Fuel Injection Fuel Pressure

[RV7A Flyer]

What kind of transducer? The VDOs are s**t. Replaced mine with Kavlicos, no issues, rock steady.

[DanH]

Originally Posted by E-17B

Came across this thread while looking for guidance on high fuel pressure I'm seeing on my RV-8, IO-360-A1B6D. I've had it about a year, and the GRT EFIS and EIS most often are reading way over the 45 psi limit in Lyc manuals, often 50-60. Engine runs fine, it seems, but does take a lot of leaning to bring FF in cruise to book reference fuel flows, and it seems to need a lot of leaning on ground. As I say, operation seems ok, but concerned. I'm wondering if pressure sensor is in wrong place in system? Any ideas would be appreciated.

Bill, offhand I can think of no mechanical problem that would result in high fuel pressure with the electric pump off.

A pressure transducer problem is possible, but usually they fail low and erratic.

Sounds like you purchased your RV-8. Be aware that the GRT EIS has no dedicated fuel pressure input. The fuel pressure transducer is connected to one of four AUX (general use) inputs, then the system is calibrated by entering "scale factor" and "offset" values. You may wish to check your settings, and perhaps the resistor value. Full information in the EIS user manual, and here:

http://www.grtavionics.com/documents/EIS/VDO_LowP.pdf

http://www.grtavionics.com/documents...ux%20Input.pdf

You did not mention which fuel injection system you have, but be aware that 50~60 psi, if you actually have it, is not a big deal for both AFP and Bendix/Precision systems. The dual diaphragm regulator works based on relative pressure across a main jet pressure drop, not input pressure. Either system will tolerate 80~90 psi...actually up to the limit of the internal seals. The manufacturer's legal limit is in the manuals. I'm not saying you should skip checking or correcting, just that it ain't gonna fall out of the sky while you do.

[TS Flightlines]

My .02 worth is to verify with a known accurate mechanical guage, and compare the pressure readings. MANY pressure fluxuations have been sensor issues, and not and actual pressure loss.
Tom

[rzbill]

Originally Posted by TS Flightlines

My .02 worth is to verify with a known accurate mechanical guage, and compare the pressure readings. MANY pressure fluxuations have been sensor issues, and not and actual pressure loss.
Tom

I had to do this right at the last, just before starting phase 1. It helped me discover I had mismatched resistor values and VDO sensors from the GRT sheets Dan provided links for.

Also had a VDO sensor fail (the numbers went whacko) as others have already said.

[E-17B]

Thanks! I knew I would get good info here. I also couldn't see how the real pressure could be that high. Doing fuel inj set up on Continentals at the moment, will rig Gage's afterward to verify the indications. I'm ordering a bunch of UMA steam gages to install this winter, I think I'll add FP to the rest of the order. Not a glass fan in light a/c, especially.

[Josef]

hi there,
am having problems with the fuel pressure indications of my IO-360-M1B. Am using the Dynon EMS120 with he Kavlico 50 sensor. Fuel pressure I take from the port at the Silverhawk injector. Fuel pressure fluctuates between 10 and 34 psi during flight. Have exchanged the pressure sensor as I thought the sensor might be defect, but the problem remains with the new sensor. The engine does not show any symptoms, runs smooth at any of the indicated pressure at high power at take off and low power cruise. Does anyone have an idea what the problem might be ? Could it be vapor lock in the fuel pressure line connected to the sensor ?

best regards,

Josef / RV8-A

[Josef]

hi everyone,
thanks a lot for the numerous replies and advice regarding my problem
with the fluctuating fuel pressure on my YIO-360-M1B engine. Actually I
have solved the problem now. The cause for the fluctuating fuel pressure
indication was VAPOR LOCK in the fuel pressure hose. I have connected
the fuel pressure hose to the silverhawk injector which is located at
the front lower end of the engine. The fuel pressure hose I have routed
underneath cylinder 1 and cylinder 3 back to the firewall where the
pressure sensor is located. It seems that the fuel in the pressure hose
got heated up during longer flights at higher levels - thus causing
vapor locks in the hose and thus causing the erratic readings of the
fuel pressure. I have put an additional heat protection sleeve on the
fuel pressure hose now and re-routed it as far away as possible from the
hot areas near the exhaust pipes of cylinder 1 and 3. Problem solved, no
more erratic fuel pressure readings. Now I have one perfectly good
Kavlico 50 fuel pressure sensor as spare...

best regards,

Josef