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Farmall & IHC Tractors Discussion Forum

Starting my 300U

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05-05-2014 22:10:45

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I'm having a heck of a time getting my 300u to fire up. I replaced the head gasket after finding water in the oil, and did serious clean-up, but not a rebuild, on the carb.

I've checked all the plugs with a spark tester, as well as outside the cylinder. The coil is brand new, from NAPA. I did a compression test and all 4 cylinders have good compression. First stroke hits 90 psi, which is 6.6 x 13.6. It tops at 120 psi, which I assume is okay.

That left me fuel and timing. The plugs are getting wetted with gas, so I'm pretty sure I'm getting fuel. I even tried a spray can of stating fluid, which I can reliably ignite in the carb by setting timing back far enough, but not in the cylinder.
No matter where I set the timing, I cannot get this thing to fire. Is there something else I'm missing? Spark heat? I've already burned up an old battery trying to start it.

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05-07-2014 12:51:21

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 Re: Starting my 300U in reply to Danby, 05-05-2014 22:10:45  
I'd like to thank everybody that provided suggestions, Wayne especially. Following his instructions led to the discovery that I had offset the plug wires by 1 so that wire #1 was at wire #4's post on the distributor, etc. That's fixed and now I can reliably backfire.

Seems the choke pivot pin is loose and will the choke will close itself with vibration. Also, I appear to be flooding, or maybe the backfire splashed gas into the lower part of the carb.
Either way, I'm pulling the carb tomorrow and fixing it.

Also, the rotor seems a bit loose to me. I'm used to a little wobble, but I can wiggle it some 30 degrees or so. Is that normal? It seems too much for gear lash. Or am I just working the vacuum advance?

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wayne in mn

05-06-2014 11:07:25

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 Re: Starting my 300U in reply to Danby, 05-05-2014 22:10:45  
First, accurately locate TDC for #1 cylinder on compression stroke, the points should JUST BEGIN to open at that point. If not, follow the procedure below to set spark timing.
Use an ohmmeter with a low reading setting and attach one lead to the points wire going into the distributor body and the other meter wire to the metal side of the distributor body. (I prefer to remove the cap, rotor, & protective cover over the points so I can see what is going on) Replace the rotor temporarily for reference purposes.
Loosen the distributor hold-down capscrews so you can just rotate the distributor body. Rotate the distributor body CCW (looking from the operator seated position) until the points rubbing block is on the cam lobe highest part. Point gap is .020”. Adjust as needed.
Rotate the distributor body clockwise until the ohmmeter shows that the points are closed. If you cannot get a 0 or nearly 0 reading then clean the contacts with a very fine abrasive and spray some contact cleaner or brake cleaner (no carb cleaner, it leaves residue) and snap the movable point arm with your finger verifying a good, clean connection. You may need to remove the points and clean underneath them. The meter should read infinity with the points open.
Since you previously found TDC #1 cylinder now slowly rotate the distributor body slowly CCW until the meter just begins to indicate the points are opening.
Tighten the hold-down capscrews, replace the points cover & rotor, distributor cap (the rotor should point to #1 tower in the cap), verify the firing order (1-3-2-4 in the CW direction), and you should be good to go.
IF the cap is not cracked, IF the rotor is not carbon tracked, IF the wires are in good condition, IF the sparkplugs are good, all should be well.
I like to remove the coil-to-cap wire at the cap and use a jump gap tester to make sure there is decent spark. (1/4” bright blue and snappy).
Happy “sparking”.

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05-06-2014 08:55:44

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 Re: Starting my 300U in reply to Danby, 05-05-2014 22:10:45  
As soon as you said coil from Srappa that is your problem. The coil has a resistor block on it? You MUST have that block. Drops the 12volts down to an 8volt coil. Most all car coils are like this. The problem is when you crank you do not have enough voltage at the coil to fire. Run a tiny wire from the output side of the solinoid to the + side of the coil. You will need to be able to remove this wire as SOON as the tractor fires up. If she fires right up you found the trouble. Install a Diode in this little wire and from now on it should work and not try to feed voltage back to the starter. Have seen this on a couple of 6 to 12 volt conversions that were not done correctly.

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05-06-2014 07:28:19

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 Re: Starting my 300U in reply to Danby, 05-05-2014 22:10:45  
Do you actually have spark?

Check for power at the coil. Should have near battery voltage at input to coil. Wire from coil to distributor should have near battery voltage with points open and zero volts with points closed.

Remove center wire from distributor and set it close to engine block. When you crank engine with switch on a strong spark should jump a quarter inch gap.

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used red mn

05-06-2014 05:09:27

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 Re: Starting my 300U in reply to Danby, 05-05-2014 22:10:45  
Not knowing your skill level with engines I would have to ask if you are sure your distributor is timed to fire #1 spark plug at TDC of its compression stroke? You do know that just aligning the timing mark on the crank pulley may also be setting your engine at TDC of the exhaust stroke.

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05-06-2014 03:08:22

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 Re: Starting my 300U in reply to Danby, 05-05-2014 22:10:45  
Are the spark plugs brand new and are they set to the right gap? If so, try setting it at TDC and then tow it with another tractor or a truck. That has always worked for me.

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