The International Cessna^® 170 Association

Yep. Another uneven fuel tank drain post. Last summer we removed the L tank, cleaned the area around the filler neck, replaced the gaskets, and put everything back in. I noted black flakes in the sump for a few tanks but nothing since. But... that tank has been increasingly slow to empty. Wondering if there is a way to check for blockage without taking the whole darn thing apart again.

Fill the suspect tank only. Open the gascolator (removing screen to obtain full-flow.) Place a bucket beneath the gascolator. Open the Fuel selector valve and observe the flow-rate. It should flow 20 oz per minute. (This is approx. double full-power consumption.)

Amazing. This totally makes sense.