Fuel drip form Silver Hawk servo.
 

I operate an RV7A fitted with a 190 Lycoming Thunderbolt and a Silver Hawk EX 5VA1 Fuel Servo.

Total time is about 80 hours.

This is a new problem.

When parked in the hangar, tanks off, throttle and mixture fully back, fuel drips from the bottom drain of the inlet manifold (sump) immediately aft of the servo.

In the picture I have added, the outlet is in the bottom left hand corner under the red airbox.

Can anybody tell me what is the likely cause please?

That is your sniffle valve and it's there to prevent an accumulation of fuel in your intake manifold after shutdown. Essentially, this is residual fuel from the last pulse of the mechanical fuel pump. Why this is just now showing up after 80 odd hours, I don't know.

There are a number of threads on VAF dealing with this. Search "sniffle valve" and enjoy. A number of people have simply just put a plug in the sump. I'm undecided at this point.

Thanks Mark. Sniffle valve is a new term to me.

I searched it and found some brilliant answers.