

Old-F20 · Dec 3, 2011

sounds like your float could be sticking a bit. doe sit even act like it wants to fire?

John M · Dec 3, 2011

Yes, we tried to pull it. All it does it flood. We did get it to once or twice, but thats it.

John M · Dec 3, 2011

While I dont have the specs in front of me, the valves are opening and closing completely, as in, the rockers on all 4 cylinders do get loose at the appropriate times, but I guess those could be not completely seating.

teddy52food · Dec 3, 2011

If you hand crank it, is the compression the same on all?

John M · Dec 3, 2011

It has popped once or twice when pulled but thats it. Both carb and mag work fine on my 14, but if we put my carbs on his, which also does fine on mine, we get the same results.

John M · Dec 3, 2011

It "feels" the same. We are going to check it tomorrow after church.

Tom Fleming · Dec 3, 2011

John, if you have the valve cover off, shoot the valves with ATF, Blaster, or similar. I prefer Blaster in these situations, however, get some sort of light oil on them.

The other thing I have done is to take a small brass hammer, and rap each valve when the push rod is loose. You should see it move, and hear it "snap" back into it's seat. If you are not hearing that "snap", you have rusted valve seats or they are hanging slightly.

IMHO.

Super-H-Mike · Dec 3, 2011

I agree a compression test would be a good next step, that will eliminate or confirm the sticky valve theory.

John M · Dec 3, 2011

Ive done that plenty of time myself. This one really has me baffled! If its not the valves, Im not sure what else it could be. I also am stumped on why 2 plugs are getting wet, the other 2 arent, all 4 fire, and the parts we swapped work fine on my 14. The guy Im helping with this pulled all the pusrods, and says they are all straight. I guess the comp test will tell me if something else it wrong!

Ron Weber · Dec 3, 2011

John,

I have had this happen before. A f12/f14 should be a easy starter and a good runner. If it is not, then you have start at the beginning. Biggest problem is that you have not seen it running. OK....here"s the steps I go through:

1)Timing: Make sure the cap is not the problem; I prefer to change caps just to make sure. The old ones are very pourous and will allow shorting if they have any humidity.

2)Make sure the firing order is correct: 1-3-4-2

3)Make sure the timing is is correct and not 180 degrees out of time. Done that embarassing thing a bunch of times. I cranked my arm off once and then found I was off on time and order. Flooded it out big time.

4)Make sure a mouse has not plugged up the intake port. 1&2 are are on the front intake port; 3&4 on the rear.

5)Make sure the float level is correct; bowl free from dirt and varnish

6)On new rebuilds or when they sit too long, I pull the plugs and drag it (pull start) for a couple hundred feet to get it all freed up. Put in a little WD-40 in the cylinder to free up the rings for compression. Then replace the plugs and try to start it.

rhtx55 · Dec 4, 2011

I would first check & service the lil springs & contacts in the mag cap.
After setting a while they build up moisture & corrode or stick without making contact, this may cause your two plugs dry, two plugs wet condition. A dilema I learned on a 36 F20.

Go through the fuel system, sounds like the pump is working but the carb won't regulate the fuel level. Possible sticking float, (and) or needle & seat.

C. M. Allen · Dec 4, 2011

Sounds like to me the plugs aren"t burning off the fuel air mixture. I think your wires went bad. Plugs may be sparking when grounded but how hot is that spark. To test just switch them around. I had this problem in one of mine. Embarassing when a good friend discovered what it was.

F12 Issues

John M

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CRASH3317

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teddy52food

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John M

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John M

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