W4 quits when hot

Eric Bergstrom · Jul 4, 2009

After the impressive number of responses given to the gentleman who asked about his Super A, I'd like to see if my problem could be solved as well.

I have a 1949 McCormick W4. It will run well all day long in any gear. However, after plowing or pulling hard for a half hour to an hour, it will eventually start to miss gradually more until it dies. Then, when you go to start it, it turns over a mile a minute, as though the valves are stuck open.

I doubt it's short on gas since it floods instantly when starting (can't find a quality needle and seat anywhere).

We adjusted the valves to .017 and it began to start much easier (it used to be stubborn) but it still acted up. We then adjusted them again, increasing the gaps. Now it starts hard again and still does the same thing when hot.

I can't confirm if it's overheating or not, since the new IH Rochester guage never reads anywhere near "Hot."

I know there are probably plenty of possibilities, but what would you do in this situation?

Andrew Z · Jul 4, 2009

you coil is going dead, when it dies again check for spark at the plugs right away, if its yellow or orange or not there at all then the coil is weak and needs to be replaced.

Andrew

El Toro · Jul 4, 2009

You need to check for fire to your sparkplugs asap when it stops. This needs to be done before it cools. If there's no fire could be a weak coil. If it has a distributor there's been postings on here of the distributor shaft being worn. I would start by replacing the points and condenser. Set the valves at .020" cold. Then run it and see if it will keep running.

You also need to check your gas flow to the carburetor. Remove the gas line at the carb & see if there's a full stream of gas. If that looks ok remove the tube fitting that that your fuel connects to, there may be a screen behind that fitting. Be careful not to damage the fitting. Have you adjusted the main jet adjustment screw near the bottom of of the carb?
Turn it CCW to enrich the fuel mixture. This is used on my garden tractor too to enrich the fuel mixture. Here's a pic of the B&S carb. Hal

Eric Bergstrom · Jul 4, 2009

I forgot to mention that I have a magneto, not a distributor. I know next to nothing about mags as this is the only tractor I've ever had or worked on that has one.

I'll have to set my valves to .020 when cold too.

It would make sense that the spark is weak since it's difficult to start too.

I have a lot to learn. I certainly miss my Grandpa being around to help me with this stuff.

Janicholson · Jul 5, 2009

In addition to the good ideas below, I would add that a compression test just as it quits will tell you if it has a loss of compression causing issues.
Hot engines do crank faster than cold engines, but it might be worth a check. (hold the throttle open while checking) JimN

mkirsch · Jul 5, 2009

Drop the temperature sensor into a bucket of boiling water to see if the gauge works.

El Toro · Jul 5, 2009

If you replace the coil and there's still weak fire from your mag, it may have weak magnets that have lost their magnetism. Hal
PS: I would check them before buying a coil. Touch them with a flatblade screwdriver. Remember this tractor is probably 60 years old and so is the mag. You could convert your mag as shown in this picture using an auto type coil like the Napa IC14SB that has a built-in ballast resistor. Battery voltage would have to be run to the new coil too. That's if your battery is 12 volts for this coil.

W4 quits when hot

Eric Bergstrom

Member

Andrew Z

Well-known Member

El Toro

Well-known Member

Eric Bergstrom

Member

Janicholson

Well-known Member

mkirsch

Well-known Member

El Toro

Well-known Member

Similar threads