C-15 Questions???

There should already be a checkvalve in the fuel system. I'm not sure if the 6nz uses the same filter head as the ACERT but on the ACERT it's just to the right of the filter right beside the filter, screws in from the bottom and takes about a 1" wrench IIRC.

 

There is a check valve in the transfer pump and a check valve in the secondary fuel filter housing on the engine. It should be on the return side, you will see a arrow pointing out and on the bottom should be the return check valve. You might had some gunk there

 

sounds like an alge infestation or your rubber lines are starting to fall apart from the inside.

 

Sounds like the tanks are dirty inside or you may of got a bad batch of fuel that was dirty. AS far as the not cranking good after setting a few days that is probably the injector o rings letting fuel leak back down into the cylinders possibly just one or a few.. If it is huffing alot of white or grey smoke when if first starts up that is exess fuel that has leaked down in the cylinders and is combusting till it cleans its self out it usually takes a day or two setting to leak that much down so if thats the case it needs the injectors pulled and all three orings replaced on each of the six injectors.

sometimes they are hard to pin point which one it is. those cats will do that somtimes depending on how many miles they got on them. The o-rings finnally just get old and brittle. Good luck with the problem.

 

do you have an actual spin-on filter or one of the old style canister type on the frame? the canister type can be cleaned, spin on just replace. if you see any kind of slime in the canister or screen then it is alge or bad fuel.