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High Fuel Flow 11.5gph

J

jimcorley

I'm New Here
During the last week the following incident occurred to my RV12 4 times, Twice after takeoff 2 and twice while using climb power above 2500 feet.

In all cases suddenly the fuel flow reading and the red high fuel flow warning light would come on on the Dynon 180. An aural warning also would say "HIGH FUEL RATE. The fuel flow had jumped to 11.0-12.0 GPH. This would continue for about 5 to 10 seconds, at which time the fuel floe would drop to around 8 gpm. The engine always ran smooth every time and all engine gages ran normal.

Has anyone heard of something like this before?. The flights all continued as we were just doing local work. No evidence of anything wrong was found after landing. On 1 instance my passenger said He smelled fuel.

There is possibly some fuel residue on the runoff plates under the carbs.
 
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jimcorley said:
No evidence of anything wrong was found after landing. On 1 instance my passenger said He smelled fuel.

There is possibly some fuel residue on the runoff plates under the carbs.
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I'd check the float in both carbs and see if they are still floating. Bing had some problems with them before where they turned into divers and let the fuel flow freely which would then spill over. As the fuel pump is always on, the rate of spill over would be quite high.
 
Pretty much impossible for a 100 hp engine to use 12 GPH so either the fuel is flowing out of the carbs externally or the flow transducer is gibbled and giving false info. Once the AFR gets to about 11 to 1 you'll get rich misfire and the engine will lay down and run rough.
 
Possible Fuel Leak !!!!!!

I had a similar experience. My fuel flow jumped to 7 - 8 gallons per hour. The high fuel burn rate was caused by a leak in the engine driven fuel pump. Oddly enough I didn't smell fuel until I started descending. I would suggest that you don't fly anymore until you check out that possibility. I removed the upper cowl and turned on the electric pump and found fuel dripping out of the vent hole. Turning the propellar would also cause fuel to leak from the pump.

Don't doubt your flow meter its probably telling you something.


Gary
 
There have been issues with fuel pump leakage before and you have those carb drip trays of course. Amazing what sort of fixes the factory comes up with for carbs... Sounds like stuff you'd find on the Wright Flyer. I know you can't take the approved carbs off but EFI solves both of these issues plus several more.
 
Fuel leaks are dangerous

It does not take much gasoline in a confined space to explode. Read about the RV-10 that exploded and was destroyed:
http://www.vansairforce.com/community/showthread.php?t=57715 There is a picture of the plane on page 3.
Years ago my son and I built a potato gun. After much experimenting with various fuels and quantities, we found that exactly 1cc of gasoline measured with a syringe gave the best results. It does not take much to explode.
Joe
 
"No evidence of anything wrong was found after landing. ."

Jim, was your actual fuel consumption higher than expected...or was the high fuel flow rate *indicated* to be high? Fueling on your return would tell you which if you ran at an indicated 8 gph, as you stated.

"On 1 instance my passenger said He smelled fuel"
Just as a very small amount of fuel can be extremely explosive, so can a very small amount of fuel create a noticeable smell. There may be an actual leak even tho' the fuel consumed in flight seems to be normal.

Jack
 
No Evidence Found

I didn't find any evidence of a fuel leak until I ran the electric boost pump. No staining etc. was found. When the fuel pump was energized, fuel leaked out of the pump vent hole at a high rate, approximately a drop a second. Don't fly until you verified the integrity of the pump! Trust your instruments, a sudden jump in fuel consumption means something. Trust me, I've been there.

Gary
 
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Jim,

FWIT Don Rivera at AFP has a fuel injection system for the Rotax 912.

Carburetors are a little dated no matter how you cut it.
 
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fuel pump leak remedy?

I've had the same issue. The fuel flow meter has been consistently showing 7-8GPH fuel burn, but my actual usage is ~3.5 GPH. On a long cruise climb the reading bounces over the threshold of 10 GPH and sets off the alarm. Since I've had other sensor problems, I was suspicious of the fuel flow sensor reading. You guys that have had mechanical fuel pump leaks, did you remove and replace?
 
increase the K-factor

The fuel flow meter has been consistently showing 7-8GPH fuel burn, but my actual usage is ~3.5 GPH.
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The K-value needs to be changed as described on page 6-14 of the FlightDEK-D180 Installation Guide. The general rule of thumb: if your GALS (or LTRS) USED reads higher than you expect, increase the K-factor.
Joe
 
Thanks Joe, my plan was to adjust the K-Factor in the Dynon software. It's at 68000, the standard for the fuel flow sensor that is installed. I'll need to adjust up quite a bit to go from 8 down to 3.5? After reading the posts in response to the original question, I want to rule out fuel pump leakage first.
 
K Value

Adjusted K factor . Fuel flow rates have gone down and Usage has also decreased. Still must do some follow on checks to insure that was the real problem. Will be testing over the next week or so to get some good comparisons.Want to insure there is no leakage!

Thanks for all replies. Willl advise of results in the next week or so.
Jim



Mich48041 said:
The K-value needs to be changed as described on page 6-14 of the FlightDEK-D180 Installation Guide. The general rule of thumb: if your GALS (or LTRS) USED reads higher than you expect, increase the K-factor.
Joe
Click to expand...
 
Hello GDS

Yes I replaced the pump with a new one under warranty. Still waiting for my refund from Lockwood. The fuel flow meter now indicates between 4.5 and 5.5 gal / hr now depending on MAP. Everything works good now.

Again, I suspected my carbs first since I couldn't find any signs of leaks etc. Turned the electric pump on and found the leak on the mechanical pump. Caught an a whif of fuel once while climbing out and descending.

Gary
 
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