If it ain't one thing it's another!

[DaV8or]

The day before yesterday I had to abort a flight and make a precautionary landing. The plane was running fine, but my engine monitor was indicating a fuel flow that was way too high. I was leaning in climb with the target method and was indicating 21.5 gph at altitude. I leveled off at 6500' and did the big pull. The best I could do to keep it from lean misfiring was about 9.5 gph WOT and 2400rpm. This is indicated to me that I might well have a fuel leak.

 

Returning to the hangar, I pulled the cowling and inspected. I ran the boost pump and couldn't find any leaks to the fuel servo. I visually inspected the hose from the fuel servo, the fuel servo itself, the flow divider, the injector lines and the injectors and couldn't notice anything amiss. I even put a wrench on the injectors because they had been changed at annual. They seemed plenty tight.

 

I them ran it up with the cowl off, shut down and quickly jumped out and inspected everything. Again I found nothing. So I buttoned it back up and decided to try flying it some more. Maybe it was an anomaly? Maybe the gauge is wrong?

 

I flew within glide distance of the airport and again, the engine ran fine, but indicated a high FF. Eventually it began to run what seemed to me a tiny bit rough, so I went back, landed and pulled the cowl again. This time, perhaps because I was more observant, or more likely because the engine ran longer, I could see the tell tale blue streaks of 100LL leaking. It seems 3 out 4 of my brand new GAMI injectors are leaking at the cylinder head.

 

Like I said, I had previously put a wrench on the ferrel nut that tightens the injector line to the injector and they seemed pretty tight. I did not put a wrench on the injector itself, the theory being that if the injector was loose in the head, it would turn when I turned the injector line nut and they didn't. I did not install these injectors, LASAR did.

 

Anybody ever have this problem? Is there supposed to be a gasket, or sealant used on the threads? Typing this post is actually the first thing I have done about this so far.   

[bonal]

Did they have the blue fuel dope on the threads. The reason I asked is when I had my annual done a few months ago I had a new OH carb put in. yesterday after completing my oil change we did a run up to check for leaks well they spotted a fuel leak on the fitting between the fuel line an the carb and it had the blue fuel dope on the threads. we pulled the fitting (and it was tight) and replaced with white pipe dope (not teflon). and the leak stopped.

[mike_elliott]

This is really a longshot, but did you also verify the K factor wasn't changed in the FF gauge accidentally or otherwise?

[Txbyker]

Dave,

 

Did it look like this?  I just went through the GAMI swap a month ago with leaks.  I used a stand-in A&P as my usual one was off that week.  The guy that installed them claimed he had done dozens but I had to have his work redone.  My usual A&P and I fixed it.  First, the leaking GAMIs were loose at the heads.  On mine there is not enough clearance to use a box end, open end or regular socket.  We had to take a 1/4" socket and grind the walls down thin, but not too thin that it would crack.  Each of my GAMIs turned at least another quarter turn.  I forgot the torque spec in inch lbs but it is snug.

 

Then the housing over the screen is supposed to spin.  The first A&P did not realize that and when you use the supplied GAMI washers they are thin and do not snug the screen housing tight.  You can misinterpret that as the screen housing is not supposed to be loose but all it does is cover the screen and allow air to seep in from the bottom to mix with the fuel.  There are some tiny holes in the GAMIs on the side under the screens.  So we removed the thick washers the first A&P had and put the GAMI washers back on and it allowed the feral to tighten good on the fuel line.

 

Also, a couple of the GAMIs that I was sent had rubber washers under the screens in the top and bottom position.  The bottom rubber washer is not supposed to be there on our non-turbo engines.  GAMI messed up sending me them that way.

 

Hope this helps as it fixed me up and I now have .1 GPH spread.

 

If your fuel flow is quite a bit higher than normal with no leaks it could be something else but just wanted to pass on my experience.

 

Russ

[rbridges]

that pic reminds me of a set of aftermarket headers I installed on a mustang.  the clearance was so tight, I had to borrow a buddy's wrench that he had ground on the outside to allow it to fit.  Sounds very similar to what you are describing.  I blew an exhaust gasket the first time b/c I didn't have his wrench and didn't tighten the bolts enough.

[N601RX]

There both a torque and angle spec on these. Going from memory I think it was 60 in lbs, but the hole in the side has to be up also. The hole is opposite of the marking.

[DaV8or]

This is really a longshot, but did you also verify the K factor wasn't changed in the FF gauge accidentally or otherwise?

 

That actually isn't that long of a shot really. The last time I filled the plane, strangely the estimated amount used vs. actual pumped was about 30% off!    I did push the auto correct button. I have no idea why it was 30% off and was shocked at the time. I have never put much stock in the "K factor" or the estimated fuel remaining. It never matches what I put in. I have never understood the K factor thing and assumed that when you install a fuel flow gauge that reads the actual fuel flowing through the pipe, not some adjusted, modified digital interpretation of what is flowing through the pipe. Perhaps I am wrong.

[DaV8or]

Dave,

 

Did it look like this?  I just went through the GAMI swap a month ago with leaks.  I used a stand-in A&P as my usual one was off that week.  The guy that installed them claimed he had done dozens but I had to have his work redone.  My usual A&P and I fixed it.  First, the leaking GAMIs were loose at the heads.  On mine there is not enough clearance to use a box end, open end or regular socket.  We had to take a 1/4" socket and grind the walls down thin, but not too thin that it would crack.  Each of my GAMIs turned at least another quarter turn.  I forgot the torque spec in inch lbs but it is snug.

 

Then the housing over the screen is supposed to spin.  The first A&P did not realize that and when you use the supplied GAMI washers they are thin and do not snug the screen housing tight.  You can misinterpret that as the screen housing is not supposed to be loose but all it does is cover the screen and allow air to seep in from the bottom to mix with the fuel.  There are some tiny holes in the GAMIs on the side under the screens.  So we removed the thick washers the first A&P had and put the GAMI washers back on and it allowed the feral to tighten good on the fuel line.

 

Also, a couple of the GAMIs that I was sent had rubber washers under the screens in the top and bottom position.  The bottom rubber washer is not supposed to be there on our non-turbo engines.  GAMI messed up sending me them that way.

 

Hope this helps as it fixed me up and I now have .1 GPH spread.

 

If your fuel flow is quite a bit higher than normal with no leaks it could be something else but just wanted to pass on my experience.

 

Russ

 

Mine don't look as bad as that, but kind of. Maybe 60% less blue.

[N601RX]

The flow sensor is just a wheel with pedals extending from it. As the pedals rotate by the pickup pulses are generated. The gauge measures the time between the pulses and then uses the K factor to calculate Gallons per hr.

[Guest]

There is a torque value for the fuel nozzle into the cylinder head, but I've never found a value for the line to the fuel nozzle.

Clarence

[DrBill]

My JPI450 is usually within 1/2 of a gallon at fillup.

[cliffy]

You need your K factor correct to show not only fuel used but fuel flow correctly. As was mentioned, a wheel spins and "cllicks"  as fuel moves past it into the engine. 

Let's say that 100 clicks of the wheel actually equals 1 gallon of flow. You tell your FF gauge that 100 clicks (the K factor) equals 1 gallon.  Then your fuel flow and your gallons used will be correct. If your K factor is set to say 110 "clicks" per gallon then more fuel will have to pass the wheel (10% more) for the gauge to show 1 gallon BUT you will have actually used 1.1 gallons so when you refill your tank you will need to add 10% more fuel than your FF gauge showed. Just the opposite if your K factor is set low, your gauge will show more used than you put in your tank. 

Check your manual and reset your K factor. It may take a few flights to get it accurate. In 30 gallons mine shows only .1 or .2 (tenths) of a gallon off actual burn.