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600 coupe, one of the very first built
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102 Posts
Purge (MOT) valves can be cleaned. Take a 9V battery and apply to the connector.
There should be an audible click and you can spray carb cleaner fluid into the opening.
Do it a couple of times.
If no click, the solenoid is dead and the valve stuck.
 

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Discussion Starter #3
Purge (MOT) valves can be cleaned. Take a 9V battery and apply to the connector.
There should be an audible click and you can spray carb cleaner fluid into the opening.
Do it a couple of times.
If no click, the solenoid is dead and the valve stuck.
I meant the valve on the evap canister. I’ve already replaced the solenoid because the plastic housing was falling apart thanks for reading
 

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600 coupe, one of the very first built
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102 Posts
I meant the valve on the evap canister.
This must be an add-on for the OBD-2 compliant cars. Mine is an early model and has no valves on the canister itself.
I had shared the diagram of the system in another post:


The system is rather simple - one line is vent, one is for fuel vapors coming from the tank and the third one goes all the way to the engine bay, where the purge valve(s) is(are) located.

If you have something else in addition to the three lines that go in/come out of the activated carbon canister, do you happen to have at part #?
 

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1999 S500; W140.051
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711 Posts
I have a '99 S500.

I have not had to replace the valve at the cannister. I have had to replace the one in the engine compartment (MOT) that it sounds like you have already replaced.

I did clean and lube the MOT valve before I replaced it and it did work for a while. There was never a problem with the solenoid clicking, but it appears that there was a problem with the sealing of the valve.

These valves are difficult to troubleshoot so I don't think it is worth the hassle of trying to limp the old part along with cleaning.

Evap system errors are a pain in general to troubleshoot and driving along with flashing fuel light is annoying.
 

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1994 s600 coupe
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414 Posts
my car has a vacuum lock on the gas cap when I first got it. i.e. I'd try to open the gas cap and it was being sucked in by the vacuum in the tank, with the car off and just sitting there. not good. the cannister purge must have been stuck or malfunctioning. I disconnected both purge lines going to the throttle bodies, and capped the fittings on the throttle bodies. I leave the lines hang there open to vent the tank. I also only lock the gas cap half way. there have been issues with the W140 tank experiencing venting lock and blockage causing the tank to collapse and/or fueling problems. these I have read about online in repair advice threads. a blocked venting system will make the fuel pumps work their asz off trying to pull the fuel out, and burn up the fuel pumps. the reason my car was parked 6 years ago by original owner was, the fuel pumps died. I had to replace them to get it running. my advice is disable the cannister purge system. cars made prior to around 1975 had no charcoal cannister purge at all, it was another early emissions control system foisted onto the public. those systems are useless and total overkill if you live in a suburban or rural area. stored fuel emissions are only an issue in an overcrowded urban/big city area.
 
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