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Manifold pressure gauges keep dieing

A

agent4573

Well Known Member
Full g3x system, gea24, all Garmin sensors. Coming up on the 2nd annual and my 2nd manifold pressure gauge is on its way out. If the manifold pressure is less than 10-12", the g3x gauge goes to zero. If it stays there long enough I'll get a red x which goes away when the throttle gets pushed back up. It normally seems to be accurate when the MAP is 20" or higher, but today I was doing stalls and noticed the g3x was reading 15" while both my SDS gauges were reading 25". This is the 2nd time this has happened, and the first time I replaced the sensor and checked all the lines and connections for an air right seal. I didn't find any leaks or damage and the problem seemed to go away for a few months after replacing the sensor.

I run a 3an line off cylinder 4 to the Vans provided firewall sensor tree. The restrictor elbow is mounted on the bottom of the tree. The sensor is on the top. Is having the restrictor that close to the sensor killing the sensors? I would really like to solve this one at annual later this month.
 
agent4573 said:
Full g3x system, gea24, all Garmin sensors. Coming up on the 2nd annual and my 2nd manifold pressure gauge is on its way out. If the manifold pressure is less than 10-12", the g3x gauge goes to zero. If it stays there long enough I'll get a red x which goes away when the throttle gets pushed back up. It normally seems to be accurate when the MAP is 20" or higher, but today I was doing stalls and noticed the g3x was reading 15" while both my SDS gauges were reading 25". This is the 2nd time this has happened, and the first time I replaced the sensor and checked all the lines and connections for an air right seal. I didn't find any leaks or damage and the problem seemed to go away for a few months after replacing the sensor.

I run a 3an line off cylinder 4 to the Vans provided firewall sensor tree. The restrictor elbow is mounted on the bottom of the tree. The sensor is on the top. Is having the restrictor that close to the sensor killing the sensors? I would really like to solve this one at annual later this month.
Click to expand...
My MP sensor died at about 390 hours. Fortunately, it is an easy replacement because the wires are in a plug. No rewiring required! 🤗
 
Your G3X system supports many different manifold pressure sensors, produced by various manufacturers... which one do you have installed?
 
mburch said:
Your G3X system supports many different manifold pressure sensors, produced by various manufacturers... which one do you have installed?
Click to expand...
  • 494-30004-01 Manifold Pressure, 30 PSIA, 1/8-27 NPT
It's the Garmin labelled P4055 sensor. The original came in the 4 cylinder Garmin EIS bundle. The 2nd was an aircraft spruce replacement based on the part number above that's advertised as a Garmin part. The one I buy next might not be a Garmin part though if there's a better option out there.

www.aircraftspruce.com

Garmin G3X Manifold Pressure 30 Psia Sensor Kit | Aircraft Spruce

Garmin G3X Manifold Pressure 30 Psia Sensor Kit Garmin G3X Manifold Pressure 30 PSIA 1/8-27 NPT Sensor Kit.
www.aircraftspruce.com www.aircraftspruce.com
 
agent4573 said:
  • 494-30004-01 Manifold Pressure, 30 PSIA, 1/8-27 NPT
It's the Garmin labelled P4055 sensor. The original came in the 4 cylinder Garmin EIS bundle. The 2nd was an aircraft spruce replacement based on the part number above that's advertised as a Garmin part. The one I buy next might not be a Garmin part though if there's a better option out there.
Click to expand...
I haven't heard of the Kavlico P4055 manifold pressure sensors having too many problems; I have one in my airplane. According to Table 21-1 in the current G3X installation manual (revision AU) there are other ones you could try, such as this.
 
Is the line leading up to the sensor going uphill to prevent fuel and liquid from migrating down the line and into the sensor? I’ve seen dye from the fuel get into the line… also how is the sensor attached? Cushion clamp? Prop balanced to remove vibrations?
 
This shows the routing. The stainless line comes off cylinder 4. Run mostly level for ~6 inches, then heads uphill to the sensor tree on the firewall. The 45 degree fitting that it attaches to in the sensor tree is the vans VA-128 restrictor fitting with a 40 thou hole. Both the fuel and oil sensor are mounted on the sensor tree and neither of them have given me any problems.

Prop is balanced, I think I stopped around 0.06 IPS which isn't perfect, but is well withing the tolerance for a "good" balance.
 

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