In search of a one way check valve I could use in my lift pump setup instead of a ball valve. Needs to support 1/2" fuel line and be as short as possible. I found Aeromotive and Earls on Summit's site but they are AN fittings ...and I'm not sure if I can adapt AN to 3/8" NPT hose barb and what size AN I would need to get? I assume the stock fuel system could pull fuel thru a check valve or would that depend on the design of the check valve?

Swagelok and Parker both offer check valves you could probably use. They have a wide variety of inline ck valves which could suite your needs. They offer them with npt ends also. They are probably pretty pricey. We use them in power plants quite often.

As far as AN sizes. They are equivilent to the number of 16th's. Therefore a -8 AN is equal to 8/16th's or 1/2". 3/8" is a -6.

Good luck with your fuel system.

Perhaps a PCV valve? They are fuel proof, light resistance, and can be found in large dias and short lengths. And cheap!

Based on my research the Parker's are only offered with a minimum cracking pressure of 5 psi. I found the Swagelock web site and think I found one that would work. They go down to 1/3 psi cracking pressure. I assume this is the pressure needed to pass fuel? Would 1/3 psi work? I would be using it in the diagram below in place of the ball valve. I'm not going to use the FM100 ...so that would be my Racor filter. the plan is to use the carter via cab switch or hobbs switch (on demand) where fuel would normally flow via the check valve.

Here's the link to the check valve I'm considering.
http://www.swagelok.com/PRODUCTDETAILS.asp?PartNumber=B%2D8C4%2D1%2F3&Price=&Picture=SS%2D4C4%2D1%2Ejpg%26CTSCKey%3D18

http://home.comcast.net/~tophog/duramax/images/Liftpump.jpg

Why do you need anything in the system at that point? Later! Frank

When I turn on the Carter it will want to pump fuel back up the bypass since the bypass circuit is not pressurized? I can tell the pump makes a completely different noise when the bypass is open ...like it's just sitting there cavitating ...and when I close the bypass it sounds like it's actually pumping.

Why do you need anything in the system at that point? Later! Frank

I'm actually proceeding down the path of McRat's suggestion :) of using a PCV valve ...just need to find one with both 1/2" in/out ports. A PCV valve should work fine ...bought one today even though it has 1/2 inlet and 1/4" outlet just to check it out ...and I think it will work perfectly for what I'm looking to do.

Without the check valve the Carter just pumps fuel in a circle. Your pressure and flow will be purely from the FM100.

And considering I'm not going to run the FM100 I wouldn't have any pressure :eek: Picture my existing secondary Racor in the diagram where the FM100 is.

Mcmaster Carr sells alot of that stuff.

http://www.mcmaster.com/

Thanks for the help everyone. I did find a decent 1/2" check-valve which I plumbed in last night and seems to work great. The downside is I ended up with less then what I origially planned where I would have a continous pump and the Carter for on-demand use.

I have one last question before I sell or send the FM100 back. In all my haste to get a LP setup I ordered an FM100 setup. My original intention was to use this as my continuous LP and the Carter as on-demand via switch until I learned the FM100 is only rated at 40gph.

I still would like to use the FM100 and my "existing" plumbing with minor modification if possible. I understand I would need to run the FM100 and Carter in parallel in order for the Carter to get sufficient fuel on the input side.

Since I cannot feed the Carter from the FM100, could I use the FM100 as I have it in the diagram and use a 'T' on the input side...where I could run a hose to the Carter bypassing the FM100...and then run the FMm100 output hose to the 'T' after the Carter where both hoses would meet? It seems to me this would be placing the 2 pumps in parallel and would also allow the Carter to eat as much fuel as it wanted, albeit unfiltered but I'm only going to run it via switch in cab and probably not very often ...it should last a while I would hope.

The key is if there are any issues with using a T on the input side of the FM100 ...

Any input would be appreciated.