K2500 burb evap leak

[MX-RV]

Hi there. We have just acquired a new to us 2010 k2500 6L 6l90 3.7 burb. However with the gas cap tight and in good condition I keep getting a p0442 evap leak at ~750miles after erasing the code it returns. The vehicle also smells of gas when filled full which leads me to believe it's the sending unit. Has anyone experienced this if so how easy is it to replace without a lift. I heard this truck may have two linked tanks although I have been unable to see under it well enough at this point to tell. Has anyone done this job does it suck badly or is it like most under vehicle jobs hot cramped awkward. Are the break lines at risk of corrosion above the tank like the old s10 and blazer were?

Thanks for any incite you may have.
MX

[MX-RV]

Thanks burbman you said it took a month of evenings was the vehicle usable during the day mostly? Do you have an idea of costs? I'm especially interested in doing the break lines but currently I have trip plates on the truck until I sell the old one and need to have a "drive clean" done to finish licensing it before the 15th. I'm thinking I'm going to have to bite the bullet and get the tanks fixed and do the lines later.

[BurbMan]

Yes, you have 2 fuel tanks unless they changed something in 2010. The rear one is up above the spare tire carrier, the main one along the inside of the driver's side frame rail under the driver's seat and rear seat. Bad news is that the evap cannister is located above the main fuel tank. Each tank has its own in-tank level sensor and electric fuel pump. The fuel filler feeds the rear tank which is connected to the front tank by a filler hose. The rear pump cycles on/off and sends fuel to the front tank according to instructions from the PCM.

There are evap lines that connect the rear tank, front tank, cannister and engine.

You can drop the tanks at home. Last Spring I removed both tanks and replaced both fuel pumps, all of the fuel lines and brakes lines with stainless. Yes, GM still uses uncoated steel for the lines and they corrode above the fuel tank. Whole job took me about a month of evenings and weekends.

[MX-RV]

absolutely it has definitely affected the mileage. does any one know if the transferflow gm 2500hd oem replacement fuel tank will fit. not sure as some say its a dual tank..

thanks

[carringb]

If the leak is bad enough you are smelling fuel, you are also losing MPGs because you are losing vacuum through that leak.

Often there is a soft elbow at the evap canister, and this is a common source of a large leak. But really, any of the vacuum fittings can fail, and sometimes rodents decide it makes a tasty snack.

The cheap way to pinpoint is to use a vacuum pump with gauge, and isolate each branch of the evap system. This can be time consuming however. Shops usually use a smoke machine to find the leak quickly.

Also, check the fuel filler hoses, including the crossover hose. Those can crack, and besides being an evap leak, could slosh fuel out.