Flickering fuel pressure gauge.

[nigelm]

Can anyone help? I decided to drain down the tanks on my Tecnam Bravo with Rotax 912 to calibrate the fuel gauges. On finishing this work the fuel pressure gauge now flickers, it does more or less flicker between the correct pressure.

 

So thinking I must have dislodged some crud some where in the system I cleaned the fuel filter in the gascolator and also in the electric pump, there was a little residue but nothing out of the norm. I then unscrewed the fuel return pipe to the tank and blew this through with air and before refitting ran the electric fuel pump to flush from the other end, fuel came through so I presume all is well here.

 

Having done all this the gauge still flickers, has anyone any experience with this.

 

Thanks in advance guys

 

Nigel.

 

 

[Guest Maj Millard]

Nigel, It's possible you have a little bit of trapped air in the line up by the fuel-pressure guage, this will cause a pulsing. you need to try and bleed that air out somehow by loosing a fitting at the back of the guage, until you get a bit of fuel coming out then nip it up..............................................................Maj...

 

 

[old man emu]

Nigel,

 

My suggestion is teh opposite of Maj's.

 

It depends on your fuel pump type. If it is a mechanical one, then there is a change in pressure as the diaphragm goes back and forth. If the fuel pressure guage is connected directly to the pump, the pressure in the liquid in the connecting tubing will show a change in pressure as the pump strokes.

 

My suggestion is to introduce a small air bubble into the line which will act as a type of pressure accumulator and even out the preessure in the line.

 

Even though Maj and I have givien opposite solution, I think you can see that we both think that the problem is a simple one relating to the need or not to have an air bubble in the line. One of us has to be correct.

 

OME

 

 

[nigelm]

Was there some form of dampener in the line that was inadvertently lost during your work on the system? Just another thought if those above don't work out. My vacuum guages flickered so I placed dampening material in the tubes to soften the effect.

[nigelm]

Thanks guys, particularly Maj, I thought it may be air in the system, as before I drained the tanks all was OK.

 

The weather here in Andalusia at the moment is VERY HOT, if we get a slightly cooler day I am hoping next week to get up to the airfield and check things out. I will let you know how I get on.

 

Again thanks for all the post's.

 

Regards,

 

Nigel.