79 fuel tank

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May 13, 2010 | 03:36 PM

Fair 96

Thread Starter

Laughing Gas

Joined: Jul 2004

Posts: 769

Likes: 3

79 fuel tank

I just got a rear fuel tank and it has a hole in the top of it. My old one does not any ideas on why.

May 13, 2010 | 04:13 PM

1993topdog

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Joined: May 2010

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most tanks are available with or without the "emissions" hole. Pre-'78 usually have no hole, most '79 have the hole. Ive seen people plug them with a rubber expansion/freeze plug. Weld it shut if you can.

May 13, 2010 | 04:16 PM

jmikeyj4

Senior User

Joined: May 2010

Posts: 169

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From: Akron,ny

is it for the fuel sending unit

May 13, 2010 | 04:21 PM

1993topdog

Freshman User

Joined: May 2010

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Sending unit is about 4" in diameter. Emissions hole is at the top of the tank, centered in a small dimple in the tank, 1"+/- diameter.

May 13, 2010 | 04:42 PM

Fair 96

Thread Starter

Laughing Gas

Joined: Jul 2004

Posts: 769

Likes: 3

Quote:

Originally Posted by 1993topdog

Sending unit is about 4" in diameter. Emissions hole is at the top of the tank, centered in a small dimple in the tank, 1"+/- diameter.

You are correct about the hole size and location. Is a mig with gas good enough to weld it with.
Thanks

May 13, 2010 | 04:47 PM

1993topdog

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Yea, MIG is fine. That's what i welded mine shut with. Careful not to burn through. The tack, tack, tack usually works better than full trigger pull for the duration of the weld on something this thin. I welded mine with a Miller 135 on heat range 4 with the wire speed at 60. Just make sure you get enough heat to avoid pinhole leaks.

May 13, 2010 | 04:51 PM

gus11208

Senior User

Joined: Sep 2008

Posts: 197

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From: near Pittsburgh

I always recomend getting a 78 bronco tank it fits within the frame rails you just need the bronco straps and sending unit and it gives you a bit more fuel capacity

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May 13, 2010 | 04:58 PM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

Posts: 88,826

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From: Simi Valley, CA

Quote:

Originally Posted by Fair 96

I just got a rear fuel tank and it has a hole in the top of it. My old one does not any ideas on why.

That hole is for the Evaporative Emission System's fuel vapor valve.

There were different tanks...with or w/o Evap Emission.

Instead of welding the hole, you could install the valve, then cap off the nipple on it.

Quote:

Originally Posted by 1993topdog

Pre-'78's usually have no hole.

That all depends on which state(s) the vehicle was sold new.

Evap Emission was introduced in 1970. All sold new in CA: Passenger Cars, most F100/250's, Bronco's, Econolines had Evap Emission from day one.

It was mandated by CA's strict emissions laws that vehicles under a certain GVW sold new in CA had to have it.

Other states in the 1970's required Evap Emission besides CA, so there's a lotta pre 1978 fuel tanks used with Evap Emission only.

btw: CA smog tests all 1976 and newer vehicles. If any of the emission parts are missing or are defective, the vehicle CANNOT be registered until it can pass a smog test.

There is no waiver if the parts are obsolete. It's fix it...or park it.

And...there's another associated problem if you park it without current license tags. The polizei can tow the vehicle away! I kid you not.

Aren't y'all glad you don't live here in CA?