Fuel Smell with mixture change?

[Randy]

Regarding IO-375 with Silverhawk Fuel injection, on RV7A, now with a little over 100 hrs since new.

I finally have to ask this question. I have been chasing after the cause of a fuel smell I get in the cockpit in flight. After checking all fittings over and over and flying more I have come to realize that I get the smell when I change mixture settings, especially when going from ROP to a LOP setting. At lest that is when I notice it most consistently.

It did seem more prevalent when I had really filled my tanks and flooded the vent lines, (I did not find a leak) but I still get the smell even with partially filled tanks, when I pull the mixture towards lean. In steady flight when I don't mess with the mixture I do not get the fuel smell.

I have fuel stains around all four of my inectors on my IO-375 engine.

I have read that it is not unusual to have the stains around the injectors. I have tightened the top fitting on them ever so slightly as they look so fragile but the stains persist.

Is there any logic to this?

Is there a reason for the injectors to vent some fuel out when pulling the mixture towards lean?

My next course of action planned is to pull the injectors and clean them. This engine sat for a year or so after being run so perhaps there could be some build up os some kind to clean out, however my Gami spread is around .3 GPH, they seem to be fairly well matched and I can run around 100F LOP with a smooth running engine. I find no stains or leaks around the servo.

I really don't want to try to explain to passengers about a fuel smell. I sure don't like the images that come to mind when I smell fuel in flight and I don't imagine my passengers will either...

This is one of those things I have learned the hard way. There is always a reason for strange smells and sounds from our engines and it is wise to find and cure the cause if possible.

Any ideas?

Randall in Sedona

[RVG8tor]

Get an explosive gas detector. I had a faint fuel smell for along time and never could run it down. This detector is so sensitive I eventually determined one of my fuel tanks had a rivet on the back side with a very tiny leak.

The vapor would migrate to the center section of the wing spar and this is what gave me the fuel smell the every time I opened up the plan after it had sat over night.

They run $200 or so but I use it every annual now to sniff all my fuel connections. If there is a leak you will know it, they are very sensitive.

Cheers

[JohnInReno]

I had blue stains around some of the injectors but not all.

For some reason, the mark, "A?", showing how to orient the injectors is on the bottom where you can't see it. I marked mine on the hex flat 180 degrees away with a punch to identify the cylinder number and make orientation easier.