peterman1

hey guys i had a fa-72 in my gp u-can do 3d until i crashed but before the crash i noticed i had a lot of fuel after flights in the engine compartment..well to make the story short i put the motor on the test stand and found that fuel is leaking from the back of the motor...from what i can tell its coming from the plastic end cap behind the crankcase...has any one had this problem before and know what im talking about....ive only had the motor for a year and before its was in the u ca do 3d 46 i had in a gp p-51...thanks for any comments..

pete

phread59

Hello Peterman, Take a good look at the backplate. You will find what looks like the nipple on the muffler for pressurizing the fuel tank. Is the fuel coming out of this nipple or in this area? Does the engine run ok? If the engine is running good and the fuel is comming from this nipple all is well. That nipple is the crankcase vent. It is there to allow fuel that is forced into the crankcase for lubrication to flow out. This is normal and nessesary to allow the crankshaft and connecting rod to get lubrication. Just take a short length of fuel tubing and rout it out of the engine compartment. Best is out the bottom of the plane. It will get gunk on it but this can't be helped. Anyway check the nipple, if it is the source of the fuel you will know what to do.

Mark Shuman

bentgear

On the 72 the nipple is on the front of the engine. That does not mean that its not the cause of the problem as it may be running back to the rear. That should be fairly obvious.

I would think it would either be the carb leaking fuel, maybe out the air intake, or there have been some reports of the back plate on the 72 cracking. I am assuming that you have already checked the screws holding the back plate on and they are tight.

Ed M.

peterman1

yes i have about 2 feet on tubing running from the nipple to the side of my test stand..also i noticed when the engine is cold it would leak more but after running it for a while the leak starts to slow down but does not stop. the engine runs fine but i have a hard time getting it to idle but after it runs for a while it seems to idle better...thanks

pete

ps i noticed where the chrome line coming out of the carb and into the motor is loose..i can pull back on the carb and the chrome line into the engine block will move...is this normal...could i have had to much pressure pulling back on the carb when it was in my p-51...hummm i wonder

peterman1

yes the screws are very tight

bentgear

Pete, one thing worth mentioning, thats a lot of restriction on the breater line. This builds pressure in the crankcase causing reduced performance, and I guess it could cause some blow by out the rear of the case if it does not have have a good fit.

One other thing to check is you may be too rich on the low end causing fuel to drip out the carb. The chromed intake pipe is held in place by o'rings, so it you pull on it it will move.

Ed M.