I smell gas on startup
 

I have a 89 S420 that has been working great for about 4 years, no problems at all. Lately when I start it I smell gas inside the car as if the fumes were being sucked in by the AC blower and out the air vents into the car.

I can't see anything wrong and the car runs great, I only smell gas at startup. There no gas leaks on the ground.

Any suggestions on where to start?

Sometimes when the oxygen sensor(s) begins to fail there is a gas smell at start up only.

If you have a small exhaust leak where the downpipe connects to the exhaust pipe it can cause that smell. When the engine is first started the exhaust has a strong gas smell especially before it goes through the cat. I had that exact symptom. But it could also be an actual fuel leak of course.

Rod, a leaking EHA valve could be causing the gas smell. Older ones develop hairline cracks that weep gas which can be observed best with a cold engine. Once the engine warms up the weeping gas evaporates so there are no tell-tale signs of a leak.

Where's the EHA valve on a 89 S420?
 

Just a little help when I open the hood, so I can find it quicker. Is it under something else, i hate those.

Thanks

take off the air cleaner housing and the eha is the black box on the side of the fuel distributor with two pin electrical plug .standing by left fender it is right in front of you.