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)

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

If so, there's your culpret.

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

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

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

Good luck.

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.

you might want to check for proper venting.

Overflow nipple plugged?

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



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

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

...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.....

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

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

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

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

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.

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.

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

Thanks for the apology.

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

Maybe the UAT is pulling air in from somewhere ?

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.

Brian,

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

Are you filling the main through the UAT?

Bob Michaud

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

Glad you got it figured out!

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