I need some help. I have a nice 940 wagon that has a gas smell outside the car from time to time.
I have pulled all of the hoses off the sending unit under the access panel. All were sound with no cracks or holes. I pulled the sending unit part of the way out and reseated the gasket. The gasket seemed a little big and didn't fit the sending unit tightly. I tightened the plastic ring pretty tight. It seemed like it sealed.

I left it all open and went to fuel up. Afterwards the gas smell is fairly strong at the sending unit. No visible leaks or gas anywhere.
I am thinking the seal is just not sealing properly because I can't come up with anything else.

Any thoughts or experience would really be appreciated.

Thanks,
Hawk

Hi,

It's hard to pinpoint it by smell unless you're a bloodhound. If you're sniffing around the sending unit, it could be coming up from anywhere below.

Don't forget the body of the tank itself. It may be just weeping and evaporating off the tank before it hits the ground. I don't know the 900 tank, but on the 240's I've seen pinholes on the top as well as, curiously, just below the center pinch weld. Also around the fill pipe. It might take you on your back with a flashlight and a mirror to do an inspection.

In the early stages they can be hard to find, but find it you must.

Good luck,
Peter

Dear maplebones

Hope you're well. 900 series cars' fuel tanks are made of a very heavy-duty polymer. Thus tank wall/floor corrosion won't be an issue. But road hazard damage cannot be ruled-out.

One way to track an intermittent and/or minor fuel leak is to tape clean, white paper towels around the suspected area. If fuel leaks, and then totally evaporates, it will discolor the towel. Wrapping the paper towel can be tedious. But it is a (no pun intended) sure-fire way to see if there's even minor leakage.

That said, I'd guess that the problem is the mal-fitting fuel send unit seal.

Hope this helps.

Yours faithfully,

Spook

Check the metal pipes at the top of the sending unit for severe rust. That did in the sending unit on my 240. No fuel or metal cracks visible from a quick perusal. Turned out the pipe was cracked at the junction with the sending unit top or "cap". You might need to pull out the unit to see this. Can't remember - long time ago....:)

Hi,


"I have a nice 940 wagon that has a gas smell outside the car from time to time"

IME regarding gas smell, the evaporative charcoal canister should be checked. The canister is automatically purged (its gas fumes sucked out) by the engine when in use. Check the vacuum line going from throttle body to the canister. Also check the brass nipple at throttle body where this vacuum line is connected. And clean any crud/carbon deposits there (may need to use small wire to clear any crud if this was long neglected). The rubber/hose connections at the canister also may have gone cracked and need replacement. Check for all these.

Any recent work on the sending unit may spill some gas outside plus its surrounding. Give a few days before reassessment.

Regards,
Amarin.

... as it can lose seal and positive pressure inside the gas tank passes through it.

The o-ring or seal atop the securing thread or (more so after market gas caps, such as a locking cap) can fail. The Volvo-brand gas tank caps, both locking and not, are resistant to seal failure save for an aged o-ring seal.

Some nations and states, provinces, prefectures, and the like therein, will test gas cap seal as part of emissions inspection.

Hope that helps.

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Had this on a 740. It was the return line on fill up only.
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Post Back. That's whats makes this forum work.

Are you sure that you checked the large hose that attaches to the sending unit that has a smaller hose branching of off it? They crack where the two hoses are molded together.

I did check it (the main fill hose) closely. I pulled it completely out of the car and examined it closely. It did not have any cracks, etc. I am confident it was sound.
It seems like the only thing left is that main sending unit seal, it just seems so unlikely that's it but I am going to try that next. The ring did not spin on easily. I started it and then had to tap it with a hammer and wood block to seat it. I would replace that ring but i think its NLA.

I plug the send of the canister hose and pressure the other end of it with my mouth (I know) it held pressure fine and was clear. The nipples on the TBody were clear.

Thanks for all of the ideas.

Seems like if it is the seal on the sending unit I should be able to smell gas whether the engine is running or not.

I'll report back.

Hawk