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Thread: Raw Gas Smell

  1. Default Raw Gas Smell

    I have a 69 Tempest 350. The car is a low mileage car and and has been garaged since new. Since I purchased the car in 1995, I have smelled raw gas when running down the road and after I shut it off. I have replaced the carb, filters and everything I can think to do. I see no leaks and the car runs perfect. Nothing I have changed has had any effect on reducing the gas smell. Everything is stock on the car. I would appreciate any ideas.

  2. #2
    Join Date
    Nov 2008
    Southeast MI


    I would inspect and consider replacing every piece of rubber hose that comes in contact with the gas or gas vapor, including the small piece from the gas tank to your hard lines. Former Pontiac Historian, the late John Sawruk, would lecture about replacing rubber hoses with new modern hoses. Time, sun/UV exposure, dirt/road grim/road chemicals break down the rubber from the outside. Today's gasoline has been significantly reformulated to meet today's automotive emissions needs, plus it contains some level of ethanol. So it will break down old hoses from within. So replace all rubber hoses with new modern hoses. Judges do not deduct for the use of new hose.

    Inspect your hard fuel lines, fuel pump, gas cap, and gas tank for leakage. Do you have an external electric fuel pump? I would inspect the mechanical fuel pump on the engine first. If its leaking, you should be able to readily tell. If you have leaking fuel lines or gas tank, you have to follow your nose or find it dripping somewhere along the frame or under the car. Is the gas evap cannister connected correctly or at all?

    Assuming you have no carb issue, are you sure your gasket is sealed between the carb and intake?

  3. #3


    Thanks guys, looks like I have some work to do.

  4. #4

    Default What I have found so far

    I thought I would provide an update on what I have found so far.

    First, I removed the tank to repair the sending unit. The tank and sending unit showed no signs of a leak. The short rubber hoses from the sending unit to the fuel and vent lines both showed no sign of leakage. The front tank vent and filter looked fine also. The vent hose on the tank filler neck also showed no sign of leakage. The grommet from the vent to the trunk was cracked a little. I will replace all of these when the sending unit returns from repair. So, the only visible problem was the cracked grommet.

    The fuel and vent hoses from the lines to the fuel pump had been replaced earlier, and they also looked fine, but I will replace them anyway.

    I removed the carb, it's a two barrel Rochester, there was some gas stains on the manifold around the base of the carb. I took it to an old carb shop to have the carb checked out. The owner of the carb shop asked me if I had checked the fuel pressure of the fuel pump. He said he has found many pumps putting out more pressure that the required 5-7 pounds. He called me a few days later and told me that he found no reason (gaskets or settings) that would be causing the gas stains to be on the manifold.

  5. #5

    Default I finally found the problem

    After replacing all the rubber lines that had anything to do with the fuel system, the fuel sending unit, and rebuilding the carb, I finally found the source of the leak. It was a tiny flaw in the hard fuel line flange where it goes into the carb. It would leak just a speck about every 30 seconds. I could not really see what the actual problem was with the flange, but it allowed a tiny leak. We cut a tiny bit off the line and "reflanged" it and it's fixed. Thanks for everyones interest.

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