Fuel pressure gauge

[Seefuture]

Am struggling with a weird fuel pressure reading issue on a 1994 MSE.  On initial start up, the gauge reads perfectly but over a period of 15-20 mins will steadily drop to read zero.  This has no effect on performance (the big fan is till turning!) and the fuel flow read out is normal throughout (so we know the fuel pressure is not actually dropping). Interestingly, the drop off is quicker in the summer than the winter(?).  Re-setting the gauge breaker returns the readout to normal but it then drops off immediately  (no delay after the initial start up slow drop has occurred) to zero again. Both the gauge and the transducer (Part # APT-153-1000-30) have been bench tested by an instrument shop twice and work perfectly for hours under those conditions.  We have pin tested the harness, checked all ground/connections etc and found nothing abnormal.  There are a few posts with FP issues but nothing I have found which seems to be the same as we are struggling with.  Thoughts?  Suggestions?  Thanks in advance.

[1964-M20E]

Well my pane is 30 years older than yours and the FP gauge is mechanical.

 

However, since yours is electrical and you can only get it to present the problem in flight I would suspect that it is a temperature issue either in the gauge or the pressure sending unit (transducer) most likely the transducer since it is probably closer to the engine.  The temperature angle is why it would act up faster in the summer than in the winter.

[Piloto]

Quote: 1964-M20E

Well my pane is 30 years older than yours and the FP gauge is mechanical.

[Piloto]

Quote: 1964-M20E

Well my pane is 30 years older than yours and the FP gauge is mechanical.

However, since yours is electrical and you can only get it to present the problem in flight I would suspect that it is a temperature issue either in the gauge or the pressure sending unit (transducer) most likely the transducer since it is probably closer to the engine. The temperature angle is why it would act up faster in the summer than in the winter.

[John Pleisse]

Call me crazy...did you check the guage itself? I had this happen some years back. I vaugely recall the guage grounding out somehow. We reapired it once and bought a new one after that. Although, Jose's idea seems to jive better with the sudden drop afterreading properly.

[Seefuture]

Thanks to all for the replies.  Yes the gauge has been tested twice as well and declared good.  Interesting point re possible heat issue but we can reproduce the problem on the ground, engine running with the cowls off as well.  At this point we are growing more convinced that we have an electrical problem.  I forgot to mention that in addition to all the info in the first post, we have also noticed that the gauge only starts to drop when the charge rate drops to its normal level after initial start up.  So, when the alternator is actively “charging” the battery after the start, the gauge reads normal for a few moments then starts it’s slow drop after the battery is back up to full charge. 

[mooney2201]

i had this problem. take the sender off and shake it out on a piece of white paper,you will see particles of possible hose material, very fine ,,,,soak gage in fuel over night.than shake out as hard as you can,to remove particles,keep repeating until noting comes out of sender,,put back on, the problem should go away for a while,hose material will contaminate sender again,but will take a while...shake fitting end over paper,dirt will come out,,,hope this helps

[barbieT]

Hello everyone! Novice here. Anyway, I love planes since I was a kid. Whenever my father came home from work, he always bring maniature planes. My father was a pilot during his time that's why collecting maniature planes became part of his habit. The moment dad bring home his very first collection, that little stuff never fail to amazed me.

On the other hand, though I am very much fascinated by this planes,I also love cars and engines that's why I love reading articles pertaining to cars. One of the interesting article I've read is this article here: The basics of an engine flush, it's pretty good.

[fantom]

Barbie could not have posted the above!

She's not BLOND!

 I hate when the riff raff turns to a great site!

larry    lmao!