High Fuel Pressure Reading

[0TreeLemur]

I have a J model with a JPI EDM900 installed.  Lately after startup the fuel pressure has been indicating over 30 psi.  With or without boost pump on.   During runup it sometimes indicates  above 30.   After takeoff, it indicates 27-28 psi.

It seems unlikely that an engine driven fuel pump is going to go over max. rated pressure at any engine speed < redline.   Suspect a transducer problem.   Anybody dealt with this?  I'm not worried about it- I just don't like it.  Anyone got a working spare they'll part with?  The part is made by Kavlico, with 0-30 range outputting 50mV at 30psi.

EDIT: Added screencap of JPI data.   The red line is MAP, light blue line is FP.   You can see after I took off, it went back down into the normal range.  Had a time mid-flight there were FP was pretty noisy.

 

[RoundTwo]

I’ll usually look for a bad ground when flaky readings present themselves. Can you “T” the line for a test with an analog gauge?

[Rick Junkin]

Check the barrel connector on the transducer pigtail. It’s likely dirty/corroded. Cleaning it up may provide a short term fix. It worked on my Bravo.

There’s a service instruction from the transducer manufacturer that essentially says to replace the barrel connector with individual knife connectors on each wire. I have it filed, once I get to my computer I’ll send you a copy.

[Rick Junkin]

@0TreeLemur Found it

BENZ AIRBORNE-KULITE TRANSDUCER.pdf

[EricJ]

I don't think I've ever seen somebody suggest replacing a pinned connector with handshake terminals before.

[N201MKTurbo]

56 minutes ago, EricJ said:

I don't think I've ever seen somebody suggest replacing a pinned connector with handshake terminals before.

I did it on the pressure transducer for a Saratoga landing gear. The connector was intermittent and unobtainable. Worked great afterward. They weren’t AMP CPC connectors.

[0TreeLemur]

Thanks @Rick Junkin.   I too suspect a connection issue.   Looking back through the EDM data collected during the past year, this problem has been intermittent, but increasing if frequency and severity of late.   The transducers included with my JPI use MetriPak connectors, which are "supposed" to be weather resistant.   I'll go ahead and remove the cowl and give them a look see.

[PT20J]

It’s certainly easy to open the connector and look at it. However, the CPC connectors are high quality and Mooney uses the solid machined 4-way crimp pins. I had the Kulite fuel pressure transducer fail (read zero) and verified it with resistance measurements. The EDM uses a different transducer. 

[Ragsf15e]

On 8/18/2025 at 12:15 PM, 0TreeLemur said:

I have a J model with a JPI EDM900 installed.  Lately after startup the fuel pressure has been indicating over 30 psi.  With or without boost pump on.   During runup it sometimes indicates  above 30.   After takeoff, it indicates 27-28 psi.

It seems unlikely that an engine driven fuel pump is going to go over max. rated pressure at any engine speed < redline.   Suspect a transducer problem.   Anybody dealt with this?  I'm not worried about it- I just don't like it.  Anyone got a working spare they'll part with?  The part is made by Kavlico, with 0-30 range outputting 50mV at 30psi.

EDIT: Added screencap of JPI data.   The red line is MAP, light blue line is FP.   You can see after I took off, it went back down into the normal range.  Had a time mid-flight there were FP was pretty noisy.

 

I’m surprised nobody has pointed this out, so maybe there’s something I’m missing, but this has been happening on a lot of Mooneys. I thought we traced it down to a newer style/brand fuel pump that has a tendency to hit right at the max of 30 or just above it, especially on the ground. I know my F was doing that after we replaced the fuel pump. I guess what I’m saying is it’s probably correct, and it is not a problem. The fuel servo can take something like 40 to 60 psi. I think @PT20J has the specs that the engine can actually tolerate.

[PT20J]

2 hours ago, Ragsf15e said:

I’m surprised nobody has pointed this out, so maybe there’s something I’m missing, but this has been happening on a lot of Mooneys. I thought we traced it down to a newer style/brand fuel pump that has a tendency to hit right at the max of 30 or just above it, especially on the ground. I know my F was doing that after we replaced the fuel pump. I guess what I’m saying is it’s probably correct, and it is not a problem. The fuel servo can take something like 40 to 60 psi. I think @PT20J has the specs that the engine can actually tolerate.

Al Jesmer at Precision Airmotive has stated that the RSA fuel injection servo works fine with input fuel pressures in the range of 20-35 psi. I have heard that at one point Lycoming was shipping fuel pumps that exceeded the 30 psi limit that Mooney put in the airframe limitations. However, the rebuilt IO-360-A3B6 that I got from Lycoming in late 2018 does not have this issue, so if it was a problem, Lycoming seems to have corrected it.

[Ragsf15e]

31 minutes ago, PT20J said:

Al Jesmer at Precision Airmotive has stated that the RSA fuel injection servo works fine with input fuel pressures in the range of 20-35 psi. I have heard that at one point Lycoming was shipping fuel pumps that exceeded the 30 psi limit that Mooney put in the airframe limitations. However, the rebuilt IO-360-A3B6 that I got from Lycoming in late 2018 does not have this issue, so if it was a problem, Lycoming seems to have corrected it.

I can’t exactly remember where I got my mechanical fuel pump, but it was overhauled/exchanged. Maybe through Spruce or Aircraft Accessories?  It was probably 2020, and it was always ~30-31psi on the ground - measured by an edm-930.