R

Redbud

Member
Sponsor
I posted this on the 9A forum too. I’m looking for any help I can get. It’s an O-360 in a 9A. The problem is fuel pressure when the plane is hot. Following is a video demonstrating what happens. Could this be Vapor lock? Or something else? Thanks for taking a look!

https://youtu.be/u27zswGk_D8
 
Kevin, I listened and watched the vid, but still not sure what symptom you are seeing. Could you articulate the problem/concern please? Does this manifest in any operational way? i.e. under power
 
The engine loses power and quits when run up. I purchased the plane and attempted takeoff in Jacksonville,tx. The engine quit as the nose wheel lifted. This was after 2 previous successful takeoffs. The plane was delivered, after an a&p checked it out, to KSAR. The ferry pilot needed a ride to west Memphis. The pilot who took him ( I need transition training) got stranded there when the engine quit again upon runup. This was after 2 successful flights. Pump problems? Obstruction of something? Vapor lock? It was hot. I have to get help to West Memphis to fix and retrieve the plane. Thoughts from anyone who has had something similar happen would be appreciated. It’s an O-360
 
Does the problem happen with either one of the fuel tanks in use?
You may want to check that the fuel vent lines aren't blocked, which might require a disconnection at the tank end and blowing in the tube.
 
That’s a good question. I’m embarrassed to say I don’t know. I’ll ask the pilot who attempted to leave west Memphis and who made the video.
 
Vapour lock ?

The engine is hot after landing. When more than 2-3 min have passed the fuel
line will be hot. It is normal to see vapour lock when engine is hot.
After engine start, run the engine at 1500 rpm for a few minutes to get cooler
fuel in the lines. Then taxi to run up area. The engine should run without faltering at full power and at 700 rpm. Then it's ready for take of.

Good luck
 
Fuel pressure/vapor lock

Looking at your video, one thing is clear, you have little or no fuel pressure??
Assuming the indicator is correct you are showing 0.1PSI without boost pump and 0.6 or there abouts with the boost pump on.
There is a high probability that you are dealing with a vapor lock situation.
Vapor in your fuel pump will simply cavitate the pump as it cannot pump vapor.

I see that you need to get the plane home and one way to start the process of elimination would be to try an early morning run up and see if the low fuel pressure and engine quitting on run up persists. If it runs as it should, one could be fairly certain that you had a vapor lock issue.
If that fuel pressure does not come up (4 to 5) psi with a cold engine compartment you have several other options to consider, none of which involves flying home before getting it fixed.
Let us know what you find and please be safe.
 
Thank you to the 2 previous posters. Both offer good advice. It ran fine cold with good fuel pressure.
 
I had this problem when ferrying my airplane after I bought it (RV9A/IO-320). Started and ran fine at its home airport. My CFI and I were trying to fly it from St. Louis to central Minnesota. We stopped for fuel at Mason City, Iowa (where the music died) and trying to take off after lunch and refueling, we had almost the exact same symptoms that you describe. Long story short, we replaced the engine-driven fuel pump and all was well. We did have to fly it 20 miles on the electric pump to Forest City where the mechanic was.

This may not be germane to your problem since I have fuel injection, but these days...when it's hot out, the engine is hot, and a long taxi, I get variable fuel pressure and the the engine runs rough. But all those issues, including the fuel pressure variability, go away when I push the throttle in for takeoff and when I'm flying. I did wrap the fuel lines and added some exhaust shielding and that improved my situation.
 
It ran fine cold with good fuel pressure.
Click to expand...

That's good news!
Vapor lock happens even in certified aircraft and with avgas.
The fact is that every RV firewall forward is built just a little different.
The issues affecting what appears to have been vapor lock can be addressed when you get home.
As a mogas user and I am not turning this thread into a mogas vs avgas debate, I know a thing or two about how to avoid vapor lock issues.
The fuel pump or as I call it the "fuel boiler" is the worst of the offending components of anyone's fuel system. It is attached to a hot engine block that easily transfers heat to the fuel pump body and causes fuel to boil exactly where liquid fuel is most important. This condition is especially prevalent after a hot restart and prolonged taxi. Your engine may idle "ok" but as soon as you need power and flow the pump will cavitate and the engine spudders or dies all together.
Without addressing the entire fuel installation I can highly recommend that your fuel system be set up for minimal exposure to heat. By that I mean fuel lines are to be kept as far away from exhaust stacks, minimize length and hose installation FWF to a bare minimum. A fuel pump shroud and a cooling blast tube is a step in the right direction to keep the "fuel boiler" temp down a bit.
There are other more effective installation options for preventing vapor lock but may not be necessary if all you plan to use is avgas.
 
The plan is to travel to West Memphis this week. Very early in the morning! I’m taking not one, but 2 a&p’s that I have trusted for years working on my airplanes. If it fires up and runs with good pressure, then home we go. And then figure out the problem and fix it! Once again, thanks for the advice. I’ll post here what we do to diagnose and fix.
 
Back to KSAR

On Monday, I traveled to KAWM to retrieve the plane. With me we’re 2 a&p’s. One is also a CFI who has the check off, per the insurance company, to fly it back to KSAR. A heat shield was fabricated prior to the trip for the exhaust close to the gascolater. That was installed along with fire shield on fuel lines that were unshielded. We still had an issue with fuel pressure. Fuel pressure showed 0.1 to 0.3 pounds of pressure. Removing the fuel line and running the boost pump proved there was adequate pressure. And fuel flow looked normal. We still heard some cavitation from the pump. We decided to go. After taking off, we climbed to 7,500 and had no issues during the flight to KSAR. Since then, the fuel system has been examined from the tanks to the carburetor. The system could have been sucking air from 2 places. A leak was found on one of the lines on the fuel selector. There were blue stains on the floor below the selector. Another source of air was a return line that wasn’t properly sealed. After work was completed, pressure showed 0.6. It was actually 6 pounds of pressure due to the way the system was programmed. I think the problem is fixed.
 
Pics

IMG_3374.jpg

IMG_3371.jpg

IMG_3372.jpg

Pics showing fuel stain by selector, heat shroud and fire shield
 
I agree. It’s due for inspection in September. We’ll address it then. The shop had other stuff booked and did me a favor by slipping me in. They also installed the anti splat mod on the nose wheel and the convenience bar under the seats. I’m waiting on a new asi from vans as the plane had an incorrect one. And it wasn’t working properly. Also oil change. We’re doing the almost an rv14 seat mod too.
 
Redbud said:
I agree. It’s due for inspection in September. We’ll address it then. ...
Click to expand...

Might want to take a look at the RV-14 FWF plans for ideas about how to route your fuel lines better. There have been off-field landings when the fuel line fittings came loose, due to the non-standard design.
 
Will do. Thanks! I’ve owned certificated airplanes. That’s the way I’m treating this one when it comes to any maintenance. Avionics not included!
 
You must log in or register to reply here.