914 over fueling

[rhtrudder]

Finally finished changing all the fuel lines and filters, went flying, engine started to run rough below 4500 , managed to get back on the ground where it stopped with fuel dripping from the exhaust, towed it back to the hanger , discovered the right side carby running fuel with the pumps on , pulled it apart can’t see anything fitted it back on, seemed ok , got it started , try again but noticed the fuel pressure above .6bar map gauge 40 on take off, unsure whether the fuel pressure is running to high and forcing fuel past the needle, so I put it back down again , wondering whether something ended up in the fuel system from the new lines and was keeping the seat open , 

[skippydiesel]

No experience with the 914 but would expect system to work same/similar to 912 when it comes to fuel delivery:

 

I would not expect such a low fuel delivery pressure to be the problem.

 

When you say "right side carby running fuel" - where from ie down outside float chamber/bowl ? , out of carby throat ?

 

If running down outside of float chamber - could be the sealing  gasket has been dislodged/pinched/broken when you installed it.

 

• Inspect flat bowl gasket - replace if damaged, otherwise just re install making sure it it correctly positioned (I use a dab or two of grease to hold in correct position)

 

Floats and or fuel cut off/float valve may be a malfunctioning.  

 

• Check floats for correct buoyancy, weight, free movement.

• Check float fuel cut off valve working as expected, free movement, effective seating/sealing.

 

 

In an effort to remove /minimise risk of  manufacturing /storage dross entering fuel system I use a blast of compressed air to clear new lines befor fitting.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[rhtrudder]

Leaking internally, talked to wal, he seemed to think it was something caught under the needle or sinking floats, about to go flying always a worry when engine can get go you airborne and then starts to play up , not a lot of room to get back to my strip

[skippydiesel]

48 minutes ago, rhtrudder said:

Leaking internally, talked to wal, he seemed to think it was something caught under the needle or sinking floats, about to go flying always a worry when engine can get go you airborne and then starts to play up , not a lot of room to get back to my strip

Before further flight - Suggest extended run up, including full power, high speed ground run - then recheck for leaking, assuming no other symptoms.

Edited January 31, 2021 by skippydiesel

[rhtrudder]

Yep , did that, seemed ok, blasted off, all good, figured it must have been a stuck needle. 

[skippydiesel]

All good but It might be worth:

 

• Take the fuel feeds, of each bowl in turn, turn on auxiliary fuel pump & "flush" the system for a minute or two (repeat for each carby).
• Remove each float bowl , inspect for contamination and clean
• Similar for the  mechanical/main fuel pump fuel supply but use tank pressure/gravity to flush lines (or gently pressurise supply tank)
• Check filters for contamination.

[rhtrudder]

Thanks skip