PA-28 Fuel Pressure

[Victorian]

Going back to 2013:

The problem went away after changing both (perfectly serviceable) electric and mechanical pumps. It was never explained, and has not recurred in 1000 hours flying since. My opinion is that the PA 28 fuel system is fundamentally flawed from design onwards and susceptible to minor variations in component behaviour.

My further opinion is that there are many engine failure incidents in PA28’s where a conveniently undetectable cause (carb icing) is attributed when the actual cause is never identified. I’ve never seen the slightest suggestion of carb ice in best part of 2000 Hrs of PA28-161.

I should say say that my loss of pressure never went anywhere the 0.5 psi minimum and certainly didn’t cause any sphincter puckering. But it is something you notice during a long sea crossing!

[Ebbie 2003]

I saw this in my Archer II late last year, pressure on the mechanical pump dropped to about half its normal position. Applied the electru0ic pump and it went to normal, after a minute ir so, electric pump off and it stayed in the normal position - never happened since. Was at 6,500 half way direct Barbados to Canefield, Dominica, 2,200 rpm, 14C OAT, full tanks at Barbados, so likely maybe 40 gallons at the point I saw the "problem".

[jmmoric]

Yeah, happens in our PA28 from time to time as well, rarely though.

I see it as one of the oddities of a mechanical clock... so as long as it stays in the green, and engine is not loosing power or cylinder temperature is not changing.... I'm happy.

I'm one of the scanning guys.... even do it in my car now.... damn training.... ruined the relaxation of driving.

[B2N2]

Being an electric gauge and a $2 one at that I’d be suspicious of a bad ground or a bad wire somewhere.
Especially after MX or an engine swap or rebuild or gauge replacement.
Easy to nick a 40 year old wire somewhere.

[Victorian]

Originally Posted by B2N2

Being an electric gauge .

If it was an electric gauge I'd be with you 100%. But it isn't, it's mechanical. And it's continued working OK for 8 yrs and 1000 Hrs to date.

[B2N2]

Originally Posted by Victorian

If it was an electric gauge I'd be with you 100%. But it isn't, it's mechanical. And it's continued working OK for 8 yrs and 1000 Hrs to date.

Its one of those where the fuel line actually runs into the cockpit through the firewall?



( Can’t remember the specifics of the PA28)

[Pilot DAR]

I had a progressively lowering fuel pressure on my O-360. After a lot of troubleshooting, it turned out to be a failing sender. The senders are not intended to be mounted hard to anything that vibrates (like and engine), they wear. They should be remoted to a non/less vibrating mounting with a flex line. I found when I disassembled my failing sender, the wiper which runs on the rheostat wire coil had worn so much that it had a much large effective contact width, and it shorted out a number of the rheostat wires, causing a reading which was false, and changing as the wiper wore more. It would still make an electrical connection, and send the signal for a pressure, but it was inconsistent and wrong.

Try changing out the sender. If you can mount it remotely, that will help preserve it.