|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

10-16-2013, 09:08 AM
|
 |
|
|
Join Date: Mar 2009
Location: Netherlands
Posts: 663
|
|
Low fuel pressure
Before I open the fuel system once more I hope someone will come with a solution/things to check.
A few flights ago I had one drop of fuel pressure during cruise. Pressure dropped from 4,5 to 0,7, lasting 10 seconds. Pressure recovered in a few minutes. During the climb out after a low pass 10 minutes later the pressure dropped to 0,2psi. Rest of the flight normal values. All flights before I had a constant pressure of 4,5 in all flight phases.
I changed the fuel pump (still had the old one, not leaking) and replaced the sensor for a "Kavlico" sensor.
Test run thereafter didn't show any problems, steady pressure around 4,5 with both the electrical and mechanical pump, 4 with only the mechanical (engine off pressure is around 2,5).
During the flight thereafter I had a pressure drop during climb out to 0,2 , lasting 20 sec. Pressure climbed back slowly up to 5 psi after 45 minutes flight. The flight thereafter on the same day gave me a minimum pressure of 2,5 during climb out, normal pressures for the remainder of the flight.
Last flights the same problem; first flight very low pressure, flights thereafter on the same day no problems.
I checked the gascolator, totally clean, and did an other flow test. Flushed all fuel lines after the gascolator (bit redish fuel from the pressure line).
Fuel flow values are constant during the pressure drops, engine is running fine. Pressure drops occurs after giving power. In case of pressure drops due to supply problems I expect to see fuel flow will drop as well but I don't see that.
I forgot to download the last flight, will post that next week.
-Next step will be a mechanical gauge to check the digital values.
-Checking the finger screen in the tank
-checking the fuel valve
Any more suggestions?
|

10-16-2013, 12:31 PM
|
 |
|
|
Join Date: Aug 2010
Location: Marshall TX (KASL)
Posts: 1,783
|
|
I would purge/blow the line to the sensor (not just drain it) before opening the tank. Any restriction, debris, or possible intermittent kink might cause these symptoms.
I use all mogas. I have a 15 gal hangar container with a handcrank pump on it. I fill that container with jerry-canned gas. Whenever I pour into the container I use a Mr. Funnel to ward off debris. (Pretty awkward to lift a 5 gal container up to the fueling port.)
|

10-16-2013, 04:10 PM
|
|
|
|
Join Date: Feb 2009
Location: Mittagong NSW Australia
Posts: 7
|
|
I had 2 Kavlico fuel pressure senders fail so far.The first one showed zero pressure after being installed for 5 hours,the other one became very erratic with having fuel pressure low and high alarms after a few hours in service.
Seems they are not as reliable as presumed.....or just my bad luck?
cheers
Karl VH-XKH 11Hours total
|

10-16-2013, 06:31 PM
|
|
|
|
Join Date: Sep 2013
Location: Tucson, AZ
Posts: 322
|
|
I would bet it is a poor wire connection or a bad sending unit. These two causes are 96% of the erratic low pressure issues.
The only real way to double check is put a mechanical gauge inline with the other.
__________________
Roger Lee
Tucson, AZ
|

10-16-2013, 08:05 PM
|
|
|
|
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
|
|
Joeri,
Did you experience any loss of power? A lot will disagree with me, but I've flown plenty of airplanes that had no fuel pressure gage. If you lose pressure you react to the loss of power. The number of false alarms reported in this forum seem to indicate the fuel pressure reading is not a reliable troubleshooting indication. Having said that I should point out that I put a switch on my electric pump and only turn it on for start, takeoff and landing so I have a 'plan B' if the engine sputters.
Rich
|

10-16-2013, 08:17 PM
|
|
|
|
Join Date: Jun 2009
Location: Dayton, OH
Posts: 838
|
|
Fuel Pump switch????
Rich, I'm thinking of putting a switch on the electric pump at the CI next week, but if you cit the red wire in the tunnel as described elsewhere, does that also shut off the avionics cooling fans? Don't want to do that around here in the summer!!
Wayne 120241/143WM
|

10-16-2013, 08:40 PM
|
|
|
|
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
|
|
No, power flows back to the fuel pump through the red wire. The Avionics fans tap in at the control panel so cutting the red wire won't impact the fans. I'm happy with the mod powering the fuel pump through the unused Nav light switch.
Rich
|

10-16-2013, 11:26 PM
|
|
|
|
Join Date: Oct 2009
Location: Canby, OR
Posts: 53
|
|
Check/Rewire connections.
If you have tried two senders, it is probably a wiring issue. Check, or even re-do, the power, ground and signal connections on the sensor and monitor. Also look for any splices in any of the wires and check/re-do those. You can try wiggling the wires with the power and pump on a see if you can get it to fail.
If your pressure really drops to .2 PSI you will notice . . .
|

10-17-2013, 01:14 AM
|
 |
|
|
Join Date: Mar 2009
Location: Netherlands
Posts: 663
|
|
Thanks all.
The engine didn't sputter at any time.
Will try the mechanical gauge first and will connect the Kavlico direct to the EMS instead of the firewall forward connector.
Quote:
Originally Posted by Bill_H
I would purge/blow the line to the sensor (not just drain it)
|
I did disconnect the sensor/fuel return line and used compressed air to blow the line.
Quote:
Originally Posted by RFSchaller
Joeri,
Did you experience any loss of power? A lot will disagree with me, but I've flown plenty of airplanes that had no fuel pressure gage. Having said that I should point out that I put a switch on my electric pump.
Rich
|
No loss off power/no sputter, fuel flow indication was constant during all fuel pressure losses. I also have a switch on my electric pump.
The Katana flown for the transition training had also no fuel pressure indication (only a fuel pressure caution light).
|

10-18-2013, 12:13 PM
|
 |
|
|
Join Date: Mar 2009
Location: Netherlands
Posts: 663
|
|
A small piece of the graph from the flight I was talking about. First 0 psi indication at 600ft. Fuel flow stable. No drop in power. Third time in a row that I had these values during a first flight of the day. Still have to order a mechanical gauge.

|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 09:16 AM.
|