cannot trace fuel smell

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sraouf

New Member
Joined
May 19, 2015
Messages
11
Car
S124 280E
Can anyone help with tracing a faint raw fuel smell at the front of the engine bay behind the fan shroud between the air filter box and the block? Ive removed the air filter box and checked the fuel pressure regulator, the injector rails as well as the pipes/hoses around the fuel pump at the rear but cannot find evidence of a leak anywhere. The car is a 1993 S124 E280 with an M104 engine.
Thanks
Sam
 
Hi Sam,
Had a similar thing a couple of years ago on my E320 coupe. Changed the tank but it didn't solve the problem. I turned out to be weeping from the top of the fuel lines (The part of the pipes next to the chassis) Once both the supply and return pipes were changed smell went away.
 
Could be the fuel tank evaporative system charcoal filter . This is designed to trap and burn fumes from the petrol tank. There's a line[ like a brake line but slightly thicker] from the tank at the rear runs to a charcoal canister filter under the passenger front wing [ its behind the wheel arch liner so you won't normally see it] to trap fumes. In turn this is connected to the inlet manifold and periodically the canister is evacuated by engine vacuum via a small solenoid valve under the bonnet controlled by the ECU. Any leaks or malfunction with this system might give a fuel smell--- the charcoal filter is supposed to be changed every 70k miles or 5 years but is often neglected.
W124 Pressure in Fuel Tank

Other possibility would be worn injector seals where they enter the manifold
 
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I think I found the problem. Couldnt find any perished/damaged hoses so bought a cheap electronic sniffer (£15) and the vapor was strongest around the cam cover. I took the cam cover off and found the cover seals to be as hard as rocks (explains the oil seepage into the engine bay) and 3 of the 12 cover screw threads. were stripped, finally one of the spark plugs was loose. One of the spark plugs was also loose. The combination of all of this means that fuel vapors were escaping into the engine bay and blown by the cooling fan into the cabin. Helicoiled the stripped threads, replaced the seals, tightened the spark plugs and smell seems to have gone (although early days)
 
Good work!
Saved a few quid if this was DIY (I'm assuming it was).
 
yes saw another post that indicated that MB charged close to £500 for the same work. Only took 2 hours and parts cost around £30
 

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