engine driven fuel pump gone bad?

[vic syracuse]

Your symptoms area also indicative of a slight leak upstream of the fuel pump, usually at the fuel selector or another fitting. Put a wrench on all of them and make sure the fuel selector is tight if it is one of the original brass valves.

Vic

[Machsandy]

Hello Vic

Please can you expand on ?make sure the fuel selector is tight?

[togaflyer]

Thanks I will go over the entire system. Can a pump have a partial failure, i.e. pressure loss during a full power climb out.

[Bill.Peyton]

Rich,
I have had similar issues in the past. The first time it happened was in level flight. Fuel pressure dropped several times in cruise flight. Turning on the electric pump brought the pressure back up. I replaced the mechanical pump and dissected the old pump. It appeared the diaphragm had a slight tear although no fuel or oil was leaking out of the vent tube. I thought the issue was resolved until it happened on climb out again, but it to the same extent. I started to surmise that it was a vapor issue. My fuel system is exactly to plans EXCEPT I added a 90 degree AN fitting where the fuel line exits the wing root. I decided that the 90 degree I added, plus the 90 degree at the tunnel, could be causing turbulence in the flow. To fix this I bent up two aluminum lines without any 90 fittings, the come together under the seat with an AN female coupling. That was two years ago and I have never seen the issue again. In addition, I am seeing a 1+ psi increase in the mechanical pump pressure.
Whether the pump was bad is in question

Another data point to consider, Ivan K had the exact issue you describe. He replaced the pump and it temporarily went away, but now still happens occasionally. I believe Ivan’s is plumbed per the plans. Geoff Combs has a continuous flexible line from his tank to his Andair fuel selector. He has never seen the problem.

I would not suggest over tightening the fittings. If they are not sealing with the proper torque, they need to be re-flared.

Open up the tunnel, and with a full tank of fuel, wrap every joint with a paper towel and let it set for a couple of days. A blue stain will reveal a leaking joint. Also look at the fuel pump vent tube and see if any fuel or oil is being vented overboard. This would be indicative of a leaking diaphragm

Hope this gives you a few ideas

[Kyle Boatright]

Originally Posted by togaflyer

Can a pump have a partial failure, i.e. pressure loss during a full power climb out.

Yes. The one on my RV-6 did. The symptoms were only evident in a climb with the electric pump off. I think the attitude of the aircraft was the determining factor - if the pump was fighting gravity, it lost pressure. Otherwise, it acted OK.

[Bill Boyd]

Kyle, I was just looking at your sig line. How close is that 2019 (?) RV-10 to being done now?

[Kyle Boatright]

Originally Posted by Bill Boyd

Kyle, I was just looking at your sig line. How close is that 2019 (?) RV-10 to being done now?

All of the flying surfaces and fairings are finished including paint, and I saw the painter last week and told him to expect the fuselage in a month or so. Once he paints that, it'll be final assembly time.

And in other calendar related news, today marks exactly 19 years since the first flight of my RV-6.

[jeffwhip]

Originally Posted by togaflyer

I took off this morning to escape a cold Georgia day for the Florida keys.
Start up check.
Warm up check.
Taxi to fuel, check.
Run up, check
Take off all normal and green. Boost pump off 1000 feet, fuel pressure normal.

Out of 5K for 9K, fuel throttle, 2700 RPM, I noticed the fuel pressure drops down to 12.8 PSI and starts floating between that and 13 PSI. Boost pump on, PSI back up to 25 PSI. Level off everything running normal. Shut boost pump off, fuel pressure drops to 18 psi and is varies one or two psi. Switched tanks with same results.

Pump back on, back to the hanger. Before shutting down I did a static run up to fuel power. With boost pump on 25 PSI, when switched off it drops down and varies around 18-20 psi.

Total time 180 hours. I think the pump is failing but its not old so checking to see if I should check other things before pulling it.

Please reach out to me if you need a new fuel pump. I took delivery of my Thunderbolt engine and removed the fuel pump because I'm using the EFII32 system. As such I have a Hartzell Engine Tech P/N 200F-5002 Fuel Pump I'd like to sell.

[togaflyer]

First, I wanna say thank you all for your input. It?s so nice that we have a great group of people on this forum who will take the time to help you out. The Cirrus group might sip Champaign with each other, but I would rather have a cold beer with this group any day of the week. I had to go out of town so the plane won?t get attention until I get back on the 15th. I plan to check out the system front to back when I get home. My fuel system is all Teflon lines with the only 90 degree turn at the tunnel from the tank. If the lines looks clean and tight, then it has to be a partial failure of the pump. When I have the problem solved I will report back on the results. One thing with the Garmin set up (and most new glass systems) you can look at the engine info for all the flights. Checking back on flight for months, the fuel pressure was the same 24-26 psi. This last flight was the sudden drop, down to 12.8 psi. I forgot to mention that before shutting down I did a full power engine static run. PSI with boost pump on 26 psi, with it off, 18-19 psi, compared to the normal 24 psi

[vic syracuse]

Originally Posted by Machsandy

Hello Vic

Please can you expand on ?make sure the fuel selector is tight?

If you have the original brass valve fuel selector, there is a nut on the shaft right underneath the handle. Use a wrench to take it off (after removing the handle). MAKE SURE YOUR TANKS AREN'T FULL.
Then the valve assy will comeout. You will see an O-ring on that shaft that dries out if it is not lubes once in a while (fuel lube works). Then the pump will suck air through the shaft.
Sometimes you will notice a fuel smell in the cockpit with full tanks, but not always. Air will leak where the fuel won't.

Vic