This guide can be used for just about any vintage internal combustion engine.
Even a perfectly-maintained tractor can break. Rarely have I seen a perfectly-maintined tractor. There are certainly none of those lurking around my place. I like to think mine are better than average, but when other projects jump to the top of the list, maintenance takes a back seat.
Cold Weather Starting - When the temperature drops below freezing, do your tractor a favor, and slap a magnetic heater on the oil pan about 30 minutes before trying to start it. Grinding the starter until it finally catches is bad. An even worse habit is giving it a shot of starter fluid.
When we fall behind on maintenance, more and more little problems begin to add up. Any no-start conditon usually has more than one cause. This is certainly the case when a tractor that has been getting harder to start for several months suddenly becomes a no-start. Every time I go thru a no-start condition with someone, we end up fixing several problems. Funny, it's always the last thing we fix that gets blamed for being "the" problem.
These engines are really very simple. An engineering degree is not required. They only need three things to run: COMPRESSION, FUEL, and SPARK (at the correct time). The engine should fire right up unless flooded. When that happens, I can smell it, and I know exactly what I did to cause the problem. Too much choke is a very common problem with these engines. They are very easy to flood. Let go of the choke knob, open the throttle, and see if it will fire, and clear the plugs. If you are using Autolite 437 plugs, it should clean up and start running right. If you are using any other plug, it may not even fire unless you put in a clean, dry set of plugs.
If you are attempting to bring a tractor back from the dead, and the engine has been sitting for months, or years, please follow this link to a list of steps that must be taken to prevent severe damage. DRY ENGINE
Before we get into step-by-step trouble shooting, it's important to have a dasic understanding of how the engine works.
Hopefully the compression check is good, because without that we are done before we start. Even without a genuine compression gauge, we can get a good idea that an engine has decent compression just by trying to turn it by hand. Grab the fan belt and pull. The engine should turn fairly easy until one of the pistons starts to move up with the valves closed. Even better, just pay attention to how the engine cranks with the plugs out, then with the plugs in. Big difference = Good. Little Difference = Bad.
The engine compression checks are the best way to discover major engine problems, and get an idea of overall engine condition. If the compression is very low, all the things we might do to try and get the engine to run are a complete waste of time. All compression checks are done with all the spark plugs removed and a fully-charged battery. Zero the compression gauge and put it on one spark plug hole. Crank the engine over with the starter. The cylinder you are checking should go through 3 or 4 compression cycles. The compression gauge will remain on the highest value. Write that down, zero the gauge, and do the next cylinder. Once you have the dry numbers for each cylinder, pour a little motor oil in each cylinder. Crank the engine a few times to circulate the oil. Do the compression check again for each cylinder and write down these "wet" numbers.
What we are looking for is "dry" compresion numbers of at least 90 PSI. "Wet" compression values that are much higher than the dry numbers indicates worn and scratched cylinders, possibly broken rings. If this engine was frozen and just broken loose, that may have snapped a ring or two. One or two cylinders with dry and wet compression much lower than other cylinders can be caused by stuck or burned valves, blown head gasket, or cracked head. Stuck valves can be un-stuck by removing the valve covers. Look for valves that don't follow the lifter back down. There's the problem. Soaking in ATF, and maybe a little PB Blaster may help unstick them by hand. Valves may need to be unstuck a few times before the solvent takes care of the problem.
If the tractor has been converted to 12 volts, it will crank faster, and the compression will be higher. This can allow an old tired engine to continue in service longer. A worn out engine will only continue to have less power, and be harder to start. My tips on engine rebuilding can be found here Engine Rebuilding.
Fuel needs to travel from the fuel tank, down the fuel line to the carburetor, where it will be vaporized and drawn into the cylinders of the engine through the manifold and intake valves. Ok, that might be getting a bit too technical.
Start with the simple stuff. Is there fuel in the fuel tank? Is the fuel more than a year old? Is the tank reasonably clean, or full of trash and sludge? Is the tank vent open? Is the fuel shutoff valve open? Are the fuel screens clean? Is the fuel line reasonably straight and not kinked? Is the carburetor bowl filling with fuel?
That may seem like a lot to check, but one simple test will verify if all that "stuff" is ok. Find a clean can (about a quart size, with a large opening). Remove the bolt from the bottom of the carb. This is the carb drain plug. Fuel will come out. Open the fuel valve two full turns, and watch the fuel flow. There should be a steady stream of fuel. If not, the fun begins. Servicing the fuel system is just taking apart and cleaning everything from the tank to the carb. Please refer to my complete Fuel System tune up page - Click Here.
The Spark or Ignition System is easily checked by simply pulling a plug wire loose from the spark plug, and holding the metal end about 1/4" away from the metal engine block. Don't worry about paint. The high voltage spark will jump right through the paint to the metal. What we like to see is a nice Crackling-Blue spark that will easily jump 1/4" or more. If you see nothing, or a weak-whimpy yellow spark, we have ignition problems. Please refer to my complete Ignition System tune up page - Click Here.
By the time I start trying to get one of these tractors running, it usually has a bunch of brand new parts. It is much better to find and fix whatever is causing hard-to-start condition before it becomes a no-start, with a dead battery, fried starter, welded solenoid, dirty air filter, ancient plugs, cracked distributor, rotten wiring, clogged fuel screens, etc......................
Let's assume your tractor has been running ok and suddenly just won't start. These will be listed with the easiest and least expensive items first. There is no point in replacing a $30 coil at Step 1, unless we are certain we need a new coil. If the engine won't even crank, Click Here.
Did you forget to turn the ignition key on? These engines crank when the start button is pressed, even with the ignition turned off. Go ahead and laugh, I've flooded mine many times, cranking with the key off. It got so bad I added an ignition ON light to the dash of all my tractors. Problem Solved.
Water in Distributor - Does this no-start happen when the tractor get's wet. Rain, dew, or melting snow could be getting inside the distributor. Remove cap, dry out any signs of moisture. On a front distributor engine, check the gaskets and replace if necessary.
Points are usually the first thing I check when one of mine won't start. The points move more than anything else, and moving parts is where problems occur most frequently. Keep a point file handy, check the point gap. If this is a front distributor engine, take two minutes, remove the distributor, and take it inside where you can get comfortable. Specific distributor tune up info can be found Here
Check Ignition Circuit - Use a voltmeter to check votage at battery, both sides of key switch, resistor, coil and distributor. Verify correct connections to points, and condenser. If this circuit is grounded or open at any point it will not work. Especially look at any flexible copper strips to the points. Other problem areas are where the coil wire passes through the side distributor body, and the front distributor coiled springy terminal connection to the points. Try "hot-wiring" the tractor with a wire directly from the ungrounded battery terminal to the coil. If it starts that way, the problem is somewhere in the ignition circuit. Jumper individual parts and wiring to find the problem.
Don't start fiddling with the carb! The Carb is almost always the LEAST LIKELY source of trouble.
One of the first hard lessons I learned is that almost EVERYBODY starts start out fiddling with the carb when they are looking for a problem. But 99 percent of the time, the problem is somewhere else. All we are doing is CREATING more problems by fiddling with the carb.
Think about it a second. What are the chances that the carb has all of a sudden become misadjusted? All those little spring-loaded adjusting screws just started re-adjusting themselves, right? We often use those adjustments to make our engine run better, because it is easier to turn an adjusting screw than anything else. These adjustments can compensate for and mask other problems, but when we are eventually forced to find and fix the real problem, we will now have to readjust the carb. This is at least twice as much work as staying on top of the regular maintenance. Always start by looking for and fixing the most likely problems like fuel supply, clogged filters, corroded connections, burnt points, fouled plugs, etc.
If you smell gas, and it won't fire, remove the spark plugs, and replace with a fresh set. If they are fairly new, and just wet, you can dry them with a propane torch. Just cook off the moisture, and check the gap, we are not trying to melt them down.
Try stepping on the clutch, even with the transmission in neutral, stepping on the clutch removes a lot of rotating parts, so the engine should turn over a little easier.
Bad Gas - Look at the fuel in the glass fuel bowl. Do you see dirt, or anything that looks like water bubbles? If the tank is less than half full, but looks clean, fill the tank with fresh fuel, then drain-off a little through the carb. Close the fuel valve, remove and clean the glass bowl. Clean or replace fuel screens. Water in the fuel could just be from condensation. Drain the tank and fill with fresh fuel.
These tractors will tell us when something is going bad. If your tractor starts, but still has problems, here are the most common symptoms and solutions.
Runs for about 1-minute and quits; restarts in about 5-minutes = BAD CONDENSER, replace it.
Runs for about 3-minutes and quits; will not restart = GAS TURNED OFF (go ahead and laugh, I've done it, more than once).
Runs for about 5-minutes and quits; restarts in about 10-minutes = CLOGGED FUEL SCREEN. Fuel trickles but won't flow.
Runs for about 15-minutes and quits; restarts after about 30-minutes cooldown = BAD IGNITION SWITCH. Install jumper around switch and start engine to test. If problem goes away, replace ignition switch. Do not leave that jumper connected, or ignition key ON, with the engine stopped = Fried Points and Coil.
Runs for about 30-minutes and quits or starts running rough; but after 1-hour cool down, engine restarts and runs fine = BAD IGNITION COIL, replace ignition coil.
Tractor is flooded, gas leaking out of carb. Float valve in carb may be stuck (whack side of carb with a wooden hammer or screwdriver handle). A carb rebuld may be needed if this isn't a one-time thing.
Leaking or cracked manifold, Bad or Broken plug wires, Incorrect firing order (should be 1243 front to back).
An engine that has been getting harder to start may have a dirty carb. If your carb looks like this one:
I keep a couple rebuilt carbs around. Swapping carbs only takes 30 minutes or so. That's a lot less time than doing a rebuild when I need the tractor for something.
A fresh carb solved the problem. Sometimes it is the carb. Could the old carb have been adjusted? Maybe, but I've found any clean carb starts and runs much better than a dirty one. The 8N is back to starting almost as soon as I touch the button.
Since I recently rebuilt the dirty carb, I know all it needs is a good cleaning and gaskets. No need to fork out cash for a rebuild kit.
BACK TO TOPContent and Web Design by K. LaRue — This Site Was Last Updated 16 AUG 2018.
Optimized for Firefox
All Tradenames and Trademarks referred to on these web pages are the property of their respective trademark holders. None of these trademark holders are affiliated with this web site, nor is this site sponsored or endorsed by them in any way.
All email addresses for this web site are set to agressively block ALL unsolicited advertising, sales pitches, nuisance web service offers, and other spam messages. I do not, and will not respond to the few that manage to make it thru the filters.