I can’t speak to the Arrow, but the pressure gauge on my Warrior is mechanical and started to show 1/4, rather than 1/2, scale deflection in flight. The 1/2 scale reading was always restored by application of the electric pump. It took replacement of both electric and engine driven pumps to rectify the situation, although neither of these appeared faulty on their own. It seems to me that the PA-28 fuel system design is fairly marginal and that only a small restriction or something can give strange readings. This is confirmed by the POH which quotes (from memory) a ludicrously small 0.5 psi as the minimum acceptable.
Yep, ours is an Arrow and fuel-injected. Wonder if that means the Fuel Pressure Gauge is electrically driven and manometer only on carburettor versions of PA28’s ??!!
There was quite a lot of work involved to get the cluster out for cleaning the meter (half a day). I think the small copper pipe is connected to the carburettor, so maybe it is easier to measure fuel pressure there with a different gauge?
Thought the Arrow was fuel-injected?
G
Think I’ll just feel behind the gauge (panel) and see if the gauge has a hard capilary tube connected to it.
Sure ther will be at least one wire there for the back lighting.
This one was 1973 PA28-180
You could look in the part catalog or another manual, I guess.
G
GaryStorm. That’s very interesting. So our gauge could be electrical OR manometer (direct fuel pressure). Need to check that out.
What year is your PA28 ?
On my PA28 that instrument has fuel connected via a copper line. Thus, the instrument is a manometer and not an electrical instrument. Sometimes gunk clogges the tiny hole that leads fuel into the instrument, leading to strange readings.
After clearing the very small hole with a thin sharp object and some parts cleaner, readings were fine again.
G
I understand the gauge is electrical driven from guess a voltage / current variation generated by the ‘sender unit’. Which in turn is connected direct to the fuel line, thus detecting actual pressure.
Put a calibrated pressure gauge on the line to verify the accuracy of the gauge reading.
On our PA28R-200, (Arrow II) it still happily in the middle of the green.
If it’s been like that for years, then I’d not panic and refuse to fly immediately, but I would want to get it fixed sooner rather than later. Otherwise the day that there is something wrong with the fuel pressure, how do you know about it (before the engine stops).
