MF65 turns over but wont fire

[HoosierMuscle]

I'm new to the old tractor world and glad I found this page. Thanks in advance!

1965 MF 65 with 4 cylinder gas engine. Story behind this tractor is it has sat in a barn for about the last 8 years and I don't know its status or history before getting in there. I have done the following so far: New battery, rebuild carburetor, new coil, new distributor cap/rotor/points, cleaned gas tank and new fuel bowl. I put some fresh gas in it and it fired up immediately but then died within seconds. After that, I could never get more than a second or 2 of it firing. At this point, I can't even get it to fire even with starting fluid. I have checked and I have spark on all cylinders. I checked and have compression on cylinders: 100, 116, 120, & 119. I'm not sure distributor layout but read that 1 is closest to front of tractor and then it is 3, 4, & 2 going counter clockwise from there. Cylinder 1, 2, 3, 4 are from the front to back. My next step was to put new spark plugs on it to try and then maybe pull the carb again to see if I screwed something up on the rebuild. Any other ideas? Thanks!

Update: Right before getting dark, I noticed the exhaust manifold was cracked. I see that the intake and exhaust are a 1 piece. Wondering if my intake is cracked and thus not pulling fuel into engine. Anyone had this experience?

This post was edited by HoosierMuscle on 04/26/2023 at 02:17 am.

 

[RM-MN]

An engine needs a few things to be able to run. Fuel mixed with air (carburetor function) compressed in the cylinders, then ignited by some means such as spark.
You have rebuilt the carburetor so the fuel-air mix is probably close enough and the fact that it started once confirms that. You mentioned that you have spark on all cylinders but how good is it? Is it capable of jumping a quarter inch gap with a bright blue/white spark? Do you have a good supply of fuel? There should be a drain on the bottom of the carburetor. Open that and catch the fuel that comes out. At first there should be a fast flow as the fuel in the carburetor drains. The it should have a slower flow as the inlet valve (float valve) opens and that should continue as a continuous flow. I would probably suspect lack of fuel as the cause of it not continuing to run as it started once.

 

[wjytexas]

If your fuel flow is slow check this next. Most sediment bowls are designed to be opened 3 full turns for normal operation and all the way to access the reserve in the bottom of the tank. If you put less than 3 or 4 gallons in the tank try opening the valve all the way.

 

[da.bees]

Fish the old parts out of trash and reinstall old condenser. If there's no improvement reinstall old coil. The out of the box failure is about 25% for condensers and another 10% fail within a few hours running. Coils not near as bad but some still fail early. Before tearing into carb I'd drain carb to prevent flooding then see if it will hit on starting fluid.

 

[jt501]

is the neutral safety switch still hooked up and operational on your tractor?

 

[used red MN]

Hello Hoosier welcome to YT! RM-MN has a very good layout of what you need to do as I agree it is most likely a fuel problem. The suggestion to give it a squirt or two of starting fluid to see if it runs on that is also a good way to prove if the ignition is working or not. Even just pulling a couple spark plugs and dumping a couple tablespoons of gas in each and then cranking it will confirm if the ignition is working. Look at the carb diagram in the link. Just make sure number 12 the venturi was reinstalled when the carb was assembled. If this is not in there the carb cannot draw fuel out of the main nozzle number 24. RMs method of checking gas flow from the carb bowl drain will confirm if the following is a problem or not. Not sure if either of the carbs that this tractor used has one, but many old tractors do. I am talking about a fine screen on the fitting that the fuel line connects to carb by. This type of screen can plug and stop fuel from getting in the carb even though you may have confirmed good flow from the line itself.
Carb diagram

 

[HoosierMuscle]

Thanks all for the comments. Tomorrow should be rain free so I'll try putting some gas directly in through spark plug holes and give that a try. I haven't had any luck with starting fluid which made me think I'm not pulling vacuum to pull fuel in. That made me start questioning if the intake had a crack. It if fires when I put fuel directly in cylinders, I'll pull the carb and see what is going on there.

 

[HoosierMuscle]

I used a turkey baster to put some gasoline directly into each cylinder, then quickly reinstall the plugs. It still would not fire. I put the old condenser back in. Still not firing. I pulled each spark plug out and keep them on the wire to check for spark. I have spark on each plug. I'm wondering if the spark is just weak. I have a new coil on there along with new distributor cap, rotor, and points. Spark plugs and wires are old. I'm thinking next step is plugs and wires. Thoughts?

 

[Jim.ME]

Check the basic timing. Going by a picture or where a book says #1 should be in the distributor cap does not mean that is correct for your engine.

Pull the plugs out so the engine turns easy. Put a cotton ball, or wad of paper towel, lightly in the #1 plug hole to seal it. Turn the engine over in the correct rotation until the cotton ball pops out. At the point #1 is coming up on compression ready to fire. Continue to turn the engine to line up the timing marks. At this point the rotor should be pointing at the plug terminal in the distributor cap where the #1 wire should be. Check and report what you find.

This post was edited by Jim.ME on 05/05/2023 at 02:49 pm.

 

[HoosierMuscle]

(quoted from post at 17:30:02 04/30/23)
Check the basic timing. Going by a picture or where a book says #1 should be in the distributor cap does not mean that is correct for your engine.

Pull the plugs out so the engine turns easy. Put a cotton ball, or was of paper towel, lightly in the #1 plug hole to seal it. Turn the engine over in the correct rotation until the cotton ball pops out. At the point #1 is coming up on compression ready to fire. Continue to turn the engine to line up the timing marks. At this point the rotor should be pointing at the plug terminal in the distributor cap where the #1 wire should be. Check and report what you find.

I can actually see through the spark plug hole and see when the piston is up top. In the attached photo I marked everything. Getting ready to be on vacation for a while so will get back to it later.

 

[Jim.ME]

Just because you can see the piston at the top does not mean it is on the compression stroke, any more than looking at the timing mark and seeing it is at the TDC mark means it is properly timed. A four-stroke engine is only on the correct stroke to fire every other 360-degree rotation. The pistons are at the top when on the compression stroke, where it should fire. They are also at the top on the next 360 revolution of the engine at the top of the exhaust stroke, where it should not be firing. The distributor turns at 1/2 engine speed to allow for this. That is why I suggested you use a cotton ball to find the compression stroke of #1 cylinder (using a finger over the hole is another way to feel the compression or put a compression gauge in the #1 hole). The other option to confirm the correct stroke is to remove the valve cover and see if both valves are closed (rockers should have play between them and the valve stems) on #1 cylinder and the #4 cylinder valves are on the rock (exhaust valve is just closing at the end of its exhaust stroke and the intake valve is just opening to allow air and fuel in during the intake stroke), there should be no play between the #4 valves stems and rockers. If you did not verify by compression or valve position, you may well be 180 degrees out on timing.

 

[Jim.ME]

And if #1 is in proper position in your picture, the firing order for the plug wires in the distributor cap would be in the positions shown below for a distributor rotating counter clockwise.. They would always be in the same location related to #1 even if #1 is in a different cap terminal location. They do not go 1, 2, 3, 4 around the cap.

 

[HoosierMuscle]

You sir, are my favorite person today. Here is what I ended up with. It will fire and run for a few seconds then dies. I m thinking it s running out of fuel and need to do some carb work.

 

[HoosierMuscle]

A little carb adjustment and it runs! Thanks for all the help!

 

[Jim.ME]

Now check the timing with a timing light which will also show you if the advance in the distributor is working. Your manual should give you the base timing at idle and full advance timing at high idle.