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Discussion Starter · #1 ·
Hi,

Yesterday, I drove my


Hi,

Yesterday, I drove my recently acquired '76 308 back from my mechanic who just checked out my mixtures (and who raves about how strong mechanically the car is).

This sounds odd, so bear with me - some facts:

1. The car runs as strong as new with great compression.
2. All fuel hoses were just changed (5 months ago) on this car.

Here is what my friend and I observed on the way home from the shop today (he was following behind me in his car):

After filling the fuel tank (topped it off until pump clicked) I noticed a smell of gas in the cabin - I naturally thought it was me as I had just gotten some on my hands.

During a sharp right-hand-turn on-ramp, my friend noticed some liquid spewing out of my left hand tailpipe region - he immediately notified me(we were in contact with each other via handheld radios) but I wrote it off as being from condensation as the car was not completely up to temp and he did not notice any steam or smoke. at this time, I smelled a stronger odor of gas, especially after making the turn.

This event happened again during the next right hand turn, and again my friend just observed liquid with little smoke - he also smelled gas from inside his car. I immediately pulled over and shut down.

The engine bay itself did not smell of fuel (only the cabin). I could not see anything leaking anywhere. I figured that no way would fuel be pouring from the exhaust as it would vaporize or catch fire first. But, the left tail pipe had a whitish stripe inside - as if something did indeed run out of it. Again, no leaks could be seen and the car was runnning better than excellent, all gauges "in the green".

After a while (after some fuel was used), this event did not happen again - my friend was watching me like a hawk. I made other turns and no liquid could be seen. Although, I still smelled gas during turns.

My questions are:

Could I have overfilled the tanks and during a right hand turn, fuel was sloshing into the left tank and overflowing somehow?

Is there a overflow tube somewhere and my friend could have mistaken it to be coming from my exhaust (but there was a tell tale sign, the stripe, in the exhaust that indicated something had ran out of it)?

How could it be possible for fuel to run out of an exhaust in a stream like my friend observed?

Of all the wierd problems I have heard, this one takes it......

Thank you in advance,

Anthony
 
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Discussion Starter · #2 ·
Anthony,

To best answer you


Anthony,

To best answer your question...and concern, I'll start by questioning the statement "All fuel lines were replaced..."

Based on your detailed description, there are two areas I would look at now...before driving the car another mile.

1) The fuel filler overflow hose, on the filler neck. Verify it's condition, tightness...and that the hose is long enough to exit a few inches below the lowermost frame rail. This hose likely is the culprit.

2) The fuel tank vent hose...Rarely changed. This usually is a semi-clear 13mm hose which connects the top of each fuel tank to the other. It runs from the top of the tanks across the firewall. Verify it's condition and tightness of connections.

This is not a wierd problem...or one that should be taken lightly, as the likelyhood of fire is real. Fuel and the proximity of a hot exhaust manifold don't play together very nicely.

I suspect here's what happened...

You may have overfilled the tanks (for reference, they are connected under the car by a cross-over tube.)

The excess fuel...instead of streaming on the ground, ended up in the frame, or lower wheel well fibreglass area...and when you pulled away...it worked its way out by the body opening for the LH exhaust. (The overflow tube exits on the LH side of the car)

To be safe, I'd inspect ALL the fuel lines...

Regards,
David
 
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Discussion Starter · #3 ·
Dave,

Thank you for your de


Dave,

Thank you for your detailed explanation. I have the workshop manual and its diagrams. I will check everything. I know this is a dangerous situation and will not drive the car another mile.

"The fuel filler overflow hose, on the filler neck. Verify it's condition, tightness...and that the hose is long enough to exit a few inches below the lowermost frame rail. This hose likely is the culprit."

Are you saying the fuel filler hose has another overflow hose connected to it which drops down below the frame rail? Should I see a small hose in this area?

Some of my evaporative emission lines are original (the braided lines). The vent line that runs on top, connecting the two tanks, looks to be original and probably should be replaced.

Thanks again in advance,
Anthony
 
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Discussion Starter · #4 ·
Anthony,
You're car likel


Anthony,
You're car likely is a bit different than my pre-smog BB. Either way, there is a fuel overflow hose...possibly your doesn't exit to the ground. Follow, the line off the filler neck...sounds like it might go to some sort of evaporative canister (versus the ground). These are the lines/hoses I'd be most concerned with. If there is a vent line, it too should be below the chassis frame rails. Sometimes, it is just visible, when looking in, just in front of the LR wheel.

Regards,
David
 
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Discussion Starter · #5 ·
>>Could I have overfil

>>Could I have overfilled the tanks and during a right hand turn, fuel was sloshing into the left tank and overflowing somehow? <<

This does sound likely.

Besides the things David has mentioned I've seen:

Fuel Sender Gauge Unit/Gasket loose/ hard gaskit/ improperly installed, causing leaks.

Gas Caps no good/not installed properly

Large Filler Rubber Hose Cracked/Loose Clamps/Dislodged

Lower Gas Tank Hose to Pump / Fuel Filter/ Fuel Pump/ Fuel Pump Hose to Carbs leaking .

and on the right side- fuel return hose to tank and/or Carbon Canister hoses leaking (especially under Cowl on Top of Tank.

Check all those areas while you're at it.

You can refill tanks from can at home and jack up left side of the car with a floor jack at the jack point to see if the problem can be induced while sitting, instead of chancing driving around.

HTH's
 
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Discussion Starter · #7 ·
HI,

In the parts manual&#39


HI,

In the parts manual's diagram of the fuel system, a "calibrated" valve is shown at the end of a very small tube, just above the filler neck tube, slightly below the fuel cap. Is this in fact a fuel overflow tube/valve? Does this valve allow fuel to exit during an overflow situation?

Thank You,

Anthony
 
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Discussion Starter · #8 ·
Anthony,

that's correct


Anthony,

that's correct...this is to prevent overflowing fuel from spilling near the exhaust. It is supposed to exit near the bottom of the Left Fuel Tank in front of the LR tire.
 
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Discussion Starter · #9 ·
Thanks, I'll have to remov

Thanks, I'll have to remove the wheel-well as I can not see this tube or the beginnings of it at the filler neck.

How can this still be considered a "sealed" system? - seems like vapors could vent through this too - unless it is some sort of float valve....Hmmm
 
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Discussion Starter · #10 ·
Hi,

Well I was under the ca


Hi,

Well I was under the car today and I am not very confident about what my problem is.

The "overflow" tube I see looks like it only catches any spilled fuel from the tray where the gas cap is. I did not spill any there at the time this happened and the cap was on properly and is a correct cap.

Now, this "calibrated valve" - I did see it. It was there just like the parts book displayed it (can you believe it?!). It is a valve just sticking out of the metal part of the filler, slightly above where the top of rubber filler neck hose is. It is pointing to the rear of the car, but has no hose attached to it that would carry overflowed fuel. It's just a small stubby valve. I can not find a description of this anywhere, just a statement that says "..to prevent fuel outlet" ???. Why would there be a valve here then in the first place!!

Does anyone know what this valve does? If it is unload excess fuel - it does not dispense it safely, as fuel would pour over the top of the tank. ?????

Thanks,

Anthony
 
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Discussion Starter · #11 ·
Hi Anthony,

sorry to hear y


Hi Anthony,

sorry to hear your issue isn't resolved yet.

Wish I had some concrete answers for you but I don't. I do have a 77-B with the engine out and I'll take some pics and have a close look at every thing to see what I can determine.

Regards, JRV
 
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Discussion Starter · #13 ·
Anthony,

ok, had a few minu


Anthony,

ok, had a few minutes to inspect this 77 left my camera at home).

Yes this 'check valve' is attached to a short lenght of hose to the filler neck with nothing on the exit side of the valve. I have never had to replace one of these so I don't have any personal knowledge of them going bad or what they do. However from the look of the attachment and configuration it looks to be a pressure vent. It appears this valve would vent pressure (fumes) in the event of an excessive pressure build-up in the tanks. I seriously doubt it is for venting liquid, however I suppose "IF" the fluid did get that high it would also vent the liquid. It would then vent the liquid onto the top/side of the gas tank and on the inner fender, letting the raw fuel run down onto the frame. However, it's unlikely it could run all the way back to the rear of the car, while possible, seems very unlikely, but, if enough fluid got onto a tire, it perhaps could have thrown the fluid rearward and out the back as you described.

HTH's

JRV.
 
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Discussion Starter · #14 ·
Thanks JRV, I was thinking tha

Thanks JRV, I was thinking that this would allow the tank to suck air to remain at atmospheric pressure also. You're right, I do not think fuel would run around to the rear of the car.

If it was my metering assembly or a seam on top of the tank, I still do not think fuel would have came out the rear. So, ow I am back to square one.

I am thinking about filling the tank, letting the car cool. Then restarting and making a sharp right hand turn to replicate the problem - not the best or safest way, but I would like to find out where any excess fuel is going.....

Thank you for your time,

Anthony
 
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Discussion Starter · #15 ·
Anthony,

one thing you coul


Anthony,

one thing you could try first is to pull out the check valve and test it to see if perhaps it's stuck open or closed.

To test put a small amount of air pressure on the tank end of the valve and see if it is constantly open or requires some pressure to open and then draw a vacum on the atmosphere end to see if it'salways open or requires some vacum to open..
 
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Discussion Starter · #17 ·
Well, my problem turned out to

Well, my problem turned out to be the obvious - which was not so obvious! ?

The leakage was coming from the fuel filler neck -there was a razor-like slit JUST below and parallel with one of the clamps (as if the clamp cut into it). This neck was supposed to ne relatively new, but it looks as though it was the wrong type anyway.

Thanks for all your help,

Anthony
 
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