Ford 4000 engine rough

[FarmerBlair]

Hi, I recently bought a 4-cylinder gas Ford 4000 at auction. It is a select-o-speed and has 6volt system. It looks good, but had been sitting in storage indoors for years. The fuel was yellow, and engine oil was a nasty creamy caramel-colored mess, as was the oil in the air filter cup. I replaced all that, removed and cleaned the oil pan, etc. Tranny oil looked ok, but changed that as well, and adjusted the bands on the sos which works well.
The problem is with the engine. It runs fine for maybe a couple minutes at 800-1000 rpm, then slows and runs rough to almost stalling out for about 30-60 seconds, then picks up again and runs smoothly. It goes through this cycle continuously. It does this when driving the tractor at higher rpms as well. I've tried adjusting the carb with no improvement. The governor was out of adjustment so I fixed that, and gapped the points and plugs as needed. The points and plug wires are all new looking. Plugs are older and black with carbon but not terrible. I ran out the old fuel and put in fresh, and replaced the sediment bowl filter and seal which pretty much disintegrated.

Compression isn't great: 100-60-70-110 dry (in order of cylinders 1-2-3-4). Wet test raised it to 120-70-90-120. Going to try soaking the rings by adding SeaFoam to the cylinders for a few days to see if it makes a difference. But doesn't seem like that would explain the problem with the rough inconsistent engine cycling. Also, the engine always stumbles when giving it throttle. I spent a lot of time trying to adjust the carb, but doesn't help. I opened the bottom plug on the carb and fuel would freely flow out. The main needle adjust on the carb looks new. The idle adjust screw on the carb (not the idle speed screw) is old, with a little bit of fuel looking like it weeped out at some point during my trying to find a set point. Could a faulty coil be causing the rough running problem?

 

[RM-MN]

Check for the flow of gas to the carburetor. Remove the drain plug from the carburetor and catch the gas in a container. It should run out about a pint in 2 minutes. If not, look for the restriction. It may be the fuel tank cap vent, it may be the outlet screen in the tank, the screen at the sediment bowl, or the screen at the inlet of the carburetor.

 

[redoakroach]

I had this problem with my 860. If the fuel tank and screens are clean it may be some junk in the carb. I drained the carb, removed the main adjust needle and sprayed a bunch of carb cleaner in where the needle goes. I let it sit over night and the problem went away.

 

[Eman85]

Not the best compression on the 2 cyls. I'd do a leak test and see where the compression is going. Wet test didn't restoere compression, so I'd look at valves.

 

[ErnieD]

Old fuel will gum up intake valve guides, try spraying a solvent/gumout into carb intake with engine running. Watch coolant level with center two cylinders being low, may have a head gasket problem.

 

[FarmerBlair]

Wasn't sure what a leak test was, but after looking it up I don't have the equipment to do something like that. Maybe I could adapt my air compressor and find fittings to connect to the spark plug holes, but I don't know. And would probably need another gauge.

So after adding SeaFoam to the cylinders through the spark plug holes for several days, it made no difference in the compression.
I checked the valve tappet clearances and they were way too tight, especially the middle two cylinders (2&3) which had the lowest compression. That is, the gap was near zero. So I adjusted to 0.015-0.016" clearance to all as per spec. This increased compression to 125-90-90-125 psi (cyl. 1-2-3-4). At least it seems easier to start the engine now.

There was a lot of carbon gunk toasted onto the inside surface of the valve cover right over cylinders 2 and 3. I used steel wool to clean up the cover. I'm not a mechanic, but maybe that suggests the valves were not closing all the way at those cylinders? It wasn't like that over cylinders 1&2. There was also a lot of carbon and gunk on the rocker and supports which I tried to wipe off as best I could. I did not remove the tank and tin so space was limited.

I would imagine the valves may be burned from running the machine with the tappets set so tight?

 

[Eman85]

If you have a compression tester that fits the spark plug hole take the hose off of the compression tester and use it to put air in the cylinder. Should only take a simple adapter to allow it to connect to your air hose.
With the valve cover off rotate the ngine and oberve the valve movement to see if they are closing all of the way. Check the valve adjustment on all cyls, if those 2 cyls have no clearance they are probably being held open.

 

[FarmerBlair]

(quoted from post at 10:07:02 04/10/23) If you have a compression tester that fits the spark plug hole take the hose off of the compression tester and use it to put air in the cylinder. Should only take a simple adapter to allow it to connect to your air hose.
With the valve cover off rotate the ngine and oberve the valve movement to see if they are closing all of the way. Check the valve adjustment on all cyls, if those 2 cyls have no clearance they are probably being held open.

Eman, thank you for the tip. I will try doing the leak test using the compression tester hose.

I did adjust the valve clearance on all the cylinders. Those two with the lowest compression needed the most adjustment to widen a gap enough to get a 0.015 feeler gauge in there. It was about a full counterclockwise rotation of the tappet adjustment screws to get there. From the right side of the engine and having the gas tank and exhaust still in place on the left side, I couldn't get a clear view of the valve movement to see if they were closing all the way. For what it's worth, I couldn't feel any play of the rocker arms when the valves were at bottom of the cam lobe for cylinders 2 and 3. It wasn't like that for cylinders 1 and 2 as there was some clearance.

 

[showcrop]

How does it run under a load?

 

[FarmerBlair]

(quoted from post at 04:52:19 04/11/23)

How does it run under a load?

I haven't actually tried putting a load on it yet. Thought i would run the 5' rototiller on it today and see how it performs. Maybe running hard for a short time will help restore compression... I don't know, just hopeful thinking. Will running it with such a disparity in compression between the inner and outer cylinders going to cause new problems?

 

[FarmerBlair]

So I ran a 5 foot rotary cutter with the tractor to test how it handles that load. The tractor ran surprisingly well. It was also the first time testing the 3pt lift and it held up the mower no problem with no drift down after shutting down the engine. Considering I took the chance and bought this tractor at an auction where no one could start or run the equipment until after the bidding was over, it could have been much worse.
Just have to make time to do a leak test and if need be, take the head off for a valve job.

 

[Eman85]

If it's running OK You might want to run it a little and pull the valve cover and check the valve clearance on the 2 cyls. The sticky valves might loosen up and or there might have been carbon or rust holding them op or keeping them from seating. Then recheck your compression and see what it reads now.