I decided to start routing the CNG line at the fill nozzle, mounted on the rear frame. I used 316 Stainless Steel line, it will not rust or corrode. Unfortunately it is extremely hard and difficult to bend. It required a variety of forms to accomplish a smooth bend line. I also used a piece of 1/4" copper water line to make a template form. This worked out well as it limited the number of times I had to crawl under the Trailblazer and back out.

Here is all the bags of 316 Stainless Steel fittings I used to do the plumbing. All the line fittings are #4 JIC 37 ° flare. I used O-ring Boss fittings on the HPL (lower right) and 1/4" pipe thread adapters for the check valve.

Here is the first leg of the CNG line. It runs from the fill nozzle to the check valve. I added a fancy rubber isolation damper around the line to keep it from rubbing on the body. There is another damper where the line rounds the top of the frame cross member.

This is a a pic showing the plumbing of the check valve and inlet line to the CNG tanks. I used a bulkhead fitting to pass from under floor to above floor. The tee allows the CNG line to route to the engine compartment.

This is a close up of the check valve. I had to use an adapter on both sides of the check valve to plumb it into the main line. I had a check valve from a Cavalier, however it's connections were O-ring Face Seal and to adapt that would have been ugly.

Here is another pic showing the main CNG line running along the frame rail.

I used Stainless Steel Rubber-Cushioned loop clamps to hold the CNG line in place. I got them at a reasonable price from Jegs Performance Auto Parts. 2 packs is all you will need.

A better view of the clamp. I also used Stainless Steel self taping screws to hold the clamps to the frame rail. I needed to pre drill the hole as the drill end of the screws were not long enough to pass through the frame.

Every place the CNG line touched the frame I wrapped it in a 4" length of high pressure fuel line and zip tied it in place. The fuel line is extremely tough and makes a great insulator.

Here is the last pic before the front frame standoff. From here it is up to the engine compartment.

Another shot looking up a bit into the engine compartment.

Here is a view showing an empty clamp that use to hold the ABS cable. I had to reroute it to clear the CNG line.

As you can see I finally made it to the engine compartment.

It is too bad that 304 stainless will rust slightly. The 316 stainless tube added a bit if difficultly to the task. Especially at the engine compartment where some precision bends needed to be made. I am glad this task is nearly over.