Change in fuel pressure

[ohdub]

I have had my J for 8 months now and fuel pressure used to sit somewhere in the bottom of the green arc - around 17-20 psi.  But for the last few weeks it is up around the the top of the green arc - around 27-29 psi and if I turn the boost pump on it hits the red line. Is this an indication of something going wrong? On the one hand it's in the green so that should be ok, but it is a rather large and sudden change which has me concerned.

Thanks

[Guest]

Seldom do fuel fuel pumps fail and increase their output pressure.  More likely it's an indication problem.  You can confirm with a test gauge.

Clarence

[ohdub]

Thanks Clarence. Would you say it's safe for me to wait until I bring it to you in January for its annual?

[Yetti]

Have you checked the servo screen?

[Piloto]

Mine reads high exactly the same way. Curiously when there is no fuel pressure it reads some low pressure some times. You can check the fuel system for leaks with the following test:

1. Engine off

2. Throttle and mixture open (full forward)

3. Turn electric fuel pump for pressure indication

4. With the pump running close mixture and throttle (fully aft)

5. Turn pump off.

Watch the pressure gauge. If the pressure drops within a minute you have a leak. If the pressure holds your system is OK. If the engine pump diaphragm is cracked you will see fuel coming out of the pump breather line.

José

[ohdub]

I'll try that, thanks.

 

[BobAustin]

Jose,

Would your pressure test work on my Cont IO550A in my Missile ?

 Have low indicated fuel pressure after replacing all fuel pumps with overhauled units.  Scary but runs and flies just fine.

Bob

 

[toto]

Hi @ohdub, did you ever resolve this question?  Did you end up waiting to annual?

I had nearly identical symptoms on my last flight - fuel pressure was at top of the green, but would go into the red with boost on.  Carefully watching fuel flow, perhaps out of paranoia, I was seeing consistent but not rock-solid flow, varying no more than 0.2gph.  The engine seemed perfectly happy.

I'm trying to decide whether it should go into the shop for fuel screen inspection before my next flight, or whether this is something that can safely be watched for a while.

[ohdub]

On 2017-05-24 at 0:11 AM, toto said:

Hi @ohdub, did you ever resolve this question?  Did you end up waiting to annual?

I had nearly identical symptoms on my last flight - fuel pressure was at top of the green, but would go into the red with boost on.  Carefully watching fuel flow, perhaps out of paranoia, I was seeing consistent but not rock-solid flow, varying no more than 0.2gph.  The engine seemed perfectly happy.

I'm trying to decide whether it should go into the shop for fuel screen inspection before my next flight, or whether this is something that can safely be watched for a while.

Oddly enough, I had forgotten about this. My fuel pressure readings have remained consistent ever since and I completely forgot about it when the annual came around, so I didn't have it checked.