Farmall 400 missing

Bill in IL · Dec 22, 2014

I can't seem to get this one figured out. Tractor has a miss when under no or light loads. Under heavy load it straightens up and runs and pulls great. It seems to get worse as it warms up. I have been through the ignition and carb. I set the total timing with a light cause I wanted to see if timing was jumping around it was steady and set at 25 degrees. I set the valves the other day thinking it would help they were loose and needed adjustment anyways.

leon · Dec 22, 2014

Could be worse, I thought at first that you meant the other kind of missing - like gone!

Cory Schmidt · Dec 22, 2014

What type of fuel are you using? Sounds about like the problem we had with the tractors here on our farm. The problem was we had got a batch of fuel with ethanol in it and the ethanol was igniting early when hot. When that tank full was gone, we told the fuel supplier NO ethanol. When the truck got to the farm; talking with the driver he said lots of the tractors in the area were having problems with ethanol fuel. Been running without ethanol since, with no problems since.

Wayne in MN · Dec 22, 2014

Check the intake-exhaust manifold; I had an H that ran the same way. Turned out the left side intake runner was completely broken off. It was not a visible crack until I removed the manifold & it fell apart.

Bill in IL · Dec 22, 2014

I have thought about that one. I tried the propane test with no results. Maybe I should just get a gasket and pull it.

rustyfarmall · Dec 22, 2014

(quoted from post at 06:11:07 12/22/14) I can't seem to get this one figured out. Tractor has a miss when under no or light loads. Under heavy load it straightens up and runs and pulls great. It seems to get worse as it warms up. I have been through the ignition and carb. I set the total timing with a light cause I wanted to see if timing was jumping around it was steady and set at 25 degrees. I set the valves the other day thinking it would help they were loose and needed adjustment anyways.

Most likely the distributor is worn and needs to be rebuilt with a new shaft and bushings.

Bill in IL · Dec 22, 2014

Distributor is worn some of course for a machine of its age.
On my 560 before I replaced the distributor I could see the
timing jumping all over the place with a light on the crank
pulley. I see no real evidence of that here on this tractor.
Timing appears to be pretty solid.

Hayrack · Dec 22, 2014

I have had a couple tractors act like that and both of them ended up being a broken valve spring. I would do a compression test and see if a cylinder is low.

DaninKansas · Dec 22, 2014

You just described the exact opposite of what ethanol does......

pete 23 · Dec 22, 2014

It is either leaking intake manifold or leaking valve. As you come under a load, the butterfly in carburetor opens up and a whole lot more air fuel mixture comes in to cylinder. If you have a slightly leaking valve there will still be enough air in cylinder to compress and fire. Same with manifold. Time for compression test and complete check of intake manifold.

used red MN · Dec 22, 2014

Broken intake has been mentioned, but could be gasket or loose manifold to head. Spray starting fluid around manifold head mating area at idle and see if it changes the way it runs. If so direct spray to pin point the problem.
Edit by used red: I see you used the propane test, same theory as starting fluid.

CenTex Farmall · Dec 22, 2014

Check for a weak valve spring(s).

mkirsch · Dec 22, 2014

(quoted from post at 06:54:58 12/22/14) What type of fuel are you using? Sounds about like the problem we had with the tractors here on our farm. The problem was we had got a batch of fuel with ethanol in it and the ethanol was igniting early when hot. When that tank full was gone, we told the fuel supplier NO ethanol. When the truck got to the farm; talking with the driver he said lots of the tractors in the area were having problems with ethanol fuel. Been running without ethanol since, with no problems since.

That doesn't make sense because the ethanol has a HIGHER octane rating than regular gasoline, and ignites LATER, like a high octane premium fuel.

Not to stir the ethanol pot again, but it sounds like more of the same old "can't figure it out, so blame it on ethanol" malarchy that has been foisted on the public for the past decade or so.

More likely, your fuel supplier was filling your tank with low-grade low-octane gasoline spiked with ethanol to bring the octane test up. Except, they're probably skimping on the ethanol.

By switching to no-octane fuel, you are getting higher octane gasoline that won't detonate early.

David G · Dec 22, 2014

If you are talking about idle advance, that is to high. I would want to see 10-15 at idle and low 30s at full RPM. To much idle advance will cause a roughness.

Cory Schmidt · Dec 22, 2014

could of been firing late(either way it was missing like crazy). But we did a simple test. drained the fuel put in non ethanol ran fine, drained it again and put in the ethanol blend(from a different place): missing. it was just a suggestion since others in my area were having the same type of problem with ethanol. I don't want any arguing/ complaining either over type of fuel. And thanks all of you that "chewed" me out over that, I did need that (I was just guessing it was firing early)

Bill in IL · Dec 22, 2014

25 at WOT set according to the book. Idle was about at TDC

Bill in IL · Dec 22, 2014

Got another update. I went out to do a quick compression check. Found 1,2,3 at 135psi and number 4 at 125 psi. Odd but it's close enough for now.

When i removed the plugs number one and two spark plug electrodes were mashed down. One was almost shorted after I fixed that tractor runs pretty good. I will test drive it tomorrow if its not raining. I have to take the blame for that. I replaced plugs as one of the first things. Usually I am real careful about that and have never bent one before. So I must have had some ignition problem before and then created one after.

The important part is it appears to be fixed.

pete 23 · Dec 22, 2014

Well, looks like we all missed on this one so I won't charge for my misinformation.

Cory Schmidt · Dec 22, 2014

Funny how little things like that make a world of difference in both performance and the answers you get when asked.

David G · Dec 22, 2014

You did not mention you changed plugs.

You could probably gain some performance if you advanced the timing 4 degrees. This will work unless you hand crank, which should be 0 initial, or a high compression engine which should have about 25 total.

Bill in IL · Dec 22, 2014

I still wonder about those valves on number 4 though. Compression slightly lower and can't get a good idle out of this tractor. Idle is good enough for now but not as I would like it.

I still appreciate the misinformation it was a year of frustration on this tractor solved in a day of random advice with poor backround information given.

pete 23 · Dec 22, 2014

By the way, I like the way you checked the timing. That is the proper way, not the by ear method.

Gary Mitchell · Dec 23, 2014

It acts the opposite of what you describe if the intake gasket is leaky. If that is the problem a little load will kill it or at least make it run worse.

Farmall 400 missing

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