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Tuesday, April 23, 2024

Doug's Domain

Doug Vetter, ATP/CFI

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Thursday, April 26, 2007

Fuel Leak

As I often do, I filled up the tank on the way home yesterday. The attendant managed to top off the tank with a total of 13.5 gallons, or about a gallon higher than I expected, but it didn't surprise me since the guy did the classic "oversqueeze" at $39 and for some unexplained reason decided to proceed to $40 in spite of the fact that I was paying by credit card. Aside from pondering why the idiotic New Jersey state legislature considers it illegal for an average citizen to pump our own gas when virtually every other state in the union couldn't care less, I didn't think much of it and continued home.

I arrived at my car this morning to go to work and stopped just short of opening the door when I smelled the distinct aroma of gasoline. I did my best impression of a bloodhound and walked around the car, then around the garage, all in an effort to exonerate my baby. I quickly realized that the smell was indeed coming from the car and was strongest near the driver's door so I took a quick peek under the vehicle only to find the bottom of the fuel tank wet with gasoline. It wasn't a steady leak and a quick turn of the key in the ignition showed I still had a full tank, but given that I had no idea of the real extent of the leak or where it was coming from, and given its proximity to the exhaust, my piloting judgment kicked in and I stopped the "preflight" right there and declared the car "unairworthy". I didn't have a flashlight, tools, or the time to dink around with it so I ran back inside to get the keys to the E46, as I concluded I'd be driving that to work today. As I pulled the E46 out of its lair for the first time in a week or more, I looked back at my E36 and felt sorry for her. She was built to drive, but she was getting the day off whether she liked it or not.

I drove over to the dealer to talk with my tech. I found him with his head wedged under a mostly dismantled dashboard of a new 7 series. So as to not startle him, I gave him the usual, polite greeting "hey, quit laying down on the job, you slacker!" When I asked what he had gotten himself into he rolled his eyes and admitted "heater core". Hmmm. That looked familiar. Anyway, I told him what happened. When I told him that I had recently topped off the tank, he immediately said it likely had to do with the sealing ring around the suction unit. I related that I had replaced the pump, suction unit and sealing rings over a year ago and never had a problem before. But then I remembered....the attendant really oversqueezed this time...more than they usually do. Could it really be that I didn't tighten the locking ring enough to create a perfect seal? I'll save you the suspense. The answer is yes.

This evening I pulled the bottom seat cushion out of the car and removed the inspection plate over the suction unit to find an even stronger smell of gas. A bunch of dirt and leaves had collected in the center of the suction unit so I had to vacuum that out before I could see that the leak was in fact due to a poor seal between the tank and the unit's sealing gasket. I pulled a large flat-blade screwdriver out of my toolkit and rapidly and lightly tapped the locking ring clockwise. I was surprised that it rotated a solid half turn before snugging up nicely. It certainly wasn't loose like that when I installed it. I suppose it's possible that the "dryness" of the rubber prevented me from achieving the correct torque, but I'm not exactly sure what cause this to loosen up. All I can recommend is to use some fuel lube or other rubber-safe lubricant during assembly so the locking ring won't bind up and give the false appearance of being fully tightened.

I cleaned up the area adjacent to the locking ring and under the car as well and took the car out for a spirited drive to burn off some gas. When I returned home I grabbed my hideously bright white LED flashlight and my telescoping mirror to look for leaks, particularly around the hardlines where they convert to rubber fuel hose. The supply line is always under pressure, so a leak at the fittings would be most evident there, but everything appeared dry now. The hoses appeared to be in relatively good shape, but I've added replacement of those hoses to the plans for later this summer. Mike Miller of BMW CCA has advised more than one owner of a 10 year old BMW to replace the fuel hoses, so I don't think I'm overreacting when I say "it's time".

Mileage: 142850