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Posted for "George/Shirley Shattuck" <kloop@plantationcable.net>:
I would like to post this to add to the information base for those who are
building a 320 or are flying and concerned about the hydraulic power pack
and its performance.
My 320 is a 1989 kit, finished 12/94 and now with 1053.8 on the TACH.
Problem: In May this year my pump started cycling more and more often,
finally running in half second bursts every 10 seconds or so. Also, more
frequently, the gear would not come down with the switch until I cracked the
dump valve for a second then closed it.
Solution #1. I changed the dump valve think it was leaking the high
pressure (gear up) side over to the down side. Improvement but still have
the pump cycling.
Solution #2. I replaced the high pressure switch. Again, a perception of
an improvement but still the pump cycles too often.
Major problem: In mid July and off on a trip, at cruise and after about 30
minutes, the pump started cycling more and more often until it finally came
on and stayed on. The gear stayed in the wells, I pulled the pump/relay
CB's, returned to my airport. The gear came down normally after the CB's
were in and gear down selected.
Solution #3. Using caps and plugs (borrowed from Bill Harrelson-thank you!)
I closed off the gear up lines at the three actuators first, selected gear
up and the hydraulic pump cycled continuously, at the rate of about three
bursts per second. I had suspected that a seal in one of the three
actuators was blown, I did not really suspect the pump as the problem.
After conversations with Oildyne I decided on a new pump over an overhaul of
the 1989 pump. I spent two full work days this week in and out of the aft
end of my airplane and with the new pump installed and three test flights my
problem has been corrected and I'm up and good to go.
I'm attaching a picture of the installation on the back of my baggage
bulkhead, including my nose. The block of foam attached between the
hydraulic lines is to prevent vibration. It turns out that the black wire
from the motor (ground) must go to the mounting bracket, then on to the
negative ground or my motor would not run. I brought that wire (#10) direct
to the negative post on the battery.
So, the symptoms can mean an actuator is the culprit, as I was advised, but
the old pumps like mine are a weak link.
I hope this is useful in the information bank.
George Shattuck
N320GS
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