Author Topic: Fuel smell 68 fastback  (Read 782 times)

pmustang

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Fuel smell 68 fastback
« on: July 06, 2019, 01:58:38 PM »
Hello Folks

I have a 68 fastback Shelby tribute. All the body mods are similar to a shelby of the same year so hope someone has an idea of how to sort

Upon acceleration a very strong smell of petrol enters the cabin

Floats in carb are set correctly and zero petrol smell at the front of the car

I understand it can be the fuel filler rubber tube, the trunk lid seal, gas cap, exhaust tips not being long enough or gaps around tail lamps

My question is, what do you use to seal around the tail lamps and rear panel?

Cheers  Peter

deathsled

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Re: Fuel smell 68 fastback
« Reply #1 on: July 06, 2019, 02:12:43 PM »
Look for leaky gas around the carb float bowl screws front and aft.  I fixed that very problem on mine. Loose screw was letting gas percolate up the top of the carburetor.

But then you did say no smell of gas at front of the car.
« Last Edit: July 06, 2019, 02:44:07 PM by deathsled »
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pmustang

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Re: Fuel smell 68 fastback
« Reply #2 on: July 06, 2019, 03:39:44 PM »
Thank you.  I will nonetheless look.  Its such a sudden and heavy smell of gas immediately after acceleration its uncanny

deathsled

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Re: Fuel smell 68 fastback
« Reply #3 on: July 06, 2019, 03:48:41 PM »
Check the engine compartment while the engine is at idle and look for leaking gas around the carburetor then check the fuel lines. Also, buy yourself a fire extinguisher for any emergency while on the road. I have one in mine and thinking of getting a second one.
"Low she sits on five spoke wheels
Small block eight so live she feels
There she's parked beside the curb
Engine revving to disturb
She's the princess from his past
Red paint gold stripes damned she's fast"

Side-Oilers

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Re: Fuel smell 68 fastback
« Reply #4 on: July 06, 2019, 10:37:08 PM »
+1 on fire extinguisher(s) on board, and make sure they're Halon.

If you're describing fuel smell and not exhaust, then I'd also surmise it's something leaking at/in the carb.

If it's exhaust smell, my KR has always done that. I've always attributed that to exhaust entering through the trunk somewhere.  Seems to be more prevalent at low road speeds.

But, that just smells like the 1960s to me.  Part of the old car experience.

I realize that you're a very knowledgeable Mustang guy, so let us know what you find out the problem is.
« Last Edit: July 07, 2019, 01:23:01 AM by Side-Oilers »
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shelbydoug

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Re: Fuel smell 68 fastback
« Reply #5 on: July 07, 2019, 08:00:28 AM »
I just had to change the fuel line. Seems 50 years old is a critical crossroad. The leak is usually just where you don't look.

pmustang

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Re: Fuel smell 68 fastback
« Reply #6 on: July 07, 2019, 03:21:22 PM »
Thanks folks

We have removed the bumper and tailight panel

Large gaps around the bumper mounts and zero sealing behind the decorative panel behind taillights

We will be dealing those up and see where we are

Also checking the carb as mentioned above but there is no smell at the front of the car.

It sure smells of fuel to me

Thanks for your suggestions. I sometimes think I know wuite alot and othern times nothing at all

shelbydoug

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Re: Fuel smell 68 fastback
« Reply #7 on: July 20, 2019, 01:27:23 PM »
There was a recall on the 69 gas caps because the venting was igniting with the exhausts right below it. Put a non-vented cap on and see if the smell goes away?

pmustang

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Re: Fuel smell 68 fastback
« Reply #8 on: July 20, 2019, 03:57:34 PM »
Update

I have used thick plastic to cover the openings in the twilight panel, heavy duty the to secure.  The rear panel attatched nicely and none of the plastic is visible from outside.  I trimmed around the tail lamp openings in the rear panel and the lamps clipped in securing the plastic perfectly

I have noticed the flip open gas cap is missing the seal on the spring loaded piece that seals the tank

I also think the exhaust tips may be a bit short

I have driven the car yet to see if the smell has reduced

Cheers for all the advice

Peter

Bob Gaines

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Re: Fuel smell 68 fastback
« Reply #9 on: July 20, 2019, 07:21:29 PM »
There was a recall on the 69 gas caps because the venting was igniting with the exhausts right below it. Put a non-vented cap on and see if the smell goes away?
Keep in mind that if you fit a non vented cap that you will have to add a vent somewhere else . You have to have a vent to allow air to displace the fuel in the tank as the fuelpump draws it out. In the case of the 69/70 Shelby the vent was added to the gas filler neck and routed over and down to the passenger side the wheel well and routed out of the trunk floor drop .
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

Side-Oilers

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Re: Fuel smell 68 fastback
« Reply #10 on: July 20, 2019, 08:55:09 PM »
Agreed with Mr. Gaines. 

This possibly/probably doesn't pertain to Mustang tanks, but I've been told that on Corvette tanks (C2 and C3) if you use a non-vented cap the gas tank itself can implode a bit as the gas gets used up and a vacuum inside is created.
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shelbydoug

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Re: Fuel smell 68 fastback
« Reply #11 on: July 21, 2019, 06:43:06 AM »
There was a recall on the 69 gas caps because the venting was igniting with the exhausts right below it. Put a non-vented cap on and see if the smell goes away?
Keep in mind that if you fit a non vented cap that you will have to add a vent somewhere else . You have to have a vent to allow air to displace the fuel in the tank as the fuelpump draws it out. In the case of the 69/70 Shelby the vent was added to the gas filler neck and routed over and down to the passenger side the wheel well and routed out of the trunk floor drop .

Probably some sort of a charcoal filter in that system would eliminate any possibility of fumes as well? You should be able to find one that works since all cars now have them new as part of the EVAP system.

67350#1242

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Re: Fuel smell 68 fastback
« Reply #12 on: July 21, 2019, 08:04:58 AM »
Without a seal on cap, fuel can slosh out upon acceleration, esp. if tank pretty full.  Even if the plastic stops the smell inside, you should of course address this issue.
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Bob Gaines

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Re: Fuel smell 68 fastback
« Reply #13 on: July 21, 2019, 10:31:39 AM »
There was a recall on the 69 gas caps because the venting was igniting with the exhausts right below it. Put a non-vented cap on and see if the smell goes away?
Keep in mind that if you fit a non vented cap that you will have to add a vent somewhere else . You have to have a vent to allow air to displace the fuel in the tank as the fuelpump draws it out. In the case of the 69/70 Shelby the vent was added to the gas filler neck and routed over and down to the passenger side the wheel well and routed out of the trunk floor drop .

Probably some sort of a charcoal filter in that system would eliminate any possibility of fumes as well? You should be able to find one that works since all cars now have them new as part of the EVAP system.
No extra filter needed for 69/70 gas cap vent recall because the fumes were vented to the outside of the car.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

pmustang

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Re: Fuel smell 68 fastback
« Reply #14 on: July 21, 2019, 12:47:55 PM »
Thanks folks for the advice, it is always appreciated

May I ask, if I want to install the cork gasket that is normally on the plunger portion of the flip down lid, what sort of adhesive I recommended?

Cheers. peter



« Last Edit: July 21, 2019, 05:15:14 PM by pmustang »