Fuel Smell When Leaning?

[Brian Scranton]

Fellers, just a quick question. Once I reach cruise, and after I set my MP and RPM, close my cowl flaps and begin my leaning procedure, I'll get a whiff of fuel. 

Any idea what's happening? It goes away after 30 seconds.

Thanks! 

[ArtVandelay]

Try just closing the cowl flaps, maybe nothing to do with leaning

[rbridges]

23 minutes ago, teejayevans said:

Try just closing the cowl flaps, maybe nothing to do with leaning

I was also wondering if leaning was coincidental with the timing.  

[Brian Scranton]

Will do--good idea. This is a pretty popular topic on Beechtalk, for what it's worth. Some problem areas have included the fuel sender, fuel servo, fuel return...and other guys have looked at all of those and still experience the issue. 

What's interesting is that it goes away after maybe 15 seconds never to return. And only on set up for cruise. 

[cliffy]

You might also check the condition of your "mouse boots"  (one in each main gear well)  for leaks, tears and missing altogether. Have found many boots damaged in inspections. They will let smells enter the cockpit from below.  

[Yetti]

Mechanical fuel pump leak, going bad,  Induction ball valve needs cleaning, selector valve leaking, Injector leaking, Injector line leaking, Do the mechanical pump up test,  http://www.donmaxwell.com/publications/MAPA_TEXT/External_Hoses/External_Hoses_Tubes.htm

Pull the cowl and look for blue stains

[carusoam]

Check everything for blue stains.

One thing that comes to mind is the fuel injectors have a vent hole.  Some vents leak leaving a bit of blue where it isn't appreciated.  I learned this from photos on MS.

If it is a regular occurrence, expect the blue stains to be easily seen.

Best regards,

-a-

[Brian Scranton]

Thanks guys! I'll dig in and look for blue! 

[slowflyin]

I've experienced the same thing but only during a GAMI lean test when I'm leaning very, very slowly.  Checked and rechecked, no blue.  Only the usual tad around the injectors.   Sent the entire system, servo to injectors  for overhaul and it didn't fix it.   I'd be interested to know your findings.  

[aaronk25]

I KNOW WHAT IT IS! you are running GAMI injectors right? They leak out the vent hole while leaning slowly and sometime continue to leak when fuel flow slows it just happens to coincide with right about peak and leaner.

The base of the injector is concave where lycoming a is flat across. I think the mooney induction system (and some beech products) is efficient enough where the pressure differential between intake and atmospheric is close and the concave gami catches a bit of the intake pressure spike when the intake valve snaps shut causing a bit of fuel to spit out the vent hole.

Back off .4MP and the problem goes away. Or get a refund on the GAMI injectors as even John Paul at GAMI couldn't make my plane run right with them.

Sent from my iPhone using Tapatalk

[jetdriven]

If you make a small air dam on #2 then the injector sits in calm air and it won't leak when running. The rest leak a little occasionally.  But #2 was a big problem it was leaking a lot of fuel out of the injector screen in flight. 

[aaronk25]

Byron,

On mine I couldn't get it to stop no matter what, even with the air dam. If fuel flow was kept up and ran ROP it was fine but as we all know that's not the point of having GAMIs. Mine is only about .3gph spread so I just stuck the lycs back in.

Sent from my iPhone using Tapatalk

[Brian Scranton]

1 hour ago, aaronk25 said:

I KNOW WHAT IT IS! you are running GAMI injectors right? They leak out the vent hole while leaning slowly and sometime continue to leak when fuel flow slows it just happens to coincide with right about peak and leaner.

The base of the injector is concave where lycoming a is flat across. I think the mooney induction system (and some beech products) is efficient enough where the pressure differential between intake and atmospheric is close and the concave gami catches a bit of the intake pressure spike when the intake valve snaps shut causing a bit of fuel to spit out the vent hole.

Back off .4MP and the problem goes away. Or get a refund on the GAMI injectors as even John Paul at GAMI couldn't make my plane run right with them.

Sent from my iPhone using Tapatalk

 

1 hour ago, jetdriven said:

If you make a small air dam on #2 then the injector sits in calm air and it won't leak when running. The rest leak a little occasionally.  But #2 was a big problem it was leaking a lot of fuel out of the injector screen in flight. 

 

1 hour ago, aaronk25 said:

Byron,

On mine I couldn't get it to stop no matter what, even with the air dam. If fuel flow was kept up and ran ROP it was fine but as we all know that's not the point of having GAMIs. Mine is only about .3gph spread so I just stuck the lycs back in.

Sent from my iPhone using Tapatalk

INTERESTING.  I am not running GAMIs but do have the turbo nozzles so they have the little hole opposite the A on the injector body. Totally possible that some fuel is squirting out there and #2 is always my hottest CHT by 15-20 degrees...however, there is no blue staining near or around the injectors. I flew today and leaned aggressively without closing the cowls. I DID NOT SMELL ANYTHING. BUT...there was some blue staining on the right nose gear door...too far aft to be the fuel servo, maybe it's the return line...I'll have to pull the cowl to see. So, I think I have eliminated the MP/Fuel Pressure gauge, the fuel selector, the spider, the injectors...

 

[Brian Scranton]

So, no blue stains anywhere (checked the nozzles and looked at/under the fuel servo), except on the gear door if I forget to turn the boost pump off after landing and taxi a ways with it on--but still get the fuel smell when I pull the mixture back. I have not pulled the panel under the pilot's seat to check the pump or the fuel sender. And the last time I replaced the MP/FP gauge, I tightened the heck out of those nuts (but I haven't re-checked in a few months--maybe I should). Doesn't happen all the time. But it's still happening. Hmmm...

[carusoam]

No drips on the hangar floor?

100LL may evaporate, but the marks it leaves may be noticeable...

check the drains of everything with a drain.  Fuel pump, electric fuel pump, sniffle valve (if the K has one), fuel selector valve...

 

Based on your description that it only happens while leaning...

What else happens while leaning?

On the ground ideas...

1) It might be interesting to see the leaning mechanism in action with the cowling off.  Does a drip fall out of anything while leaning?  It would be wise to get help from your mechanic and have a fire extinguisher nearby.  (Usual working with fuel ideas)

2) what happens when you pull the mixture out and you run the fuel pump?  (From the hot start technique for Continental engines.)   The IO550 returns fuel through a line to the selector valve.  Some engines run a line back to a tank.  

3) When the electric pump starts to leak, it drains out to the ground.  By the gallon....

 

Makes getting a small GoPro camera sound extra interesting...

 

PP ideas, not a mechanic..,

Best regards,

-a-

[Ragsf15e]

sorry to bump this, but mine does exactly the same thing when I lean.  I do have GAMIs and have make sure the "breather" holes are correctly positioned.  No blue stains... did you ever nail down the problem or a solution?

 

[75_M20F]

Mine does it too sometimes I have GAMIs as well. 

[Brian Scranton]

I did. I had a fuel hose resting up against an exhaust pipe burning a hole through it!!!!! That was one source for sure. 

Also, my fuel selector needed new seals. That was leaking a little so I saw some blue staining on the belly. 

And, at annual this year, removed my fuel servo and sent it out for a replacement--it was on its way out--sending flames out my exhaust on cold run up. 

And...I did find one injector with breather hole in the 5 o'clock position. 

 

[aaronk25]

The problem on my J was with the gami injectors. I removed them and reinstalled the factory injectors and no issues. The gami injector is concave on the bottom vs the flat lycoming injector. My theory is that there is some positive air pressure intermittently that travels back up the intake when the intake valve snaps shut. The concave design of the gami directs this up the injector and fuel spits out. The lycoming does not do this. Yes they were aligned correctly and every injector was changed at least 3 times by Gami. It’s a design flaw. Now what they should do is give us the turbo injectors with the inlets faced toward the high pressure air.


Sent from my iPhone using Tapatalk Pro

[Ragsf15e]

Thanks guys!  I’m gonna check it those injectors again.  It’s only while leaning.  I would think all those other issues would cause the fuel smell and leave stains all the time?

[aaronk25]

Thanks guys!  I’m gonna check it those injectors again.  It’s only while leaning.  I would think all those other issues would cause the fuel smell and leave stains all the time?

Exactly the problem I had. Let me guess just before peak egt and then crossing stochimetric mixture (peak egt) that’s when you smell it, I bet.

At ROP no problem, lean it out and fuel smell comes back. Alternatively reduce manifold pressure 1/2” the lean and I bet you a Ben Franklin there is no smell.


Sent from my iPhone using Tapatalk Pro

[ArtVandelay]

The problem on my J was with the gami injectors. I removed them and reinstalled the factory injectors and no issues. The gami injector is concave on the bottom vs the flat lycoming injector. My theory is that there is some positive air pressure intermittently that travels back up the intake when the intake valve snaps shut. The concave design of the gami directs this up the injector and fuel spits out. The lycoming does not do this. Yes they were aligned correctly and every injector was changed at least 3 times by Gami. It’s a design flaw. Now what they should do is give us the turbo injectors with the inlets faced toward the high pressure air.

I have Gamis and don’t have this problem. The fuel lines are routinely under 15-30psi, so where is the actual leak? At the injector,fuel line junction...maybe just a problem with the connection that was fixed when you installed new injectors?

[aaronk25]

I have Gamis and don’t have this problem. The fuel lines are routinely under 15-30psi, so where is the actual leak? At the injector,fuel line junction...maybe just a problem with the connection that was fixed when you installed new injectors?

Glad you don’t have this problem. It’s a pain. 15-30psi is the similar to house water pressure. Unless the line is finger loose that ain’t the problem.

I bet I have 50 hours into diagnosing this issue. On you tube there was a banana driver who actually put a camera on the gami in flight to show the fuel spitting out when leaning.

Gami should have stepped up.


Sent from my iPhone using Tapatalk Pro

[75_M20F]

I have GAMIs and if I close the throttle slightly before leaning I don't get the fuel smell. Either way it goes away shortly after I notice the smell.

Directions say to not tighten the GAMIs more then 60 inch pounds, but at 60 inch pounds they are facing the wrong way. The letter is not facing down..... What are you guys doing about that?

Do you use any kind of lock tight or anything on them when installing?

 

 

 

[Browncbr1]

5 hours ago, ABCDEF said:

I have GAMIs and if I close the throttle slightly before leaning I don't get the fuel smell. Either way it goes away shortly after I notice the smell.

Directions say to not tighten the GAMIs more then 60 inch pounds, but at 60 inch pounds they are facing the wrong way. The letter is not facing down..... What are you guys doing about that?

Do you use any kind of lock tight or anything on them when installing?

 

 

 

Maybe try some different thickness washers until you get the correct torque at the correct position?