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Gas Tank Vent Tube/Hose--Necessary?

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KVH

KVH

Obi Wan
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My TR4A gas tank has no vent. The "TR4" parts catalogue shows a vent.

Anyway, my tank has a leak and two rust holes, so I ordered a new one. It is for all of TR6, TR4 and TR4A. It has a vent, curious enough.

What do I do? I can't see any vent hole for a tube, and since my current tank has no vent, should I just shut the vent with a plug?

Should I drill a hole in the body and put a vent tube down below the Chassis.

I'm reluctant to do anything non-stock, but the question is: Is there supposed to be a vent on the TR4A???

Thanks in advance guys.
 
Yes, you must have a vent. In the time of the 4s, the venting was done through the cap. By 6 days, that was no longer the case, and the venting went through a carbon cannister.
If there is no vent, then air cannot replace the gasoline as it is pumped out, and the tank will actually collapse.
If you can get a vented cap on the tank, then you can plug the vent tube in the tank. Otherwise, you'll have to have a vent hose from it.
 
My TR250 gas tank does not have a vent. Am I to assum it is done through the magnetic cap?
 
I have an original factory workshop manual for the TR4/4A (I've kept it when I sold a TR4A in 1977) and on Page 5-236, Fig. 67, it clearly shows a vent pipe with a banjo bolt located on the top of the tank on the far right front side (seen from the boot). FWIW
Curiosity just got the beter of me. I went out and removed the trim panel and verified that the TR250 does NOT have a vent pipe on the top of the tank. There is a vent hole on left side of the cap assembly below the rim of the alloy filler. Perhaps the later TR4A used a similar setup. It would have simplied tank installation at the factory and saved a few pence.
 
Thank you, tha is one less, possibly missing part to worry about.
 
Well, the tank I pulled out had no vent. So after reading these posts, I pulled the chrome filler cap off, turned it upside down and blew up through the "cap pipe." Air goes through, so I guess it's vented somehow. I hope that's the answer. I can't imagine that I'd have to drill a hole in the trunk area and drop a vent hose down near the exhaust pipes. That idea gives me chills. I'll let you know what I learn. Thanks for the info and help.
 
I know this is an old thread but, does anyone know how to tell if your Gas cap is vented? I know my tank is not but has plugged holes to vent it. Should I have a a vented tank and how should I run the vent pipe?

I have a 63 TR4, and I don't see the "There is a vent hole on left side of the cap assembly below the rim of the alloy filler." Vent hole.

Anyone have a picture of the tank vent connection ?


thanks,
 
As mentioned in the earlier posts, the tank must have a vent one way or another (through a tank vent, the cap, or the emissions plumbing). I have never seen a tank collapse from not having the vent. However, the fuel pump will eventually NOT be able to pump gas when the vacuum builds up.. and the engine will stop. So you must have a vent somewhere.

I am not sure how to tell you to test your filler cap to see if it is vented. As was mentioned above, on some you can blow through the cap verifying the vent is present.
 
All, If you do a lot of short trips and have a half full tank, you will never be able to figure out the venting system. Fill up, drive twenty miles, and then try and open the cap. If you have to struggle to get it open, you need a vent hole somewhere. In a lot of the later TR's the whole cap housing had a hole in the side, with a threaded connector, just below the panel for a vent hose, mine needed to be drilled and tapped, going to one side the of the car. I use this on the TR6 and it works fine.
With so many people not smoking now, the odds of someone throwing a fag under the left rear wheel surely must be down since the 1950's. You have to wonder if it ever happened.

Wayne
 
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