|
pressurization
Alan
Here are some suggestions
1) can use a leaf blower and couple to the venturi or cabin inlet from upper deck. Works great. There are fittings for a ground tester, however, it is hard to find a facility with one (ground cart). The leaf blower can give you lots of air. A blower on a shop vac doesn't work well enough.............
2) look at the grommets or boots for the cables entering the cabin. These deteriorated because mechanics used GREASE or wrong form of silicon. They can cause problems. Located in base of struts and up in the wing roots. I can guarantee these are shot!
3) check around windows. Etching from repainting has caused major problems with windows leaking. Important point for new AC buyers. Warning for those that are going in for paint.
4) check all the floor panels.
5) check for leaks in upper deck (maifold). You will see them with the leaf blower if you run out of turbo boost below 15k ft.
6) make sure, as Kevin says, your turbo output is up to snuff.
7) Dirty dump valve or bad cabin controller can cause problems but you will see this with the leaf test as the system is fail save.
8) There are some "flapper" valves in the wing inlet area for fresh air that close off when pressurized. These may be sticking open.
9) Check the bulkhead feed thru's both front and rear. Loose bulkhead connectors or bad wiring installs will cause leaks. I found vacuum bulkhead connectors lose causing problems.
10) Check for items that might have been pulled out and not capped such as the fuel flow tubing or partial deice plumbing that might have been removed.
11) The turbos are different on the front and rear. Make sure they have not installed the smaller turbo on the rear. Check p/n on turbos to insure they are correct.
It doesn't take a lot to lose a lot of air at 3.3 PSI. It is the accumulated leaks that begin to add up. I can almost guarantee all the cable seals (item 2) are history. They are different sizes so be careful when you order.
you didn't give us the year or s/n as GMAS would say.......
It is a long tedeous process to tighten up P ship. I have even seen rivits leaking would you believe! As previous board member commented "there is 20 lbs of sealant in this "dude".
I am sure others will chip in.
GMAS... you have been quiet...
Bob
|