Diesel Fuel Cap - Ford 4600

I recently purchased a Ford 4600, a few things were in need of attention.
One of those was the fuel cap. It leaked if the tank was anywhere close to full.
So I visited my local CNH dealer. They sold me a TISCO Cap. E7NN9030AA $5.58
I put it on, filled the tank, no leak. YEA! RIGHT!
Turns out WRONG! Not so fast. Ran tractor for a few hours and had to almost pry the cap off.
When it did release the tank went TONK!, it had been sucked in, lucky for me not hurt.
So I asked the dealer is this right. No cap is to be vented, I'll give you a new one. Checked it first, SAME thing. Bad batch of caps.
I checked caps at Rural King, TSC, another CNH dealer. All the same. Finally checked a dealer out of my area, they had a
CNH cap that is vented. 83961128 $35.81 BUT it works!
I hope this helps someone else.
Keith Williams
 
Pics of fuel caps.
Old - Tisco - CNH

Keith
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One further note. Two times the tractor lost prime at the pump and refused to start. It took a shot of ether to start it up.
I blamed it on me forgetting to release the vacuum on the tank BEFORE I shut down and the tank being lower on fuel ( 6 Gal the one time)
That is why I was GLAD to pay the price of the expensive cap to stop this problem.

At least the cap is what I blamed the no start on. If this theory sounds bogus please let me know. I do NOT like ether.
I hate even worse a tractor that does not start when you ask it to.

BTW: I think this tractor is a girl because the first time it did it was when I was showing it to my girlfriend. I think it was JEALOUS! LOL!

Keith Williams
 
The center one looks -very- similar to the ones I bought at CarQuest for my 7600 and self-propelled mower... no problems with them. Still have one like your old one on my 7000, and one like your new CNH one on my 4600.
 
Word of advise if it applies, I have an old 340 that gets used at the deer lease, leaked fuel around the cap because the tank neck was worn out. Years of fluff, dirt, and diesel stuck all over the tank. Battery tray was also about gone. My friend hit a hole, battery pinched a wire, and it caught fire. I am currently doing what I should've done before, a new battery tray and new fuel tank, plus now I get to rewire and paint... so if you have stuff built up on the tank from your leak, you might want to pull the gauge cluster and clean it all out!
 

Mine have the old cap, I stop filling fuel a inch or two from the top, sometimes the cap gets wet but no noticeable spillage.
The tractors start and run fine so I haven't messed with the caps, MIL's 5600 has a cap like the one on the right.
 

Most modern EMISSIONS era caps have a double valve built in... One for pressure and one for vacuum. SO a little pressure or a little vacuum is tolerated. Too much vacuum and the new plastic tanks will collapse. And a couple pounds of pressure is tolerated.


With that being said... you MUST have a fuel pump to tolerate a bit of vacuum on the tank. Any tractor that has the fuel pump bypassed, cannot use a newer cap.

With so much made in the land of "not so right" I dont know what kind of caps your getting. AND our tractors are all pre-emissions for the most part. I think just a plain "vented" cap is all that is needed and newer pressure-vacuum caps may work ONLY if the fuel pump is still in place. Some of the 30 series and newer have plastic tanks....
 

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