Ford 8N hard to start when it is hot

[Dave Dowling]

Hi all, I have a 52 Ford 8N with side mount distributor. I've just given the tractor a full tune up including: points, plugs, wires (copper core), condenser, ignition, wire harness,and pertonix flame thrower coil. There has never been a resistor in this tractor so no need to worry about that. Also new rotor and cap and yes the clip is under the rotor. Carb in also new with good gas flow. Just had the manifold off to replace a gasket and static set the distributor with the engine at 4 degree BTDC. It is 6 volts positive ground. The tractor starts right up as long as it is cooled down. But doesn't want to start after running it a while like after brush hogging. It wants to catch but just doesn't fire up. If I turn the key off and turn it back on just before the motor dies she fires right back up, but not if I crank it with the starter. Starter turns over fine and fairly quickly. Also did a dry compression test when engine was cool and got between 95 and 115 PSI, so it seems like the valves and rings seat tight. Exhaust has always been very clean. No black smoke. I've also been running Marvel Mystery Oil in the gas and oil. Any suggestions. Also this is nothing new it has always done this so it wasn't my recent tune up, just listed those items to show you what has been done to eleviate the problem. Thanks!

 

[Bigfoot62]

:welcome:

Well, if you hadn't already changed the coil and condenser, I would have told you to do that first. So, that blows my theory right out of the water!

I'm sure some of the 8N gearheads will be along shortly to figure it out.

 

[GManBart]

I'd put the old condenser and coil back in, and see what happens before doing anything else. If that doesn't work, I'd look at the manifold gasket, to make sure it's sealing when hot.

 

[Bigfoot62]

Bart, he said that,

Also this is nothing new it has always done this so it wasn't my recent tune up

So, I doubt that putting the old parts back on will fix anything.

One more thing, you might try posting in the "Ford Vintage Tractor" section. That might get more attention, especially from the people who could actually help.

 

[Soundguy]

well.. ( deep subject ) lets narrow it to fuel or spark.

we can rule out air and compression. it is getting air or it would not start initially. and dry comp was more than fine.

when hot.. pull the spark plug wire and see if she has spark using a test plug.

if yes.. then pull the air hose tot he carb and give it some ether when starting.. if she starts on that.. you may have a fuel flow issue.

one other thing to try.. hook up your ignition to a battery that is not being used to start, and then start the tractor. IE.. starter is running on a seperate battery than coil.

if it starts.. do voltage drop check ont he starter and starter power wire. if you are dropping past 4.5v it will be harder to start.

post back

 

[Bigfoot62]

well.. ( deep subject ) . . .

if yes.. then pull the air hose tot he carb and give it some ether when starting.. if she starts on that.. you may have a fuel flow issue. . . .

Help me here. Am I dreaming, or was the 8N prone to vapor-lock? If so, a rubber fuel line would probably fix it.

Just thinking out loud. (and it didn't take long! )

 

[Soundguy]

the 8n is a gravity flow system, by definition it cannot have 'vapor lock'.. vapor lock is for fuel pump systems.

however.. runner hoses and scabbed on car fuel filters can cause plenty of problems for the N.

The fuel line on the n is very conducive to gravity flow. out the bottom of the tank over and down to the carb. very easy routing.

 

[Bigfoot62]

the 8n is a gravity flow system, by definition it cannot have 'vapor lock'.. vapor lock is for fuel pump systems. . .

10-4. I've been around the 8N's, but never owned one. Couldn't remember if it was a pressurized system or gravity flow.

 

[Soundguy]

later industrial N engines ( water pumps, gennies.. jeep etc ) DID have the option for a mechanical fuel pump.. but not the ag line...

 

[GManBart]

Bart, he said that,
So, I doubt that putting the old parts back on will fix anything.

Oops....read too fast!