Hot Starting Problems

Tractor starts easily when cold. Won't start when hot. Have ordered new condenser. Anything else to look at? It is getting fuel. Thanks.

Coil

What kind of tractor? When I was a kid, we had an Oliver 70 that if you ever killed it out in the field on a hot day, you may as well have found a shade tree for an hour.

Ignition and carburetion were gone through multiple times, but we never did get it cured. I suspected it was a situation of gas vaporizing from heat in the caburetor. In theory, a gravity feed fuel system shouldn't vapor lock because the weight of the gas in the tank should push vapor through, but it's possible.

I have seen coils and condensers act up when they're hot, but when that happens usually the engine either starts to miss or simply quits while it's running.

If the condenser doesn't fix the problem replace the coil. Hal

How does the hot compression pressure compare to cold compression pressure? We have a tractor that is nearly impossible to start (without towing) when it is hot. It has a brand new magneto, plugs, and wires. It gets fuel and spark, but not enough compression to start easily.

An easy way to see if its an ignition problem is to pull one of the plug wires when its hot and see if there's any fire when cranking. Hal

Electrical connections everywhere get hot, resistance goes up and power goes down.
Large 2/00 electrical cables direct from the battery to the starter solenoid. Direct 2/00 cable from the battery to a bolt on the starter body/frame. 8 or 10 gauge wire from battery to starter switch back to starter solenoid.
The Wallmart 4 and 6 gauge 12V cables are only good for gokarts and lawn tractors.
Make certain the coil polarity is correct. If the battery is + to chassis the coil + goes to the points and the - to the live 12V.
Is the ignition system a bypass design with a 6V coil and ballast resisitor?
What size of battery? A scrawny discount battery isn"t worth beans summer or winter. The only battery to use on any machine is the very highest CCA rated battery that will shoe horn into the battery box.
Note I said CCA not CA rating, much different and designed to fool purchasers.
Another biggy is resistor core ignition wires. Heat affects them too and causes weak spark.
Toss the resisitor wires and plugs as far as possible,install solid core wires and plugs like Autolite 3116,216,473 etc.

It would help if we knew what your working on because on different tractor different things can cause that type of problem. Could be condenser, coil, ignition switch and a good number of other things depending on what it is
Hobby farm

NE Iowa says it right with the fewest words... Coil

Don"t replace anything until you figure out what the root casue of the problem is. When it doesn"t start hot, pull the wire out of the center of the distributor, hold it near a good ground and try to start. You should have a FAT, BLUISH-WHITE SPARK, the color of lightning. If you don"t, then the problem is in the primary ignition ciruit most likely. Some where between the battery, through the key switch, to the coil to the distributor to ground something is not working correctly. Key switches go bad. Jump across the key switch and see if that gives you a spark. If it doesn"t that"s the problem. Crank the engine till the points close and measure the voltage with the key switch on at the battery side of the coil. You should have full battery voltage. Measure the voltage at the distributor side of the coil. It should be near zero with the points closed. Open the points and it should go to battery voltage. if it doesn"t go to battery voltage with points open, then the coil has an open circuit. Do you have the correct coil for your elecrical system. If you have a 12V system, you should have a real 12V coil like NAPA IC-14SB(~$15) or you can use a 6V coil with a current limiting resistor but I would strongly recommend the real 12V coil. One less failure mode!
If you have the requisite, FAT, BLUISH-WHITE SPARK, then check the fuel delivery to the carb. make sure that you don"t have any fuel lines near a hot exhaust manifold where it could cause the fuel to boil and vapor lock. You only have gravity pressure in the fuel systems so if the fuel lines gets hot, it doesn"t take much for the fuel to vaporize in a supply line. Make sure the fuel tank vent is clear. You can check for adequate fuel delivery if your carb has a drain plug in the bottom of the fuel bowl. Open the tank valve and holding a suitable container under it to catch the $4/gallon gas, open the drain plug. The fuels should CONTINUOUSLY GUSH OUT LIKE A COW PEEIN" ON A FLAT ROCK! if it dribbles or is intrmittent, you need to check and see why. Check all the screens and filter between the tank and the carb and look for a kinked fuel line also.
Ifyou systematically make these checks inthe order that I have listed them, you should find the root cause of your problem.

Compression.

Allan

Yepper,

That's a dead giveaway; that hot starting problem.

Can replace coils and condensers all day long until the cows come home. 'Taint gonna helpa bit 'til we have an overhaul.

To test, advance the timing; it should pop off a little easier. BAD COMPRESSION.

Allan

Ive been a mechanic for a long time,and Ive seen 2 coils go bad and neither one stopped it from running,just made it run bad and hard to start hot.I think it was because of rust and the oil leaked out of one.Now maybe coils go bad more for lots of people,maybe theres different coils I never worked with,but coils dont go bad very much as far as I can tell.Also a motor that doesnt have much compression usually smokes quite a bit,maybe even blows oil out the exhaust,and definitely fouls plugs.If your motor is wore out buy a spark plug sandblaster cleaner from Harbor Freight,pull the plugs and blast the crud off of them,blow all the sand off of them with air and it probobly will run.I just started a lawnmower today by cleaning the plug that way.
If your motor is not wore out,then it most likely is a wire connection somewhere,or maybe a slim chance of vapor lock,but thats kind of like that bad coil,I never saw a tractor do that myself and its not likely it will happen with gravity flow.That leaves the condenser,and if that goes bad it usually runs rough first then quits until it cools off.Besides all that it could be lots of things.Best thing to do is like somebody else said right after it wont run see if you have a good spark.If you have good spark,and its wore out real bad it might not have compression.

Farmalls I have seen with mag, condensor in mag was bad. Good start until hot. Then no go.

Farmalls I have seen with mag, condensor in mag was bad. Good start until hot. Then no go.