What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

YIO-360-M1B high fuel pressure

S

seattleworm

Well Known Member
Sponsor
I am about 18 hrs into phase 1, over all it went well. During today's flight, the high fuel pressure concern me. Engine is lycoming YIO-360, fuel pressure sensor came with the Dynon EMS sensor kit. In first few hour, the pressure range was betwwen 25-30 psi. At about 5 hours, the pressure can sometimes jump to 35psi, triggering alarm. Today, the pressure intermittently jumped to 45 psi (or maybe higher since the skyview was set to display 45psi max). Turning boost pump on didn't make much difference. The high pressure indication is intermittent, normally happened after reducing power to slow down or decend. When pressure is showing high, the reading is pretty jumpy. Sometimes opening throttle or pushing mixture to full rich will reduce the pressure a bit, but there is no definite correlation. Despite high and jumpy pressure indication, the engine continued to run smoothly. I searched the forum, and know that the other (old) sensor might have premature failure providing high and jumpy pressure reading, but I didn't see any such a report for the newer one that Dynon provides in EMS sensor kit. The search on this topic leave some action items to further check some other possible causes, but did anyone experienced the same thing on the Dynon fuel pressure sensor? I will call Dynon tomorrow to see if they can shed some light. Hope it is just the sensor, not the fuel pump.
 
Last edited:
The VDO 1 wire sensors Dynon used for oil and fuel pressure would jump to a higher pressure indication if not well grounded. Vibration would also wear the internal parts causing the same thing, would not happen in only an hour. If you have the VDO sensor, try tightening it into the manifold. Then call Dynon and order the newer 3 wires sensor. If you already have the newer 3 wire Kavlico sensors, check your ground wire.
 
Dave,

I have the Kavlico 3 wire transducer, I checked the ground and it is ok. Actually, the fuel and oil pressure sensors share the same ground wire to EMS unit. Oil pressure reading is normal and steady, so I guess it's not the ground. From all I can read, Kavlico transducer is pretty reliable because it's solid state. If so, what puzzled me is my boost pump only and engine driven fuel pump only pressure reading all increased to 44-45psi from about 28 psi in the first few hours. The chance of both pumps failing at the same time is just too rare. Haven't got a chance to talk with Dynon yet, still hope it's just a faulty transducer.
 
High pressure is not due to bad sensor

I got a new sensor from Dynon and did a test flight yesterday. Now I can say the high and fluctuating fuel pressure is not due to a bad sensor. I can't find definite correlation between the pressure fluctuation and power setting. Most of time, the pressure will stable at about 27 psi for take off and clime, then after reducing power, the pressure will start doing its own thing. However, there are times that the pressure is jumpy at the beginning. In all cases, the engine ran smoothly. If not due to the pressure reading, I wouldn't notice anything.

I know some people have reduced pressure due to vapor in the fuel line, but in my situation, the pressure kept increasing. Is it the fuel pump? Hard to believe the pump is bad after only a few hours. Also, if the pressure really jumped around like that, shouldn't I notice anything from engine performance, like jumpy fuel flow?

Really need help here!

[Top chart showing fuel pressure and Fuel flow, bottom chart showing RPM and MAP]

Fuel pressure with Pwr Setting for second flight, looks pretty good
2ai0c1y.jpg


Fuel pressure jumpy at the beginning of the flight
33lgmea.jpg


Constant pwr setting, pressure gradual increase
2i70jkw.jpg


After installing a new sensor
29mu9hk.jpg
 
Last edited:
How do you know the sensor and related systems are reporting the pressure properly? I had an pressure issue in Phase 1 but like you it was unknown whether it was real or an indication issue. I plumbed in a new mechanical dial gage for comparison and pressurized the system with the boost pump.
Different indications. I found I used the wrong resistor value in the wiring harness. Sensor was fine. New resistor. Fixed.

Similarly, some of my sensors were driven with regulated power from the EIS4000. They were pretty squirrelly until I found a bad crimp in the +V harness.
 
Last edited:
Bill, good thought. In my setup, Since my oil pressure indication is steady, I will plug the harness for oil pressure sensor to fuel pressure sensor (the connectors are the same), and re-config my skyview to see if the fluctuation is due to some bad connection from sensor to EMS module. Will report back what I found.
 
If you have Bendix or similar FI you can?t have high fuel pressure, the pressure is set by the strength of the spring in the mechanical pump, that spring is not going to gain strength.
 
Russ, yes. I have read a lot of articles about fuel pump and fuel injection system in the effort to solve this mysterious pressure fluctuation. Yes, from what I read, the diaphragm mechanical pump can't pump more pressure than the spring set value if the crankcase is well vent ( which I checked to be sure). After reading about how precision fuel injection system works, I would think any fluctuation in unmetered fuel pressure, which is the pressure monitored by EMS, will result fuel flow change as well. But my fuel flow didn't show that correlation.

Just went to my hangar checked the harness for fuel pressure sensor, it looks fine. I swapped the fuel and oil pressure harness, nothing unnormal. And shakes the wire bundles connecting pressure sensor to EMS module with fuel line pressurized, didn't get jumpy reading. Also, the oil and fuel pressure sensors share the same power and ground wires. I may conclude that there is no bad connection between sensor and EMS module.

So it is unlikely I got a bad pump and a bad sensor. Thinking I might have some air trapped in the fuel pressure line, I purged the line today. Will check if this will make any difference during next test flight. Hate to take the fuel pump out before all other possibilities are exhausted. What else do I need to check? Or just live with it as long as the pressure will not go down?
 
Shawn, I have no magic or weird trick here, but would second the thought of putting in a mechanical gage for a bit just to compare. This would be easier than trying to remove a pump and would give solid assurance of sensing vs pumps to continue narrowing it down. Just a thought.
 
Not the fuel pump

The high pressure pump on the Lycoming engines have a internal spring on the diaphram which limits the max pressure the pump can put out which is around 26 psi. Therefore if you are reading high pressure beyond 26 psi with only the engine pump running then it is not the pump.

Sounds like a power supply or EMS issue if the wiring is sound.

I have the VDO senders which developed an offset over 200 hrs and a friend had high pressure reading with his system. Replacing the senders solved the problem.
 
seattleworm said:
Just went to my hangar checked the harness for fuel pressure sensor, it looks fine. I swapped the fuel and oil pressure harness, nothing unnormal. And shakes the wire bundles connecting pressure sensor to EMS module with fuel line pressurized, didn't get jumpy reading. Also, the oil and fuel pressure sensors share the same power and ground wires. I may conclude that there is no bad connection between sensor and EMS module.
Click to expand...

Well....... I had to completely disassemble a roughly 1/2 inch diameter harness near a D-sub to get to the specific splice before I found that the fuel pressure +V pulled out of the splice but the other wires in the same splice were crimped solid. I had already done the shake and touch routine to no avail.

It was a matter of logic to decide where to pull the harness apart. Basically went upstream until I got to a common connection that drove a working system (other sensors).
 
It might be a faulty fuel pump

I talked with Lycoming Tech Support today, they think it's faulty engine driven fuel pump with sticky pressure relief. I will file a warranty claim and have the pump replaced. I still don't believe the pump can be bad within such a short time, but they said it's a simple pump, and have seen similar situation before. I will report back the results once I got the pump replaced. I guess I will be grounded for a while :(
 
fuel pressure fluctuations

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
 
problem solved...

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
 
You must log in or register to reply here.
Back
Top