Expansion Tank Fuel Smell Quandary...

[Missed Approach]

Background- (1986 Coupe 3.2) Back in 2014, I replaced all the lines around the expansion tank (Part #8) including lines #9, #5 and #6 due to a heavy fuel smell leaking into the cabin. I also replaced the thick rubber Fuel Filler Neck Sleeve (911-201-515). That seemed to have solved the issues.



A week ago, I noticed (very slightly) the smell starting to reappear. I opened the Frunk, and it was clear the odor was coming from somewhere around the tank. Getting my nose closer, it appeared to be line #9.

Ordered new line from our host (now under Part#N-020-359-1-OEM). It came in a 1-meter section, and I only needed about 16 inches. It’s a bit of a pain to fish around the bottom, but it was still a straightforward install. Now here’s the odd bit… when I removed the old hose, it was filled with gasoline. Essentially, Hose #9 does appear to be the low point in the system.

I suspect I may have inadvertently caused the issue three seasons ago. I took the whole, “fill up your tank to the top” for winter storage too seriously. I way overfilled the tank. When I got home to put her away for the season, the warmth of the garage expanded the gas and she had quite the drips from the overflow system. I actually then had to drive for around 30 minutes to get the fuel level lower and ventilate everything.

The hose does appear to be marked with a date code- I’m thinking the “13” and “17” are the year of mfg. Is that correct? More importantly, the gas smell has not returned, but could an expansion fuel line break down in 6 years? (Assuming it was made in 2013).

[Bob Kontak]

Originally Posted by Missed Approach

I suspect I may have inadvertently caused the issue three seasons ago. I took the whole, “fill up your tank to the top” for winter storage too seriously. I way overfilled the tank. When I got home to put her away for the season, the warmth of the garage expanded the gas and she had quite the drips from the overflow system. I actually then had to drive for around 30 minutes to get the fuel level lower and ventilate everything.

That fuel has sat in the hose for three years, betcha.

I am just talking from the armchair but if the hose was filled gas could it seep out at the clamps? I mean, it had a little time.

Are the hoses fuel hose or vapor hose? I don't know if it should matter, but maybe.

Is the charcoal canister system working in the rear end of the car? There should be air box intake vacuum applied to the expansion tank system to pull vapors through. Don't know if it's strong enough to pull a slug of gas through the fender and deposit it into the expansion tank, tho.

[gomezoneill]

Can't help with the leak, but very nice photos dude.

[Pedro '84 Coupe]

The fuse box is definitely in the way. I unbolted it and see it aside as much as possible to get to that hose. It was quite difficult otherwise.

It's very possible your overfilling it may have had something to do with gas being in that hose. From what I understand, these are vapor hoses only and shouldn't carry gasoline, but I could be 100% wrong

I replaced all the fuel lines in my car and was still getting a fuel smell in the cabin. You said yours seems to have dissipated, but if it comes back, do a smoke test to see where the leak is. Had my mechanic do that for me and he found some holes at the top of the tank (this was caused by a DAPO who drilled holes into the tank when he mounted an amp). Sometimes the fuel filler neck itself can develop leaks too.

Agree with gomezoneill - nice pics!

[Missed Approach]

Hi @Bob Kontak, @gomezoneill, and @Pedro '84 Coupe- Thanks for the great feedback! I believe the hoses are technically barrier hoses, so not sure if they are truly able to take a slug of fuel, and (as per Bob) they probably can't take a slug for 3+ years unmoved.

I did find a NOS Charcoal Canister, and that's a winter maintenance item I intend to swap. I went and checked again tonight, and the smell is definitely gone from the cabin, so this hopefully did solve the issue.

[spyerx]

Check the filler neck hose too. On my former 89 i was getting a little smell in frunk. Replaced many of those lines but replacing the filler neck hose did it. It was quite cracked on the inside on removal. I went through that car and replaced every piece of rubber and hose and fuel line on it.

[88911coupe]

This seems like my problem and after sitting for few days with windows closed I can detect faint fuel smell in cabin but that took a while. Every hose in trunk replaced including the expansion tank and the large sleeve on the filler pipe. If I get my head close to the filler pipe and the fuse box I can definitely smell fuel. Could this be related to the evaporation tank in the wheel well or its lines? I’m not too clear on exactly where those go. I’m surprised replacing all the hoses and expansion tank had no effect.

[Missed Approach]

Hi 88911coupe- Whoa- this goes back 6 years! Per my initial writeup, when I removed line #9 there was a big slug of fuel in it, undoubtedly due to my winterization overfilling. I would recommend pulling #9 and check if there is any fuel in the line. It's been 6 years since my fix to a fresh line and no issues!

[88911coupe]

Thanks, I’ll check that. If there is fuel unit how are the fumes escaping?

[EC900]

If you recently topped off your gas tank and or spilled any gas and it ran down to the overflow tube, you might experience some lingering odor.
Gas should not be entering the fuel vapor expansion line unless there was an overfilled tank and some really wild turns and curves.

“… Could this be related to the evaporation tank in the wheel well or its lines? I’m not too clear on exactly where those go…”

Not sure if ‘88 has exp rank in fender well like the 74-77s +…with the washer fluid tank and the fuel vapor expansion tank behind it - but if so, did you did all the replacing hose and expansion tank, (or someone else) then make sure lines are correct that fumes are being drawn by vacuum back to into engine and charcoal canister is connected. If I recall it’s not easy to mix up lines due size of hose stubs, as for vacuum…It’s a 4mm hose and gets very brittle back there in engine compartment, if broken then no vac and odors could be backing to a weak connection in the trunk.
Smoke test the expan. system is one method, low pressure 1 psi max. But if you don’t have a smoker, just use air and be quiet enough to hear any hissing.

There’s plenty of diagrams for the expansion vapor system showing the route and connections.

Also, cabin to engine compartment is not so air tight either, so check that odor isn’t from a fuel line hose back there just in case.

[88911coupe]

Thanks EC900, tank was filled a few months ago and I've only used about a quarter tank (car rarely driven). ALL lines and expansion tank in trunk new so I'll focus on the lines to and out of the tank in the wheel well. I'm not clear on the route of the line(s) from the fuel tank/trunk are to the wheel well but I'll figure it out. I'll also look at the lines associated with the charcoal canister. I suppose if those are faulty it could cause vapors in the trunk to accumulate there?

[PeteKz]

The expansion tank on my 1973 was cracked. It wasn't obvious until I got it out and closely inspected it. I know it's not the same as later cars, but check it carefully.

[Koizumi]

Frankly I gave up years ago chasing my own tail with this. I replaced seemingly every part, to no avail. This still bothers me, I might attempt to take this on again. Where to start tho? I thought I had come to some sort of acceptance of failure on this issue!

[88911coupe]

I wanted to follow up so others don't go through what I went through. As I menioned I replaced every hose in the trunk I could find related the the fuel tank vapor system, but still was getting strong fuel smell near the large rubber sleeve that connects the fuel tank and the large fuel filler pipe. The rubber sleeve was BRAND NEW so it couldn't possibly be the leak...WRONGO...I decided to order brand new "Posche" version of the sleeve from our host and problem SOLVED. This has dropped on forever and very relieved to have a fuel smell FREE trunk. The NEW sleeve seeped fuel just like the old one and it was not enough to be wet but vapor came right through it immediately.