will a cracked return line cause a lean condition?

[The motor guy]

I noticed the return fuel line on my blower was cracked cause the rubber was hard and brittle. I noticed the blower was running really really good the last couple days, with very little four stroking at all. It also idled a tad higher too, I don't see how that hose could suck air, but I guess it could. I figured the main fuel line would be the one to suck air.

 

[Dave9]

I'm not a small engine carb expert but from what I know that should make no difference because the return line just gives the primer bulb somewhere to move air (then gas) as it's a pump that pulls it into, then out of the carb through that return line. That is, unless your primer isn't sealing any longer, then I suppose it might be able to not only suck air in, but also before the line broke, could have been sucking fuel in through the return line so it was running richer than intended. Again I'm not an expert on small engine carbs, could easily be wrong.

 

[FowVay]

If the return line was damaged then it's likely that the supply line could also have a crack. A cracked supply line will allow air to enter the fuel feed circuit and this will reduce the amount of fuel going to the engine. This situation can create the lean condition that you mention. Air volume does not vary but fuel volume does and if the supply line isn't providing enough fuel (due to crack/air leakage) then the mixture ratio will be lean.

 

[izualangel]

If your return line is old enough to be cracked and brittle, then the supply side is likely in equally poor shape. Many manufacturers sell the lines as a kit to do them all at once.

 

[eljefino]

I've had 2-stroke weedeaters where the tank is pressurized (on purpose?) to force the fuel up. Any line problem would be a problem in that setup.