Fuel tank breather

This forum is for the Fordson New Major, including the Super Major and the Power Major.
Post Reply
smchris
True Blue
Posts: 78
Joined: Mon May 03, 2021 9:39 am

Fuel tank breather

Post by smchris »

Hi everyone,

I've found that the tank cap on my Super has been painted over at some point, blocking the breather hole that must have been there. After it's been running for a while, the tank builds a vacuum. I noticed this when looking at the lift pump sight glass, which showed a stream of tiny bubbles being pulled in. The absence of a leak normally suggested this was low pressure within the fuel system below atmospheric. Sure enough, remove the tank cap and it goes "suck" and the bubble stream vanishes.

Someone seems to have applied paint across the cap top at some point. I presume there was a breather inlet there somewhere, but not having seen an unmutilated tank cap, I've no idea where it should be to locate it and re-open it.

Can anyone send me a pic of what the cap should look like and where the breather hole is in the cap please?

Cheers

Chris

Billy26F5
True Blue
Posts: 1912
Joined: Fri Jun 26, 2020 12:01 am
Location: On Billy

Re: Fuel tank breather

Post by Billy26F5 »

Can you post a pic of your cap? We have both original caps but I don't have a pic right now, I'll post them tomorrow. There's no hole outside, you might need to unblock the internal valve (if you have one). Bubbles mean you need to inspect both olives, the lift pump diphragm and the fuel tap o-ring for leaks, if all of those are fine the leak will probably be more difficult to find; try to leave all the parts clean and leave them for a bit, then come back and see where there's diesel on the bits you cleaned, then check how tight the connections are, loose connections will leak.
Sandy
ImageImageImage

smchris
True Blue
Posts: 78
Joined: Mon May 03, 2021 9:39 am

Re: Fuel tank breather

Post by smchris »

Thanks Sandy.

In my post I point out that I only get a stream of tiny bubbles up the side of the sight glass when the tank builds a vacuum after a period of running. This is to be expected because the fuel system ends up under negative pressure because as the tank empties it leaves behind a void that cannot be replaced by ambient pressure air. When the vacuum vents (by removing and replacing the cap) the bubble stream ceases. There is no leak under normal circumstances, so I'm not worried about that. It's clear that there is a blocked breather somewhere.

However, I have no idea where any other tank breathers are; logically, the usual site is in the cap. I suspect the injudicious paint job.

It could be - normally - through the rivet that holds the tank sealing rubber in place. A negative pressure in the tank could pull the centre down and admit air. But because I've not seen an unpainted cap, I don't know of this is the case...

Billy26F5
True Blue
Posts: 1912
Joined: Fri Jun 26, 2020 12:01 am
Location: On Billy

Re: Fuel tank breather

Post by Billy26F5 »

The rivet is sealed, if with that vacuum you have bubbles it indicates a leak, a good connection can cause the tank to implode as indicated by Brian years ago (or so I remember! please correct me if I'm wrong on this). If you can post a pic of the cap it might show it's not a fuel cap, I will post pics of both fuel caps tomorrow.
Sandy
ImageImageImage

Billy26F5
True Blue
Posts: 1912
Joined: Fri Jun 26, 2020 12:01 am
Location: On Billy

Re: Fuel tank breather

Post by Billy26F5 »

Here are the pics.
This is the early cap (Billy's one), used on early Major's,
Image
Image
this one (Davie's one) is the late one, you can see the valve in the centre.
Image
Image
And just in case, here's the Ebro version of the second cap, as used by Super Billy.
Image
Image
Sandy
ImageImageImage

smchris
True Blue
Posts: 78
Joined: Mon May 03, 2021 9:39 am

Re: Fuel tank breather

Post by smchris »

Thanks. I'll take some shots next time I'm in the barn and you can inspect!

I'm dubious that mine isn't like any of those and might therefore be a misfit, and that's the reason we've got this issue....

C

John b
True Blue
Posts: 537
Joined: Tue May 19, 2020 8:40 pm

Re: Fuel tank breather

Post by John b »

New fuel caps are quite cheap but i have a spare AC cap if you want to keep your tractor original, it's not mint but not in bad condition
John
My biggest fear is that when i die my wife will sell my tractors for what i told her they cost

smchris
True Blue
Posts: 78
Joined: Mon May 03, 2021 9:39 am

Re: Fuel tank breather

Post by smchris »

Hi John.

Forgive my ignorance, but what's "AC"?!

I'd welcome the replacement cap though; I would like to keep it original. I've got pretty much everything else as was. How much do you want for it?

Chris

Billy26F5
True Blue
Posts: 1912
Joined: Fri Jun 26, 2020 12:01 am
Location: On Billy

Re: Fuel tank breather

Post by Billy26F5 »

AC made the later type cap, as you can see in the pic.
Billy26F5 wrote:
Tue Aug 31, 2021 11:01 am
this one (Davie's one) is the late one, you can see the valve in the centre.
Image
Sandy
ImageImageImage

John b
True Blue
Posts: 537
Joined: Tue May 19, 2020 8:40 pm

Re: Fuel tank breather

Post by John b »

Sent you a PM Chris
My biggest fear is that when i die my wife will sell my tractors for what i told her they cost

Post Reply