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Fuel Smell when FI electric pump on?

RudiGreyling

RudiGreyling

Well Known Member
Hi RVators,

My RV7 is about 1 year old and lately if I switch the standard Vans Supplied Fuel Injected electric pump on (during Take-off & Landing), I get a fuel smell in the cockpit.

I have confirmed with at least one other local builder he gets the same on 2 of his RV7As he build to exactly to plans, on the same standard setup.

I have taken the entire center floor pump cover section appart many times trying to trace this but to no avail.

My current modus oprandi is not to use the standby pump, to eleminate the fuel smell, but that is not ideal either.

Here are my questions:
1) Have you RV7/7A Fuel Injected drivers experienced the same?
2) How have you solved it?
3) What is the best method to trace a fuel smell? My approach of looking for gas seepage has failed.

Thank you in advance,
Kind Regards
Rudi
 
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Smell

I get a smell if I leave it on for a couple of minutes. If I remember to turn it off a minute or less after TO then generally no odor. I have always had this since day 1. I have noticed light blue stains on outside of fuel tubing under fuel selector valves during inspections but never fuel stains on the floor and I retightened all joints just to see if itwould help. I think it did just a little.
 
Fuel smell with electric fuel pump

RudiGreyling said:
Hi RVators,

My RV7 is about 1 year old and lately if I switch the standard Vans Supplied Fuel Injected electric pump on (during Take-off & Landing), I get a fuel smell in the cockpit.

I have confirmed with at least one other local builder he gets the same on 2 of his RV7As he build to exactly to plans, on the same standard setup.

I have taken the entire center floor pump cover section appart many times trying to trace this but to no avail.

My current modus oprandi is not to use the standby pump, to eleminate the fuel smell, but that is not ideal either.

Here are my questions:
1) Have you RV7/7A Fuel Injected drivers experienced the same?
2) How have you solved it?
3) What is the best method to trace a fuel smell? My approach of looking for gas seepage has failed.

Thank you in advance,
Kind Regards
Rudi
Click to expand...

Rudi,
I don't think this is RV-7 specific. There have been several threads about fuel smells, and most were throught to be normal venting issues. However, in a RV-6 fire (cant find the thread), the tubing to the fuel pressure gauge broke, and luckily the pilot got out on the ground, but airplane was destroyed. I had a similar smell coming in for landing when I hit the boost pump. After expediting the landing, I found blue streaks coming out the side of the cowling and down the landing gear fairings like my toy had wet its britches. The blue streaks traced back to the mechanical fuel pump where the copper tubing to the fuel pressure gauge snapped.
Hope you find the fuel smell source before you fly again.
Bill McLean
RV-4
http://www.vansairforce.com/community/showthread.php?t=12112&highlight=fuel+smell (maybe the link)
 
Fuel smell not "normal"

If I smelled fuel in the cockpit, I would not fly again until I had verified the source.

If you smell the vapor, there is potentially enough for ignition somewhere. One stray spark, and it might be another paragraph in the NTSB reports.

Why take a chance.? Fuel smell in the cockpit is not a normal occurrence. It is a health hazard and a potential fire hazard.

I do have one aircraft that has an occasional fuel smell in the cockpit. I know exactly where it is coming from and why. I did not fly it until I found the source and determined there was no possible fire hazard.

I have had a fuel pressure line rupture. I have also had the Vans fuel pressure sender spring a leak. The only clue was a slight fuel smell during taxi.

Just my two cents. YMMV
 
N131RV said:
If I smelled fuel in the cockpit, I would not fly again until I had verified the source.

If you smell the vapor, there is potentially enough for ignition somewhere. One stray spark, and it might be another paragraph in the NTSB reports.

Why take a chance.? Fuel smell in the cockpit is not a normal occurrence. It is a health hazard and a potential fire hazard.

I do have one aircraft that has an occasional fuel smell in the cockpit. I know exactly where it is coming from and why. I did not fly it until I found the source and determined there was no possible fire hazard.

I have had a fuel pressure line rupture. I have also had the Vans fuel pressure sender spring a leak. The only clue was a slight fuel smell during taxi.

Just my two cents. YMMV
Click to expand...

Thanks Joe,
I am aware of the dangers, but you are not realling helping, hence my questions here. Where was your occasional fuel smell without a danger?

To others,
I now have received 5 confirmed cases of RV7/7A with IO-360 and standard FI Boost pump that report fuel smells when the fuel pumps are run for different 'extended' periods. All these guys also report, that they could not find the problem either and live with it. They are also interested in any suggested fixes.

I'd really like to get to the bottom of this one, any suggestions?
Is there not a dye or spray on mix available that react with fuel to show any small fuel leakages?
Any other tips or tricks?

Kind Regards
Rudi
 
Are you using purge valve assembly? If I transfer fuel from the left tank to the right to cool the distribution block the fuel going into the right tank would force air from the tank causing a fuel smell. I find that If I leave the boost pump on for too long it will vent from the mech pump overflow. It only occurs when the engine is not running. It's not a large amount, a few drops can generate a lot of smell. Pull the lower cowl and see if your getting any bypass from the mech fuel pump or in the fuel servo into the FAB with the pump on.
 
RudiGreyling said:
Hi RVators,

My RV7 is about 1 year old and lately if I switch the standard Vans Supplied Fuel Injected electric pump on (during Take-off & Landing), I get a fuel smell in the cockpit.

I have confirmed with at least one other local builder he gets the same on 2 of his RV7As he build to exactly to plans, on the same standard setup.

I have taken the entire center floor pump cover section appart many times trying to trace this but to no avail.

My current modus oprandi is not to use the standby pump, to eleminate the fuel smell, but that is not ideal either.

Here are my questions:
1) Have you RV7/7A Fuel Injected drivers experienced the same?
2) How have you solved it?
3) What is the best method to trace a fuel smell? My approach of looking for gas seepage has failed.

Thank you in advance,
Kind Regards
Rudi
Click to expand...

Rudi,

I have 2 pumps similar to yours left over from a previous project that produce 28 psi when on. Neither pump causes a fuel smell when operating (at this time).

If either did, I would remove the entire package from the airplane, put it on my bench and double check every fitting for tightness, maybe even open each fitting and check the tube flare for nicks or imperfections. There is a tiny leak somewhere - probably at a fitting or it could be at the pressure regulator by-pass, it screws apart and may not be properly seated or just a little loose. If you are by-passing from the regulator back to a tank, it could be a fitting going in that direction. Something has changed that is causing the smell. There may be stress on one of the lines at a fitting.

I don't know of a process to find such a tiny leak other than make sure it is properly assembled. The flare process we use with soft aluminum tubing leaves a lot to be desired, it is less than precise. I have had leaks in the past and usually got them to stop by tightening the fitting more than it was. There also are available soft aluminum bushing to place over the fitting where it meets the aluminum tube, they work if nothing else does.

Good luck.
 
Make sure when you check your fittings for leaks that you rub your fingerstips around each fitting. Sometimes its hard to see the green stains on blue anodized fittings, but the stains will rub off on your fingers.
 
I have had an accessional fuel smell in my RV7A and it has been from day one but it usually appears when I am in a slow flying attitude (nose up with flaps down).

My buddy who has a RV7A has exactly the same gas smell issue and we have never been able to find the leak or why
I have double checked my fitting and found to trace of the blue stain or any kind of fuel with the pump on. Both have IO-360 with VAN's stock fuel pump.
 
Bavafa said:
I have had an accessional fuel smell in my RV7A and it has been from day one but it usually appears when I am in a slow flying attitude (nose up with flaps down).

My buddy who has a RV7A has exactly the same gas smell issue and we have never been able to find the leak or why
I have double checked my fitting and found to trace of the blue stain or any kind of fuel with the pump on. Both have IO-360 with VAN's stock fuel pump.
Click to expand...

Thanks Bavafa, that makes it now 7 x RV7/7A with such a problem. Maybe it is not the fuel pump, but in the take-off and landing attitude that just corresponds the same time the FI pump is on. I'd like to get to the bottom of this one...
 
Not exactly the same issue, but perhaps related. I had a bit of a fuel smell in my 9A that was intermittent (and only when on the L tank) and finally traced it to a slightly loose bulkhead fitting in the vent line. Normally there is no liquid fuel in the vent lines, but occasionally some would slosh into the vent line and if it sat there long enough, the tiny leak would allow me to smell it. Solved by tightening the fitting just a bit.

greg
 
Plain old talcum powder

works well in identifying fuel leaks. It turns bright blue. If nothing there then just vacuum it up.
 
I think you may be onto something

RudiGreyling said:
Maybe it is not the fuel pump, but in the take-off and landing attitude that just corresponds the same time the FI pump is on.
Click to expand...

Good catch on the not too obvious connection here......

Nose up attitude, ?? moving a bit slower???

Where are the fuel tank vents located??

Could fumes from the vents be getting into the cockpit??
 
RudiGreyling said:
Thanks Bavafa, that makes it now 7 x RV7/7A with such a problem. Maybe it is not the fuel pump, but in the take-off and landing attitude that just corresponds the same time the FI pump is on. I'd like to get to the bottom of this one...
Click to expand...

In the -8's, it is not uncommon to get a fuel smell in the pattern if the right tank is full. I have played around with it and talked to others, and believe it comes when a little fuel from a full tank burps out the right tank vent and gets picked up by the under-wing NACA scoop. Obviously, the configuration is much different on a -7, but the thought process is the same.

The only time I had a fuel smell in Louise's -6 was after we'd done some re-plumbing for a fuel flow sensor, and indeed, had a bad flare fitting. We found that REAL quick!
 
FOUND IT!

FOUND IT!

Ok after spending the whole of Saturday looking through the whole fuel system from wing tank roots all the way to the fuel distribution spider.

My leak ("more like a little sweat") was after the FI boost pump, at the Dynon Fuel Flow Sender outlet, sweating out the treads between the Feul flow sender and the Alu fitting.

It only sweats a tiny bit when the Boost pump is on, and the throttle is in fully closed position. During this configuration this line is under pressure, cause the boost pump is pushing, but the mechanical pump (low RPM closed throttle) on the other side and fuel requirement is very low. With the boost pump OFF this line is under sucktion hence no 'leak'.

I only found the 'leak' after everything was open and running the boost pump for several minutes, with the throttle and mixture closed on the ground. Even then it was only a slight wetness on your finger, when I run my dry finger around the fitting. It is AMAZING how easy one's nose pick up such a small amount of fuel in the cockpit. It was so little that any evidence of the 'leak' evaporated if you wanted to trace it after a flight.

Tightening the fitting did not help. I though the fuel flow sender was a tapered thread? Anycase I lossened the fitting and pipe flare at the fuel flow sender outlet, checked the condition of the fittings, flare and sender everything seamed in order. Then I put good amounts of fuel lube on everything and re-tighten it up.

I ground checked it again boost pump running, closed mix & throttle and then went for a test flight with boost pump running the whole short flight!

NOW it is sealed for good, and no more feul smell. Happy Days! :D

Now I am wondering if somehow i might have forgotten (doubt it) to put fuel lube on this fitting when it was assembled in the first place, and in the year's time down the road it decided it is going to 'leak' out the treads. That is my only explaination I can came up with.

I hope you other 6 guys find your fuel smell, it might be worth pressure checking it on the ground like I did, running your dry finger around every fitting in the system.

Regards
Rudi
 
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gasoline smell

Good job Rudi!

I agree with other posters that it is a really good idea to get the bottom of any gasoline smells - they usually indicate a leak.
 
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