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Best approach to gasoline odor source

Here s the question in a nutshell: Does it make sense to fill the tank to capacity before the mechanic takes a look at it. 1990 Volvo 740 GL wagon, non-turbo, 160,000 miles. At first, I thought I only smelled gasoline after driving the car home and parking it, and I thought it was when the tank was full. No. Under 1/2 tank the odor exists around the fill cap area. It dissipates fairly quickly. (I never overfill). So, I thought fill hose. But then I took out the junk stored in the back, and can smell the gasoline under the same circumstances. No obvious drips. However, mileage has decreased, but I am driving short distances these days, not to mention that the car has not had a tune-up since I bought it 5 years ago. Tire inflation is solid all around. Driving speed is even. I do not smell the gasoline once the car has been sitting overnight.

I do not work on my car. I researched the problem, and it looked like taking a visual of the hose, etc., by removing the inside panel, was the best way to go, and it didn’t look complicated. My mechanic, however, wants me to fill the tank and immediately bring the car in to look for leaks. If no leaks are visualized, he went to a second option that sounded so unnecessary and time-consuming to me that I can’t recall what it was. He acknowledged that the filler hose could be the problem, but it was only after I asked about the direct visual check that he said that would be the third option.

. Thank you.

Gas tanks can rust on the top creating pin-hole leaks.

I’d pack the tank with gas and see if it starts leaking from the top of the tank.


Thank you. It has a plastic tank though.

Plastic ages over time and it might still leak. For instance, the BMW water pump body is plastic. A friend has owned several 5 series Bimmers, and he replaces the water pump after 5 years of ownership with a racing water pump, which has a steel body. I understand that the plastic BMW radiator overflow tank suffers the same problem.

BTW, he learned about the water pump the hard way.

Yeah I had a leaky tank on top. I only smelled gas when I filled it up. Finally crawled under it and felt the top of the tank. filled with sand wet from the gas. Pretty hard to see without pulling the tank though. Kind of fun though, I ordered the tank and it went from the east coast to the west coast and then another stop some place else before it finally landed in Minneapolis. Every time they traced it it was someplace where it shouldn’t have been waiting for me to pick it up.

Thank you. I understand that plastic will leak and weaken. But the reply was that the tank could be rusty.

An evap/smoke machine could probably be used to help

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That would not be my approach. I’d use the smoke machine. And probably the tailpipe sniffer (combustion analyzer). It can sniff out hydrocarbon molecules.
The car is 26 years old. Old enough to have a family. The gas smell could be coming from a rot pinhole, a leaking line fitting, a bad injector O-ring, a dried out fill pipe rubber fitting, or any of a dozen other sources.

Perhaps for this problem another mechanic would be more appropriate?


I am with Mr. Mountain Bike. Smelling gas so adding more gas to the vehicle just does not sound like a good idea. As with SMB and DB a smoke test seems like the best first step.


My 2003 Chrysler minivan had a plastic tank and I could not figure out why I had a constant evap leak code and could smell gasoline. Purge valve, hoses and canister all seemed good. Finally I saw gasoline stains on the passenger side of the tank.

It was winter so I took it to my mechanic and he found out the metal retaining ring for the fuel lines and mounting plate for the pump had rusted so badly as to leak. he showed me two tanks in his scrap pile that the ring had rusted so badly that removing it had created holes in the thread area of the tank. I was lucky, all he had to replace was the ring and fixture assembly. All the flexing from the failed ring had cracked the steel plate the lines run through.

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Just as a reference point… I have a truck that gave me a gas-smell but had no visible leaks and a plastic tank. The fuel pump and sender assembly corroded until a pinhole leak was created on the pressure line. The lines were zinc plated steel and had completely rusted through. Not enough to wet the ground but enough to smell.

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Thank you. My only choice is the mechanic who will do the fill-up and check, but I’ll sure ask him about the smoke/fogger.

Thank you. I’ll check it out.