High Fuel Pressure Warning!!!! HELP!!!

[nice1111]

Hi All,

Ive been have high fuel pressure warnings on my D180. i have tried everything from Checking connections, ground etc, d180 settings and finally getting a new sender. Tomorrow i have a guy coming round to check the fuel pressure, to see if i actually do have high fuel press.

When i start up engine (rotax 912)the mess flashes up and gives me a reading of about 0.45bar (see pic). usally about 10mins into the flight the pressure returns to normal.

ive been onto rotax in the uk and well im still no better off.

I have noticed that when the engine is switched off the fuel guage reads 0.15 and with the two wires taken off the fuel sender, the guage reads 7.20 bar. IS THIS NORMAL!!!!????

 

[dynonsupport]

What sensor type are you using (under SETUP>SENSOR>FUEL PRESSURE), and what does the marking on the sensor itself say? (either 0-2, 0-5, or 0-10 bar).

 

[himslv]

What follows is what I sent to the RV8 list.  In short remove the tabs that came with the VDO fuel pressure sensor and use standard (hole) crimp connectors.

Hello,

This is followup to my inquiry about erratic high fuel pressure readings on my Dynon supplied VDO fuel pressure sender.

To recap, I would have normal readings for about thirty minutes then my fuel pressure would slowly creep up to 9 or 10 psi, then start bouncing around tripping my warning alarms (wakes you up quick).

I do not have fuel injection but in my archive and google search came across those with the same problem only with higher PSI readings.

Well, skipping the "I did everything perfect part", the VDO fuel pressure sensor comes from Dynon with mounting tabs already installed. You assume as I that these tabs are a match for the aircraft quality slide on crimps. They apparently are not.

I removed and tossed these tabs and used a standard crimp connector instead (one with hole in it). Fuel pressure readings are now rock solid after two hour flight. Keep the nut and washers for use with the standard crimp though (I think they're metric) and do not tighten too much as I/you don't know if too tight will change the sensor resistance.

In my troubleshooting odyssey I used a scope meter (yes I got that desperate) to determine if any electronic device save the ignition was affecting the signal. The signal stayed rock solid. The radio would impress a millivolt high frequency signal across the sensor but there was no affect on the voltage or displayed PSI.

My take on the problem is that the tab crimp interface due to the mismatch would become intermittent when exposed to heat and/or vibration.

I relay all this to help others avert a very long, frustrating search. Frustrating in that most of us won't fly with erratic fuel pressure readings.

...hope this helps!

 

[N8RV]

I, too, had a high fuel pressure warning last weekend. IO-360 in an RV-8, and the normal fuel pressure runs in the mid-twenties. However, I happened to see the fuel pressure rise to 30 psi, then continue a very slow climb where it maxed out at around 36. Everything else seemed quite normal with the engine readings, so I just watched it.

I flew for 2 hours yesterday to see if the problem persisted. Nope. Rock solid at 26.6 psi.

Any clue why it would show a high reading like that and then suddenly return to normal?

 

[dynonsupport]

The fuel pressure sender increases in resistance for an increase in pressure. This also means a loose wire or ground connection will show higher pressure than is real.

I'd triple check all your connections and ground paths. My assumption would be that you have something becoming loose. The change from 27 to 37 PSI is only about 10 ohms (assuming you are using the 80 PSI sender)