We have a neighbor whose tractor quits running when hot. Tractor has a 5ft brush hog on it. It has already had all the usual things verified as okay. Carb, distributor, coil, gas cap, fuel line, fuel strainer. Someone suggested that the valve adjustments could be too tight, causing loss of compression when the engine gets hot. Tractor starts right up after 10 minute rest. Any ideas? Y'all already know you can't get the valve cover off without removing sheet metal and gas tank.
- Thread starter PopinJohn
- Start date
Stephen Atkins
Member
We had an 850 Ford that would not run when it got hot.(didnt like to be worked hard) Turned out to be vapor lock. The gas line was routed too close to the exhaust manifold. Good tractor.
steveormary
steveormary
It's only a two minute job to take the valve cover off, WITHOUT removing the gas tank and hood. But I don't think you need to go there. If you are SURE of your verified items. than a small gallon of diesel fuel in a full tank of gas will probably solve you "vapor lock' problems. Better double check the ignition switch and/or the coil again.
Vapor lock.
Loose - worn - distributor shaft. Lets the hot vapors get up into the distributor.
Condenser. I've had new ones fail under heat.
Coil. We put a 1 inch wood block behid ours, moved the coil out away from the hot block a bit, thermal insulated it a bit. Helped a lot. Never had one fail, but they didn't like getting as hot as the location Ford placed them.
One or several of those combined will likely cover it.
--->Paul
Loose - worn - distributor shaft. Lets the hot vapors get up into the distributor.
Condenser. I've had new ones fail under heat.
Coil. We put a 1 inch wood block behid ours, moved the coil out away from the hot block a bit, thermal insulated it a bit. Helped a lot. Never had one fail, but they didn't like getting as hot as the location Ford placed them.
One or several of those combined will likely cover it.
--->Paul
Anonymous-0
Well-known Member
Do a compression test when the tractor stalls.
MarkB_MI
Well-known Member
- Location
- Motown USA
"Verified as okay" seems a mite vague to me.
Make sure the points aren't burned and are gapped properly.
Make sure the points aren't burned and are gapped properly.
John:
It's not the valve lash.
Though it probably sounds odd unless you are experienced with vintage Ford tractors, it could be the ignition switch. Replacement Ford ignition switches are well known to develop high resistance after extended periods of use, especially in hot weather. This condition is very difficult to diagnose because the symptoms disappear very quickly after the engine stops if, as is likely, the engine stops with the point contacts open.
Carry a short piece of wire with insulated alligator clips on each end in the toolbox and short out the switch when the engine stops to verify.
Alternatively simply replace the switch with a new one.
Dean
It's not the valve lash.
Though it probably sounds odd unless you are experienced with vintage Ford tractors, it could be the ignition switch. Replacement Ford ignition switches are well known to develop high resistance after extended periods of use, especially in hot weather. This condition is very difficult to diagnose because the symptoms disappear very quickly after the engine stops if, as is likely, the engine stops with the point contacts open.
Carry a short piece of wire with insulated alligator clips on each end in the toolbox and short out the switch when the engine stops to verify.
Alternatively simply replace the switch with a new one.
Dean
David - Alabama
Member
Fuel line to close to exhaust manifold?
I would check the ignition coil primary and secondary windings. If it is even slightly out of limits, replace it. I have seen this several times on other engines from cars / 4-wheelers / outboard motors / chainsaws. Runs good cold, coil starts braking down and delivering weak spark when hot.
As soon as it quits, jump off and check the spark by pulling the center wire out of the distributor cap, holding it near a good ground and trying a start. You should have a FAT, BLUISH-WHITE SPARK, the color of lightning. If you don"t you need to check the coil and and ignition switch, since they cause a sudden shutdown of the engine and after a cool down period, allow a restart.
If the ignition checks out, then check the fuel delivery.
My experience is that when the engine shuts down immediately, it"s generally an ignition problem.
It it misses, cough and sputters and then stops, it"s genrally fuel supply related.
I"ve seen engines overheat due to cooling system problems where they suddenly stop because the piston rings sieze against the cylinder walls but that"s pretty rare.
If the ignition checks out, then check the fuel delivery.
My experience is that when the engine shuts down immediately, it"s generally an ignition problem.
It it misses, cough and sputters and then stops, it"s genrally fuel supply related.
I"ve seen engines overheat due to cooling system problems where they suddenly stop because the piston rings sieze against the cylinder walls but that"s pretty rare.
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