UAT Problem...Help !!! problem cured !!!
 

OK here is whats happening. Started my P-80 for the first time today. All went well untill the UAT started to collapes went dry. It collapses and will not draw fuel from the main tanks. I thought it might be the tubing is too small but even at idle the UAT emties and does not draw from the main tanks. BUT when I bypassed the UAT the engine ran fine and emtied the main tanks !!!...Now some info on my setup. Two main tanks in series going to a UAT (BVM). All tubing 1/8 inside diameter tygon tubing. The UAT is 4 years old and was drained all winter just getting fuel today. Checked the UAT...didnt find and blockages...I saw a thread like this before but was unable to find it agian...any suggestions ?????

Thanks
Brian

P.S. the P-80 did sputter a bit at high throttle, but reached 123000 rpm and stayed there. (I am assuming air in line without UAT)

RE: UAT Problem...Help !!!
 

Are you using a foam filter in your main tank??

If so, there's your culpret.

RE: UAT Problem...Help !!!
 

nope ......no foam filter. Metal large size pickups

RE: UAT Problem...Help !!!
 

Hi, you may have to change the UAT's bag.

http://www.rcuniverse.com/forum/m_69...tm.htm#6920430

Good luck.

RE: UAT Problem...Help !!!
 

if you fill the main tank via the UAT (and you should be) and it fills without excessive resistance then there shouldn't be any problems with it with turbine running unless you've by chance got a 1 way Festo installed in the line between the main tank and the UAT.

if the UAT is collapsing the bag/filter in the UAT is not the problem, it's restricted on the input from the main tank.

RE: UAT Problem...Help !!!
 

you might want to check for proper venting.

RE: UAT Problem...Help !!!
 

Overflow nipple plugged?

RE: UAT Problem...Help !!!
 

if that was the case he wouldn't of posted.......



with the vent plugged it'll collapse the main tank as well.

RE: UAT Problem...Help !!!
 

Thanks for all the hints guys. Keep them coming...I have installed a new UAT and will try a new run Wed.

Thanks for your time

RE: UAT Problem...Help !!!
 

...not if they are fiberglass or kevlar..

There is a restriction somewhere between the nipple inlet on the uat, and the outside atmosphere (vent) A pinched fuel (or vent) line is one possibility.....

RE: UAT Problem...Help !!!
 

correct, it'll try to collapse them and then implode them till it develops a crack to allow air in instead. :eek:

RE: UAT Problem...Help !!!
 

Been there to often[>:] That #%&*&$ vent plug.
Dom

RE: UAT Problem...Help !!!
 

Yes, me to. I now have one of these red "remove before flight" tags attached to the vent pipe.

RE: UAT Problem...Help !!!
 

Why would he not have posted if he didn't know the vent line was plugged? Are you having a bad day?

RE: UAT Problem...Help !!!
 

I'm having a wonderful day, and yourself? i also read what is posted and when the UAT was bypassed it ran fine And drew fuel from the main tank. IF the vent was plugged it will collapse the main tank as the pump sucks the fuel out and there is no way for air to come in. if the tank is fiberglass or Kevlar then it'll bust hell out of it when it develops enough vacuum to do so, if you don't believe it, plug your vent, fire the turbine up and watch it.

RE: UAT Problem...Help !!!
 

Your post just seemed rude in your response back to me and I was hoping you were just having a bad day and not being rude.

RE: UAT Problem...Help !!!
 

i was neither having a bad day or trying to be rude, just blunt and to the point.

RE: UAT Problem...Help !!!
 

Thanks for the apology.

RE: UAT Problem...Help !!!
 

Thanks for all the ideas guys...Can we Pleeeeeze keep this nice. Vent was definately NOT plugged!!!

RE: UAT Problem...Help !!!
 

Maybe the UAT is pulling air in from somewhere ?

RE: UAT Problem...Help !!!
 

Try just running the pump without running the engine or you can use your fueler as the pump. This will give you a more controlled test without the distraction of a howling engine and you can check the lines and tanks more easily and closely with just the pump running.

RE: UAT Problem...Help !!!
 

Brian,

Do you have a filter between the UAT and the main tank?

Are you filling the main through the UAT?

Bob Michaud

RE: UAT Problem...Help !!! problem cured !!!
 

Thank you guys for all the hints. We cured the problem....I put in a new UAT and went in and replaced all the tank tubing. I think what happened was the fuel line pickup was able to move and get stuck in the forward part of the tank partially pinching off the fuel line. The partial obstruction caused the UAT to collapse and empty when the engine was running. When I bypassed the UAT the pump was able to overcome the blockage (kudo's to the jetcat pump)...all is running great and I made sure the klunk can no longer jam itself in the front of the tank

Thanks to everyone who took the time to offer advice

Later
Brian

RE: UAT Problem...Help !!! problem cured !!!
 

Glad you got it figured out!

RE: UAT Problem...Help !!! problem cured !!!
 

never make a tank clunk only with tygon tubing.
eather use 6mm festo (it wont bend forward)
or use copper tubing inside the tank..