Guys,
Has anyone had a problem with fuel getting poisoned from having a length of brass tubing for fuel pickup in the fuel jug? I have recently run into a problem with the engine starting, running rich then just cutting on the ground. I put the engine on the test block to work through the problem. First thing I changed was the tank, swapped it out for a new clean plastic tank. Same thing happened, start, run, quite. Next changed plug, no change. Next removed the fuel filter, no change. I am now down to only one thing that is common - fuel.

I have my fuel (5%N, 28% oil) in two containers, one is the 1 gallon plastic jug, second is a 1 quart tin can that I modified the cap to have two tubes, one vent the other to the bottom for fuel loading. The tube that goes to the bottom was brass. A few weeks ago I noticed a slight green tint to the fuel in the can. It wasn't noticeable when you pulled it into the fuel needle so I forgot about it. Once the engine started acting up I remembered the tint and decided maybe it wasn't good to keep brass submerged in fuel and that it was causing the green tint. I clipped it off above the fuel level and put plastic fuel tubing  in its place.

What I'm wondering is if the brass poisoned the fuel to cause the sudden cut out? I know aluminum can kill plugs but I never heard anything like that about brass tubing only that it can crack inside the tank. Anyone have this experience?

Best,        DennisT

Guys,
Problem solved. I had built a 1qt tin fuel can that fits in a section of my field box. I modified the cap to have a fuel feed tube that went to the bottom of the can and another short tube for a vent. These were brass tubing. Seems that brass tubing that sits submerged in raw fuel reacts with it and poisons the fuel. The longer it sits the more the brass reacts and the worst the fuel runs. In my case I had a quart that sat full for a couple weeks. This fuel would start and after about 30-45 sec the engine would just cut. I changed tank, plugs, props, and engine with the same results. This left only the fuel as the component that was unchanged.

Today I did the test with fuel that was only from a plastic jug, no brass contact. Engine ran perfect, solid 4 cycle, would break to a 2 when the nose was pointed up then back to 4 once leveled. I knew that aluminum particles poisons plugs and that brass tubing in tanks could develop cracks but not that it could poison fuel. You learn something new all the time in this hobby.

Best,         DennisT  

During one of the nitro shortages-- 1980 or so-- some Chinese nitro appeared on the market.  It must have had nitric acid or something in it.  It dissolved both the brass and the metal can.  It was bad stuff.  I've gotten Chinese nitro since then that has worked fine.