601 quits running when warm

bluthum

New User
New member here and in need of advice. I've got a 601 ford that I've used moderately for about 20 years. Ol' Bob is important to have around my homestead.

Anyway the 601 has always had the problem of conking out when it gets warm enough. If the weather out is 90 or so it will run about 45 minutes and quit. You can choke it back to life but it runs ragged and you have to manipulate the choke. Problem is rare in the winter. Cooling system seems fine and the temp gauge is working.

I'd always thought it was the coil but with a new heavy duty coil it does the same thing. The ignition is still contact points and it does not have a primary resister. A new set of points will start to burn out after about 50 hours which I can live with but any way points and condenser have been frequently changed.

I bought an electronic ignition kit for it but have never installed it, I hate fiddling with those little screws.

Any way any ideas why this is happening would be gratefully considered. Thanks in advance!
 
A few weeks ago there was a similar discussion. Your fuel line may be to close to the exhaust manifold vapor locking it and your fuel tank should have that nice big metal shield under it over the muffler.
Also, maybe the screen is getting clogged inside the fuel tank after sloshing around for awhile. Not impossible.
 
Ignition switch? Try bypassing it when it starts to act up.
Fuel delivery? Can you fill a pint jar in two minutes from the drain plug at the bottom of the carburetor when it starts to act up.
Vacuum leak? Try spaying starting fluid around the carburetor mounting and all over the intake manifold when it starts to act up.
Just some thoughts,
 
The heat shield is in place and good shape. Since I got over the coil failure theory I'm sure thinking it's a fuel thing as you mentioned.

For some reason I'd gotten the impression over the years that vapor lock was a myth but then again here we are with gravity flow delivery It could be the fuel screen in the tank but I've replaced the valve assembly and ancient tank crud was minimal. Also today I emptied the sediment bowl and there wasn't much there either.

I'm making notes here for when I get ready to heat it up and really analyze the issue instead of just walking back to the house.

Thank you very much for the insights.
 
More good suggestions. The fuel delivery test seems to be at the top of the diagnosis list. Could you unscrew the sediment bowl and reliably measure from there rather than the carb? I'm not certain the Zenith carb has a bottom drain but I'll check.

Ignition switch seems like a wild card but if I knew I'd not be here asking. Will check.

Also I hadn't considered the possibility of a vacuum leak. Drat! A whole 'nother world.

I long ago got over finding satisfaction in working on anything that burns gas but it goes with the turf. I dearly love using the ancient tractor to help with the chores and the only thing harder than finding some one to work on these old units is paying for it.

Thanks for the input, this site rocks...
 
Could you unscrew the sediment bowl and reliably measure from there rather than the carb?

Only if you're absolutely certain that there's no obstruction between the sediment bowl and the bowl of the carb, including the needle valve not being stuck.
 
Yes it sounds like vapor lock. I had a Case 351 tractor with side shields and a downdraft muffler. You couldn't keep the shields on in hot weather. Also the ignition
switch. I had that problem on another Case. It would start but then quit. The wire to the dash switch was a little loose. Not sure why it ever started but it would
start and die after a while. Tightening the wire fixed the problem.
 
First off you need to be positive about
whether it's an electrical or a fuel
issue. The easy way to do that is to put
a timing light on it and tape or strap
it somewhere you can watch the flash.
Then go to work. If the light stays
consistent when it starts giving trouble
it's a fuel issue. If the light stops
the flashing pattern it's electrical.

If it's fuel I would replace the vented
gas tank cap first. If that doesn't work
re route the fuel line as has been
mentioned often here.
 
Agreed.

Could well be the not uncommon Ford tractor ignition switch gremlin which is difficult to diagnose, especially in a chat forum.

Short out the ignition switch the next time that you use it in hot weather to see what happens. No change, not the ignition switch. Problem solved, replace switch.

Dean
 
(quoted from post at 07:44:15 09/05/21) Agreed.

Could well be the not uncommon Ford tractor ignition switch gremlin which is difficult to diagnose, especially in a chat forum.

Short out the ignition switch the next time that you use it in hot weather to see what happens. No change, not the ignition switch. Problem solved, replace switch.

Dean

I'm still puzzling over the nuts and bolts of how this site works but the info posted by members has been outstanding. Thanks some more to all, I've not had a chance to put all the suggestions is into play yet.
 
I have a 650 doing the same problem. I have changed the points to the electronic ignition and it still runs for about 45 mins and quits. Can someone explain the vapor lock?
 

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