My DIY OBS fuel system using 6.0 parts.
I’ve been considering an electric fuel system for quite a while now, and finally decided to bite the bullet and replace the mechanical setup. After seeing prices in the $1500.00 range, I started doing some thinking on building my own economical system. I wanted a system that would uses parts that are easy to find, not something where my truck is immobile while I wait for a one-off part, or a hard to find filter. For a pump, I decided on the 6.0 PSD HFCM (Horizontal Fuel Conditioning Module) which contains the pump, a filter and water separator (older models also have a fuel heater.) A fatal flaw with the HFCM is that the fuel supply entering the water separator is unfiltered, so any debris from the tank can clog up the water separator, and cause the “water in fuel” light to turn on. To prevent such a calamity, I had an old filter head laying around, which a WIX 33358 filter fit onto. The 33358 is used in truck, farm, and industrial applications of Cummins, Deutz, and Volvo engines and has a 10 micron rating and 6-8 GPM. For final filtration, I opted to use a modified valley filter from a 6.0 PSD. If I have a filter fail and leave me stranded, I should have no problem finding a replacement (one should carry spares anyway.) Pressure regulation is handled by an Aeromotive diesel-rated marine regulator #13114. The parts for the system cost me around $600, shopping around on ebay for the major components, and fittings and hose I picked up locally.
Major components, regulator, pump, pre-filter, post-filter.
The component I had to do the most work to was the 6.0 valley filter housing. First we want to maintain a regulated return, so the housing’s regulator has to be junked.
Remove the regulator cover and components
Do not remove the air bleeder orifice or you’ll lose a lot of fuel back to the return line
The air bleed also allows the fuel pressure to fall to zero after about 30 seconds after shutdown, which is a good idea if a potential injector leak occurs
Drill the regulator seat opening to 7/16” and tap with ¼ NPT tap.
In keeping with the “keep it simple” idea, I decided to eliminate the O-ring boss (ORB) fittings the filter housing uses and drilled/tapped everything to either ¼” or 3/8” NPT. This will reduce the footprint of the housing in the valley, and less connections=less potential leaks.
After all drilling and tapping is complete, clean the housing thoroughly with brake cleaner. Install a ¼” NPT plug in the hole where the regulator used to reside. Re-install the test port plug.
Re-install standpipe and regulator cover. The oil filter section of the housing can be cut off, leaving the webbing as a mounting point. Some basic fittings and hose barbs complete the plumbing. Slight modifications to the regulator bracket are done to mount it to the housing.
1 Fuel return from heads
2 Return to tank from regulator and air bleed
3 Fuel supply to heads
4 Incoming fuel supply
Now we are ready to take the truck apart. Remove valley cover (if applicable.) Place a catch pan under the truck and open the water separator drain to drain the filter housing. Disconnect the lines and unbolt the filter housing. Remove the intake Y. Rather than fighting with the banjo bolt one last time, I used a screwdriver as a chisel and broke the lines off the banjo fitting.
Unbolt and remove the pump, clean up spilled fuel. Apply sealant to a 7/8” freeze plug and install in valley hole (sorry, no pretty billet block-off plug here
I then started putting in new supply lines to the back of the heads. I figured to maintain the stock flow configuration, since air should rise to the front due to mounting angle of the engine. I also wanted to keep one line feeding each head for maximum parallel flow, I’ve noticed some kits run the heads in series
I ran ¼” line to a 1/8” NPT barb fitting, and a nipple and a 90* to give it room to clear everything. I left the 45* fitting in the head, since it seemed fine. 96 (and earlier?) have a 45* fitting, and a 45* rotolock fitting adapter. The 97 has a 90* rotolock fitting, which apparently has to be cut to remove (or remove the turbo.)
I couldn’t do anything on the passenger side with all the piping in the way, I couldn’t get anything to fit without bumping into something. I resorted to reusing the stock line section clamped to a new line. It’s leak-free, but I will change it to something better in the future.
Using some 1-1/4” angle, I fabbed a simple T bracket to support the filter housing. It mounts to the original filter housing holes, and has clearance for 3” plenums. The bowl can even be mounted low enough to clear the valley cover, if re-installed.
I added a few more 90*s to make connections to the hoses with less chance of kinking. On the head return line tee, the 90* flare fittings are re-used from the old filter housing.
Install the filter housing, connect the lines.
Under the truck, I installed the pre-filter. I know, you’ll say it’ll get hurt under there
It’s higher than the bottom of the fuel tank, it’ll be fine. Besides, I’d rather have this tin can filter dent instead of some pretty plastic bowl cracking.
Next was the pump, mounted to the frame rail, connect the supply/return lines, and run power wires.
Wiring was pretty straightforward using existing inputs. I used diodes to isolate the inputs from each other (so the oil pressure wouldn’t make the WTS light come on, etc.) With this circuit, the pump will run when the Wait to start light is on to pressurize the system, run the pump during cranking, and whenever there is oil pressure. I removed the “fuel filter” lamp, since it would be on all the time.