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  #1  
Old 05-19-2015, 07:47 AM
Darren Kerns Darren Kerns is offline
 
Join Date: Feb 2005
Location: Indiana
Posts: 163
Default AFS Manifold Pressure Gremlin

I need some help and advice. My RV7 MP reading has been acting up.

I thought my AFS transducer was going bad but when I shut the engine down it goes back up to 29 in. I turned my avionics master on last night and it indicated 3 in. I started it up and the it was showing 6 -9 in. By the time I got down to the end of the runway, it went red which means I lost it.

As soon as I firewalled it, it came back to life and indicated great the whole time while flying. My mechanic and I examined the line running back from the cylinder to the firewall. It was clean. We examine the transducer aft of the firewall and it was clean and connections were good.

I called AFS and they think it could be the transducer.

What else should I be looking at? All CHT & EGT readings are great. Engine is running strong.

I am calling AFS today to order a new transducer. Any suggestions or advice would be greatly appreciated.

Thanks,
Darren Kerns
RV7 N599DT
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  #2  
Old 05-19-2015, 08:39 AM
vic syracuse vic syracuse is online now
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Default XDUCER

Sounds like you already checked everything. Sometimes the lines will plug and cause that, but you said you checked that. I assume you did clean them out?

Vic
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  #3  
Old 05-19-2015, 08:40 AM
Tom Martin Tom Martin is offline
 
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Location: Ontario, Canada
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Check ground on the sensor
Check all electrical connections
Check the hose for leaks. A friend had his hose go bad after a few years and leaked from a number of small pinprick sized holes.
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  #4  
Old 05-19-2015, 08:55 AM
Darren Kerns Darren Kerns is offline
 
Join Date: Feb 2005
Location: Indiana
Posts: 163
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We checked the lines. They looked clean. We also tested them for leaks and did not see or hear anything. We disconnected the transducer and looked at wired ends. They looked good.

I will keep trouble shooting. Thanks guys for the help. I really appreciate it.
Darren Kerns
RV7 N599DT
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  #5  
Old 05-19-2015, 09:02 AM
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Mike S Mike S is online now
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Location: Dayton Airpark, NV A34
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Quote:
Originally Posted by Tom Martin View Post
Check ground on the sensor
Check all electrical connections
.
This is a very good place to start trouble shooting.
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  #6  
Old 05-19-2015, 09:38 AM
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Jesse Jesse is offline
 
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Location: X35 - Ocala, FL
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Disconnect the connector and see what the EFIS reads. This is the number when/if you have a bad wire. It sounds like a wiring issue to me.
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  #7  
Old 05-19-2015, 10:22 AM
Darren Kerns Darren Kerns is offline
 
Join Date: Feb 2005
Location: Indiana
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Jesse
What number are you talking about it is disconnected? I am confused.
Thanks,
Darren
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  #8  
Old 05-19-2015, 10:31 AM
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N402RH N402RH is offline
 
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It is either the wiring or the transducer.

1. Try moving the wires at the transducer and see of it fails on the screen

2. Try moving the wires at the EMS connector on the EFIS

3. Replace the Transducer


Rob Hickman
Advanced Flight Systems
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  #9  
Old 05-19-2015, 10:47 AM
Darren Kerns Darren Kerns is offline
 
Join Date: Feb 2005
Location: Indiana
Posts: 163
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Thanks Jesse and Rob
Jesse, thanks for talking to me on the phone.
Rob, I ordered a new transducer. I will try checking the wiring to see it fails.

Thanks for all the help and advice.
Darren Kerns
RV7 N599DT
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  #10  
Old 05-19-2015, 12:08 PM
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RV8Squaz RV8Squaz is offline
 
Join Date: Feb 2006
Location: Senoia, Georgia
Posts: 725
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Electrons are weird. I recently did some maintenance to my vacuum system and decided to tie wrap some wires for a slightly neater appearance. After I did that, I noticed my RPM indications were erratic (no change in actual rpm, since the sound didn't change). I rechecked the wiring and the transducer and everything appeared in order. Same erratic behavior. Someone at the hangar suggested that the ignition leads could cause interference. The wiring for the RPM transducer was adjacent to one of the right magneto's ignition leads. I went on a test flight and even with the magneto off (grounded) the same erratic behavior continued at high RPM which lead me to believe that the ignition lead was not the cause of the problem. Later I separated the transducer's wires from the ignition leads and the problem disappeared. I would have thought with no energy running through the ignition leads it couldn't affect other wiring, but it did. Electrons are weird.

Jerry Esquenazi
RV-8 N84JE
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