Fuel smell in cockpit

[nickmatic]

Been flying my new (to me) 252/Encore conversion for about 3 months now, so I'm still getting used to it in many ways.

 

But one thing that is alarming is that I smell fuel in the cockpit rather strongly on short final sometimes. It seems to happen the most and be the strongest when I close the throttle completely if I'm coming in too high, for example.

 

It may be the attitude (fuel moving forward in the tanks?) and not related to the throttle position, but I feel like I've noticed it more often when I've been too high (darn slippery airplane!) and cut the throttle abruptly.

 

This is rather concerning... any ideas what is going on?

[Seth]

Check to see if your rudder petal boots are torn, if so, then you will get air from the nose wheel compartment, and if the nose gear is down, you may get some exhaust gases, maybe the fuel smell is coming from there?

 

-Seth

[FBCK]

One of my tanks had a very small leak a couple of years ago and I experinced the very same thing.  The plane just stunk of fuel when sitting or moving slow but in cruise everything was fine.  Had Paul reseal both tanks in Wilmar and that went away.  Its a leak in one of your tanks more than likely.

[chrisk]

I'm under the impression there is a gasket around a fuel sender that may leak into the wing root.  Do you have blue staining anywhere?  Do you smell fuel when you get into the plane before flying?

[tomn]

Check you sending units from inside the cabin as well.  They can leak causing the fuel smell although you would normally smell that when you first get in before flying.  

[nickmatic]

I'm under the impression there is a gasket around a fuel sender that may leak into the wing root.  Do you have blue staining anywhere?  Do you smell fuel when you get into the plane before flying?

Sounds like it could be a lot of things. But I've absolutely never noticed a smell while the plane is sitting or in cruise. The only time I've ever smelled it has been on short final, and the smell comes on all of a sudden and last time it was quite strong. Not just "oh, is that fuel I smell?" But more like "Wow, that's gasoline. Hope I don't have to go around."

[moodychief]

Could it be fuel injectors? http://mooneyspace.com/topic/10383-leaking-fuel-injectors/

[aaronk25]

Could it be fuel injectors? http://mooneyspace.com/topic/10383-leaking-fuel-injectors/

Good idea but the only time I was getting fuel leaking from injectors was at WOT and high airspeeds, besides closing the throttle creates vaccine sucking the fuel in.

Oh and he has a turbo so there is not atmospheric vents as the injectors have upper deck pressure from turbo pumped into them.

I'm guessing gear down is creating some different airflow patterns and he has a leak somewhere else and that's the only time it's apparent......

Not sure

[mike_elliott]

If you are anywhere close to Willmar, take it to Paul Beck at Weep No More, LLC. He will sort it out. He can fix minor leaks in a few hours, and if it is more than that, you want to know anyway. Bottom line is, Paul will do you right. If it is a sender gasget, he will fix it and probably charge you enough to buy lunch.

[aaronk25]

Could it be fuel injectors? http://mooneyspace.com/topic/10383-leaking-fuel-injectors/

Good idea but the only time I was getting fuel leaking from injectors was at WOT and high airspeeds, besides closing the throttle creates vaccine sucking the fuel in.

Oh and he has a turbo so there is not atmospheric vents as the injectors have upper deck pressure from turbo pumped into them.

I'm guessing gear down is creating some different airflow patterns and he has a leak somewhere else and that's the only time it's apparent......

Not sure

[Marauder]

Do the Bravos have a low/hi boost pump capability? If so, what setting should it been on for landing? Curious to know if something like too much fuel is being provided from the boost pump.

[nickmatic]

If you are anywhere close to Willmar, take it to Paul Beck at Weep No More, LLC. He will sort it out. He can fix minor leaks in a few hours, and if it is more than that, you want to know anyway. Bottom line is, Paul will do you right. If it is a sender gasget, he will fix it and probably charge you enough to buy lunch.

Thanks for the tip. Paul sounds like the man for the job. MN is a bit far for me but I'll keep it in mind.

[nickmatic]

Do the Bravos have a low/hi boost pump capability? If so, what setting should it been on for landing? Curious to know if something like too much fuel is being provided from the boost pump.

Encore/252, actually. I have high and low boost pumps but I never use them.

[CoachTom]

Any chance your Gascolator might have a slow leak that puddles in the belly panel and until you are on final, your flaps change the pressure flows of the cockpit and the vapors come up?

 

This happened to me with a slow drip that i never noticed because i would always shut my fuel off after shut off, so no dripping until in flight.  During flight, the smells would be vented or drawn out of the aircraft until final and then the negative pressure of the cabin would suck the smells in with cowl flaps open...

 

I chased this down the long way from the wing roots on in to where i found the leak at the gascolator.  New gaskets on the gascolator and no more smell.

 

Hope you find it soon,

 

TMcD

1980 M20K

[nickmatic]

Any chance your Gascolator might have a slow leak that puddles in the belly panel and until you are on final, your flaps change the pressure flows of the cockpit and the vapors come up?

 

This happened to me with a slow drip that i never noticed because i would always shut my fuel off after shut off, so no dripping until in flight.  During flight, the smells would be vented or drawn out of the aircraft until final and then the negative pressure of the cabin would suck the smells in with cowl flaps open...

 

I chased this down the long way from the wing roots on in to where i found the leak at the gascolator.  New gaskets on the gascolator and no more smell.

 

Hope you find it soon,

 

TMcD

1980 M20K

Good tip, thanks. My mechanic is finally looking at it tomorrow morning and I'll chat with him about this and other possibilities that were raised here.

[captainglen]

Fuel smell means there is raw fuel somewhere this means a leak. The fuel could be leaking from the fuel system or the tank. To ruel out the fuel system components lines, pumps and carburator. To detect component leaks you can run the boost pump on the ground for 15-20 minutes and look for dripping from the belly or cowl. Another way to detect component leaks is to check for excessive fuel burn on longer flights although I would not reccoment flying an airplane with this kind of leak.

Remember that the inboard bulkhead of the integral fuel bays are part of the cabin walls behind the trim sidewall panels and this is where the fuel level sensors are mounted. Fuel leaking into other areas of the wing can cause the vapors to vent into the cabin. Fuel vapors in the cabin are a serious matter as are most leaks.

[BillC]

Nickmatic,

Please post your findings on the fuel smell.

Thanks,

Bill

[nickmatic]

Nickmatic,

Please post your findings on the fuel smell.

Thanks,

Bill

Oops, I thought I had. There is a leak high up in the right tank. As long as the fuel level is below the leak, there is no problem. But if I fill the tank to the top or when the airplane is pitched down on approach, a little fuel can leak out, flows down the wing dihedral, and through the cabin bulkhead, resulting in a smell.

 

I've spoken it over with a couple mechanics and they agree the work should be done by a Mooney tank specialist. For now I just don't fill that tank all the way unless really necessary.

[mcpilot]

Just curious  Does anyone have a photo of what the  leak at the wing roots look like?

[Zulee]

This topic is old but I've dealt with fuel smell twice and as many have posted, my problem was at the fuel send or pickup gasket...actually it was coming out around the screws.  I've attached a couple photo's so you can see what it looks like.  And by they way, I've had my tanks resealed by Paul within the past two years.

 

I tried to tighten the screws the first time around...and it worked...but only for a few months.  I am in my May annual and replacing both sides with new gaskets.

 

[Johnnybgoode]

x2 on post below, just in case someone runs across this issue and it's not a leaky tank. It was an RV-4 and only noticable with the boost pump on, mostly on short final. $20 or $25 for new gaskets/seals and it was fixed.

Patrick

Any chance your Gascolator might have a slow leak that puddles in the belly panel and until you are on final, your flaps change the pressure flows of the cockpit and the vapors come up?

This happened to me with a slow drip that i never noticed because i would always shut my fuel off after shut off, so no dripping until in flight. During flight, the smells would be vented or drawn out of the aircraft until final and then the negative pressure of the cabin would suck the smells in with cowl flaps open...

I chased this down the long way from the wing roots on in to where i found the leak at the gascolator. New gaskets on the gascolator and no more smell.

Hope you find it soon,

TMcD

1980 M20K

[flyboy0681]

I'm under the impression there is a gasket around a fuel sender that may leak into the wing root.  Do you have blue staining anywhere?  Do you smell fuel when you get into the plane before flying?

 

This was our problem. I noticed it for the first time when temps down here got down into the 40's, which is one of the tell-tale signs of the sender gasket needing to be replaced.

[Shadrach]

It could be the sending unit in the cabin, it coould be the outboard sending unit leaking and pooling in the wing and running down the spar. If there's a leak in the front of the tank, it will travel internally and pool at the fuselage outside the front wall of the tank. Check the underside of the wing to see if the vet holes are weeping. The scent can find its way into the cabin around the aileron control tubes.

Before patching my tanks, I cound induce cabin fuel smell with uncoordinated flight.