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Comanche Engines and Propellers
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Topic starter
07/05/2020 12:21 am
Cleaned my injectors and ?
Have 98 hrs on the twikie now since I picked it up and have been working out small issues as I go along. Pulled all the injectors and cleaned them in my profesional commercial ultrasonic machine ( I used to sell them). Can't find any where in the logs where they have been cleaned in 1000 hrs. They "looked" good but the dirt just rolled out of them as the ultrasonic worked. On the first takeoff I notice that the right side didn't go above 16 gph like it did before (dirty injectors?
, left engine showed about the same FF but seemed to control different than it did before. The mixture control seems to be less effective in a wide arc as I lean. Need more flight time to figure it out. The flow dividers have never been off so I think I will do a coke bottle test on the injector lines as soon as I can. Ran 2 hrs even on just the outboards at the same egt readings and I'll check quanities to see if flows are near each other. Got a slight difference in MP needles at FT in cruise at 12.5, Maybe 3/4 inch MP. Got to figure that one out. MP press lines were looked over at the 100 hr 2 days ago. Any ideas will be well received.

- Cliff Biggs
- Posts: 22
- Joined: Mon Dec 20, 2010 6:04 am
Re: Cleaned my injectors and ?
A Twinkie at full takeoff power near sea level should top about at about 15-16 gph IMX. Do you have a fuel flow meter that runs off a transducer or is it the factory gauge which really reads pressure off the flow divider? If the latter, cleaning the injectors could cause a reduction in indicated fuel flow.
Kristin
Kristin Winter- ICS member
- Posts: 1299
- Joined: Tue Aug 09, 2005 5:21 pm
- Location: Northern California
Re: Cleaned my injectors and ?
Factory system and that's what I was thinking, I had high FF due to dirty injectors. Proved by cleaning them. Now on to the flow divider and lines. In reading the AD on the injector lines I find mine has been done "wrong" for years so I'll be redoing someone elses work to get it correct. I'm one of the crazy A&Ps that actually reads all of the AD to see how it should be done. I just love coming in behind others on aircraft maintenance 

- Cliff Biggs
- Posts: 22
- Joined: Mon Dec 20, 2010 6:04 am
Re: Cleaned my injectors and ?
Keeps you off the streets at night doesn't it? 

Pat
Patricia Jayne (Pat) Keefer ICS 08899
PA-39 #10 Texas
N3322G- ICS member
- Posts: 1911
- Joined: Thu May 08, 2008 1:58 pm
- Location: Fort Worth, Texas area
Re: Cleaned my injectors and ?
After flying several hours I find I can go LOP and still be smooth. Something I couldn't do before. FFs right around 15 -16gph on takeoff. Shadin system maybe. Still have to change the engine mounts and look at 3 of the 4 mags. The seats are being recovered right now (Airtex kit) and I'm pulling the left boost pump next week,when I get back from the annual on the MU2, as it's showing a drip out the vent line. Pump to motor seal has gone and probably washed out the bottom bearing. All in all though it's been a great airplane since purchased and was well cared for by the previous owner considering everything. Did a manual WAAS approach last week and what a nice joy it was. Older 430 upgraded to WAAS and it went perfect.
- Cliff Biggs
- Posts: 22
- Joined: Mon Dec 20, 2010 6:04 am
Re: Cleaned my injectors and ?
Can't help but agree on the 430W box. They make even partial panel really simple.
Don
- 9089P
- ICS member
- Posts: 426
- Joined: Wed Jan 07, 2004 7:01 am