So you read our blog post about CP3 Conversions and the differences in them all, and you picked up one of the kits recommended. In this post, we will be discussing fuel line routing of the John C Garage Low Pressure Fuel Line kit, as well as the JCG Return Line Fitting Kit, which is an add-on to these kits.
The fuel line routing of the John C Garage Low Pressure Line kit is fairly simple, but for many DIY'ers, the first time it can be a little confusing. The low pressure line in question is the fuel line feed from the tank/lift pump* (if applicable). This low pressure fuel is either pulled under a vacuum by the injection pump, or supplied via a lift pump at 8-12psi towards the engine.
From factory, the low pressure line is a metal hard line that comes from over the
drivers valve cover and runs in the valley under the Y-Bridge to a large compression fitting. This is what the JCG Low Pressure Line set out to replace, as it was noted most times, the connection was not properly reinstalled, resulting in a valley full of fuel and eventually running down the back of the block over time due to a leaking fitting. The JCG Low Pressure Line runs a quality rubber fuel line outside of the valley and makes it easily accessible.
Above is an example of a 2012-2016 Low Pressure Line routing IF the truck has a lift pump with filters. This routing bypasses the factory filter head entirely, and plumbs the fuel straight to the CP3. On Duramax's, the fuel inlet to the CP3 will always be a 1/2" fitting that is horizontal and next to the FCA.
(The 2011 LML Duramax Rail Return line is a little different as it has a metal hard line you will connect to and a different connection at the inlet over the drivers rail, but the routing is the same.)
You will notice in the picture a black bent fitting on one of the vertical ports. This is the return line fitting we were referring to. Most kits use a length of 3/8th fuel line and make a big loop to connect back to the hard line in the valley, which there is nothing wrong with, some DIY'ers do prefer a clean routing, which is where the JCG Return Line Fitting Kit comes in. See below for an example installed.
But, what if you want to keep the factory fuel filter? Either you have the Fleece In-Tank Lift Pump, a lift pump without filters, or no lift pump at all, or even just want to keep it, how do you route your lines?
Similar in theory to the way you route from the connection over the drivers valve cover up to the port on the drivers rail, you will then route fuel line from the T on the JCG Low Pressure Line Kit over to the inlet on the filter head. Extra 1/2" fuel line may be required. You will then route 1/2" fuel line from the outlet on the filter head and run back over and loop into the inlet fitting on the CP3. Be sure your loops are long enough so as to not kink. Routing this way will eliminate points of leaking in the valley while still maintaining your factory fuel filter head.
The above methods are great where there is extra clearance from an aftermarket Y-Bridge Kit, but with a factory Y-Bridge in the valley, the routing is just a little bit different for the 2012-2016 model years. The factory line coming off the rail to the factory low pressure line will be reused and spun and angled to connect to the T of the JCG line kit. Doing so, eliminates a kink that arises due to the clearance of the fitting and Y-Bridge. You will route this way for either utilizing the factory fuel filter, or bypassing it entirely. Shown below is an example.
Thanks for reading, I hope this clears up any questions that may arise during your install on our CP3 Bundles with the JCG Low Pressure Line Kit.
Thank you all for the support!