Fuel Pressure Issue EFII

[dmattmul]

I now how 35 hours in my RV14A with the IO-390. First 32 hours were perfect and the EFII system (Fuel Injection and EI) has been great, very very smooth. Starting a few hours ago instead of seeing a slight decrease in fuel pressure (28.7 in. mp and 42 psi) at I take off and slight decline when in cruise (22.0 in. mp and 39 psi) and now seeing at take-off 29 psi and 34 psi in cruise. Idle still around 40 psi. I have not contacted EFII yet and will try tomorrow. (Robert has been extremely helpful this last 3 years during the build and engine run-up) Checked the fuel flow and it's ~ 50 GPM ok. (35 GPM min.). Seems the filters must be ok. (It has a pre-pump filter and a post pump filter) The regulator is plumbed per instructions and the mp line to the regulator appears to be fine. Any suggestions?

[TS Flightlines]

Dwight---verify that the pressure has actually decreased and not an electronics anomoly.

Tom

[rocketman1988]

Did Robert tell you to set 42 psi?

I set mine up per the instructions at 35 psi static which is about 28 psi while running. I actually called him to verify 35 psi static and not while running....

[dmattmul]

35 psi is the correct set point. It worked quite well at 42 psi so right or wrong left it there. I’ll don’t think that is the issue but will ask Robert. Issue might be self inflicted but won’t be the last.

[Toobuilder]

Just a data point, but my SDS system is set to 49 and does not move more than a few PSI regardless of fuel type (100 LL or regular unleaded), OAT or power setting. SDS fuel module, Borla regulator. Bulletproof.

[smt6]

Originally Posted by Toobuilder

Just a data point, but my SDS system is set to 49 and does not move more than a few PSI regardless of fuel type (100 LL or regular unleaded), OAT or power setting. SDS fuel module, Borla regulator. Bulletproof.

Just a data point, but my EFII system is set to 35 and does not move more than a few PSI regardless of fuel type (100 LL or regular unleaded), OAT or power setting. Bulletproof. USA company!

[dmattmul]

Using a G3X EFIS and G3X-FUEL-PRESS-INJ-02 sender if that helps.

[Ralph Inkster]

Maybe disconnect & plug the MAP line at the regulator. Take it for a test flight & see if it holds constant pressure. This might shed some light on the MAP input.

[rcpaisley]

We set the static fuel pressure to 35psi (engine off, one pump running).
If you ever had a leak in the fuel rail, this minimizes the volume of fuel leaked.
Fuel pressure is manifold pressure referenced. I.E. it goes up and down with manifold pressure. This function is driven by the manifold pressure line that is connected to the fuel pressure regulator.
The normal operating fuel pressure is 35psi at high manifold pressure to approx. 25 psi at the lowest manifold pressure.
This function can easily be tested without running the engine if there is a question of how it is operating. You can get a $20 Mighty Vac hand vacuum pump at the auto parts store (breaker bleeder kit). Attach the hand vacuum pump to the pressure port of the regulator. Now you can simulate all manifold pressures and run the regulator through it's full operating range.

Fuel pressure sender anomalies are common. If there is any question about your fuel pressure reading, it is always a good check to test the fuel rail pressure with a mechanical gauge and make sure your engine monitor agrees with the mechanical gauge.

Fuel pressure senders can be affected by vibration, sensor grounding (on one wire senders), and wiring.

Robert
EFII

[dmattmul]

OK, seems I need to do a little more work and check my install. This could be anything from FP sender error to avionics interference to who knows what. That is what we experimental builders do to troubleshoot our airframes and make us better builders. Let's all learn from my experience/errors.