spark jumping outside plugs

Got a 4 cyl ford 2000 tractor that is having issues after running for an hour or so. Couple weeks back it started missing and cutting out and I saw and heard arcing outside the plugs. I parked it and just got back to it.

Put new ngk B-4L spark plugs in there and all seemed good for a little while then same problem. Pulled the cap and rotor, checked point gap, cleaned all metal arcing surfaces on cap and rotor, checked resistance on all solid copper core wires, applied dielectric grease in boots over cap and plugs and checked resistance on plugs. Everything looked great, almost no resistance on plugs or wires and nothing had any corrosion.

Took it out and mowed for an hour or two in the hot sun and smelled gas. I had put a sealed gas cap on it at one point and it was leaking because it was under a ton of pressure. Safely got the gas cap off and the fuel was boiling. Need to get non ethanol fuel, fab an exhaust heat shield and the proper gas cap.

After letting it cool just long enough for the fuel to stop boiling I drove it back up to the house and on the way up it was cutting out again. Once I parked it I looked and all 4 spark plugs were arcing along the plug from under the boot to the base of the plug.

The temp gauge is showing normal holding @ 160 and I've never messed with the carb but the plugs I pulled looked good so I don't suspect a problem there not do I know how either of those could cause this.

Anyone have any ideas on what could cause this?

Carbon tracked plug boots

Yup, deteriorated boots. Do you have the heat shield that goes above the muffler in place?

Shouldn't that tractor have a vented gas cap?

Wires are less than a year old but I bought a set of 6 cause it was the same price as the 4 pack so I've got two spares to try. I just didn't think about that because they work fine for a while then all the sudden all of them start doing it.

No heat shield in place. I see holes on the bottom of the tank bracket where one would go so I will fab something up.

And the vented cap would leak all over while moving so I put an automotive cap on. Just put the old one back on for now but man if my tank is more than half full gas goes everywhere.

So I'll fab a heat shield, keep my tank low, and try 2 new wires and report back after I get to use it again.

(quoted from post at 18:45:24 07/17/21) Wires are less than a year old but I bought a set of 6 cause it was the same price as the 4 pack so I've got two spares to try. I just didn't think about that because they work fine for a while then all the sudden all of them start doing it.

No heat shield in place. I see holes on the bottom of the tank bracket where one would go so I will fab something up.

And the vented cap would leak all over while moving so I put an automotive cap on. Just put the old one back on for now but man if my tank is more than half full gas goes everywhere.

So I'll fab a heat shield, keep my tank low, and try 2 new wires and report back after I get to use it again.

Click to expand...

From the on line parts book it looks like Ford had an improved cap for yours and some others. Here's one on eBay.

https://www.ebay.com/itm/184630738034

(quoted from post at 15:45:24 07/17/21) Wires are less than a year old but I bought a set of 6 cause it was the same price as the 4 pack so I've got two spares to try. I just didn't think about that because they work fine for a while then all the sudden all of them start doing it.

No heat shield in place. I see holes on the bottom of the tank bracket where one would go so I will fab something up.

And the vented cap would leak all over while moving so I put an automotive cap on. Just put the old one back on for now but man if my tank is more than half full gas goes everywhere.

So I'll fab a heat shield, keep my tank low, and try 2 new wires and report back after I get to use it again.

Click to expand...

If your vented cap leaks you need a new one. They were not designed or sold to leak.

Ok got some work done today with no answers on the spark issue. I put 2 new wires on there with dielectric grease of course and still the same problem.

I just don't get it. With no resistance in the wires, non resistor plugs, and a .025" gap ath the end of the plug why would the spark instead jump a 1" gap to arc outside the plug. It also arcs sometimes from the boot on the cap over to a power steering line. It hasn't ever done this until it started a little while back. Also this time it started doing it immediately instead of running fine for an hour before hand.

On a positive note I found a piece of stainless and made a heat shield today. If I can figure out how to post pictures I'll upload a few.

I would hope they weren't meant to leak. I almost bought the gas cap you linked and decided to look at clearance and that cap won't fit. The cap that's on there now extends about 3/8" over the neck and I've only got about a 1/4" clearance above the cap to the hood. It has to be a short cap like what's on there.[/img:21e065e7da]

Tried to post pics but it said something about inappropriate words although there were only the images in the post. I think it's something to do with being a new account but can't find info in the FAQs about post count for images. Oh well.

(quoted from post at 17:01:38 07/19/21) Ok got some work done today with no answers on the spark issue. I put 2 new wires on there with dielectric grease of course and still the same problem.

I just don't get it. With no resistance in the wires, non resistor plugs, and a .025" gap ath the end of the plug why would the spark instead jump a 1" gap to arc outside the plug. It also arcs sometimes from the boot on the cap over to a power steering line. It hasn't ever done this until it started a little while back. Also this time it started doing it immediately instead of running fine for an hour before hand.

On a positive note I found a piece of stainless and made a heat shield today. If I can figure out how to post pictures I'll upload a few.

I would hope they weren't meant to leak. I almost bought the gas cap you linked and decided to look at clearance and that cap won't fit. The cap that's on there now extends about 3/8" over the neck and I've only got about a 1/4" clearance above the cap to the hood. It has to be a short cap like what's on there.[/img:168b3805b3]

Click to expand...

The correct caps on my tanks extend only about 1/4" above the neck