Ive have an ’87 420 with 148K miles and occasionally I get a whiff of fuel in the cabin. I suspect it’s the EHA valve that needs to be replaced but haven’t done it yet. Today I was driving to the coast north of San Francisco. It’s a long, curvy, downhill road to the ocean -about 5 miles. I put the car in 2nd gear to save the brakes and let the engine do the braking for me. A short while into the downhill coast, the fuel odor became really strong. I almost got a head ache from it. Even with all the windows open I could still smell the gas. I even stopped the car and looked under the hood to see if a fuel line was leaking it was so strong, but there was no leak. I had just topped off the tank before I began the trip and thought maybe there is a crack in the neck of the fuel tank, and maybe I was dripping fuel from the rear but there was no sign of a fuel leak there. Also I dismissed the crack fuel tank neck theory because whenever I remove the fuel tank cap to fill up, there is always a good suction seal that I hear. But when I opened up the trunk it also smelled of fuel. Could this coasting in 2nd gear downhill make a EHA valve crack leak more pronounced? Or any other suggestions on where I could be looking for this fuel odor leak?
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Sounds like the symptoms of a cracked EHA valve to me. When the ambient temperature is cool and the engine cold remove the air cleaner, then start the engine. You should be able to see the EHA valve become wet/moist with leaking gasoline. The leak (at least on my car) is small enough that gasoline won't drip and if you check after the car has run for a while the engine heat will have evaporated any gasoline residue.

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Fred Hoelzle

Based on the statement about the fuel odor in the trunk, I'd say you have a problem in the evaporative loss system. This system is designed to keep Hhdrocarbons in the fuel system when the car is not running and burn them in the engine when the car is started.

Peter

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Auto Zentral Ltd.

Thanks for the replies guys. Here is what I have found out.
The EHA shows no dampness during a cold startup so I moved on to checking the Fuel tank Venting.
I pressure tested the connection between the purge valve and the charcoal canister and got good vacuum when I revved the engine to 3000rpm. I haven’t been able to test the charcoal canister yet because I can’t figure out how to get at it. Any ideas?

I then went to check the vent valve at the fuel tank. Problem is I don’t see it! The diagrams show it located near the fuel pumps. I don’t think it is there. This is not surprising to me because a fuel hose sprang a leak a while ago I was out of town so my son had the car towed to our idie mechanic, who replaced all the fuel hoses. It was after that that I began to get a faint whiff of raw fuel in the car. I thought it was residual gas from the fuel hose breaking. Could the absence of a vent valve be causing fumes in the car? Even so it still doesnt explain why the fumes have gotten so bad in the last few days, (if) I’ve been driving around without a vent valve for the last 4 months. The other thing I saw is that there is wetness from fuel around the orifice where the fuel vent line enters the gas tank. I’m hoping I can just tighten up that nut to stop that but that.

Your comments and suggestions are appreciated.

If they top up past where the pump shuts it's self off (we don't have self serve in OR) on my 500 SE on a hot day the cool gas from the underground tank will expand causing oder inside the car it's can be real bad if you park after a fill up..........

William Rogers.........

jrwierer, it seems that you've hit on the likely source of your problem. If it were me I'd talk with the indie mechanic who replaced the fuel hoses and determine if he failed to reinstall the vent valve. If so, he owes you one on his nickel.

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Fred Hoelzle

May sound funny but I had the same problem and turned out it was the gasket on the gas cap. Made a new gasket and the problem went away.

Incidently does this happen only when the car is over 1/2 to 3/4 full of full? If so, bet you anything that is the problem.

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