View Full Version : OBS Electric Fuel System

Tom S
06-30-2012, 08:39 AM
My version of the conversion to an electric fuel system is based upon a single stock SD fuel pump F81Z-9C407-AC. This is an end view of the connector on an OEM harness

I modified the fittings on both ends to accept regular high pressure diesel rated fuel hose. A 5/16 compression ferrell was added to form a hose barb on the inlet. The stainless fitting on the left was shortened and the ferrell silver soldered on. I chose this method for cost and simplicity. There are certainly other methods of doing this with a lot more bling.

This is a close up shot of the outlet end fitting as modified.

I made up a mounting plate for the pump out of some scrap steel and I got the connector and the wire/pins from the junk yard off a Taurus and a Crown Vic to match up to the connector on the pump for a clean and secure connection.

For a pre pump filter and water separator I purchased a Stanadyne fuel manager assembly part number 33640 from Reliable Industries The photo shows it with my fittings and a Marshall restriction gauge. http://www.reliableindustries.com/catalog/STN/fm100.php

For the final filter post pump I used a Napa FIL4770 base with 1-14 threads and 1/2 inlet and out let ports I purchased if from www.fleetfilter.com It is the same as a Perma Cool or Wix 24770. I selected this as it is economical and I wanted to use the Caterpillar 2 micron filter post pump.

Tom S
06-30-2012, 08:39 AM
I decided to run Caterpillar filters on the pre pump side as well. I picked two different ones the 117-4089 which is a 150 micron filter water separator.

I also selected the 131-1812 which is a 30 micron element and is what I am currently running.

I had to modify the Stanadyne base to fit the keyway arrangement of the cat filters. I used a dremel tool and a rotary tool to cut in two new keyways. This was easy to do since the base is aluminum.

I also purchased a heater element for the pre-pump filter. The photo shows Stanadyne 34957 150 watt heater that goes in the top of the filter base and has a built in thermostat.

This photo shows both filter assemblies side by side and the two micron high efficiency cat filter 1r-0750.

I fabricated a bracket to mount the filters and pump inside the frame just aft of the transfer case. The angle bolts on the back side of the plate and then the angle sits on the flange of the frame rail.

This photo shows the filters and pump mounted to the bracket with the hoses connected.

I used ABA damage free hose clamps at all connections. These do not have slots in the band to dig into the hose. The edges of the bands also have a radius that does not cut into the hose.

Tom S
06-30-2012, 08:40 AM
A shot of the pump and filters mounted under the truck. I can hear the pump when you are waiting for the wait to start light to go out but cannot hear it at all once the truck is running. The stock mount was retained as it double isolates the pump from the frame to reduce noise. The factory lines were used and I just spliced in after the selector valve which is already plumbed in with rubber hose. The only modification I had to make was to cut back the metal line to make a smooth bend with the rubber hose while clearing the transfer case.

I decided to feed the heads at the rear the same as the stock system. I replaced the fittings at the rear of the heads with 1/8 to -4AN adapters and custom bent some stainless tube. The blue hose is Aeroquip socketless hose. The sender is a hobbs switch that triggers the fuel filter light if the pressure drops below a set level. The aluminum block is actually an air hose 3 way. The heat shielding is to protect the lines in the area of the turbo.

This is how it looks when mounted in the valley.

I reused the metal fuel lines from the stock system on the motor. This shows the point where the stock feed and return lines were cut. Compression ferrels were soldered on to form hose barbs for safety. There is clearance to the engine itself and the IPR.

I used an Aeromotive regulator that a got from www.itpdiesel.com on the return side. I reused the stock rubber fuel lines with the use of a 90deg adapter and a short section of stainless bent in a U shape. I made a bracket to attach it to the EBPV bracket on the HPOP reservoir.

More Photos
http://thumb2.webshots.net/t/14/14/3/89/4/2240389040093096422iyjCZf_th.jpg (http://rides.webshots.com/photo/2240389040093096422iyjCZf) http://thumb2.webshots.net/t/53/153/7/61/21/2551761210093096422xaMeVZ_th.jpg (http://rides.webshots.com/photo/2551761210093096422xaMeVZ)

This is how everything looks with the engine cover installed. I also took the regulator apart and reversed it to put the gauge port on the other side of the mounting point.

On all of the AN flare connections I used these Flaretite seals I got at the local hydraulic shop. They are not necessary but are there to help prevent leaks and they seemed to work nice.

Tom S
06-30-2012, 08:40 AM
I bought a couple of tools for making those AN flares for the stainless tube and also for bending the lines. The tube bender is an Imperial 464-FH-04 and the flare tool is a Ridgid 377 37 degree AN JIC flare tool. These are both awesome tools. Thanks for the suggestions Dennis@ITP

I wanted to make the electrical portion as clean and factory looking as possible. I got a couple of extra fuse boxes out of some wrecked police cars at the junk yard. I disassembled them and learned how to take the fuse box apart damage free. I then used the connectors from the junk boxes to add to my factory fuse box so that I had a spot for an extra relay and an extra fuse. The end result is that everything looks 100% factory with no odd wiring running around.

For safety I wanted a way to cut the power to the fuel pump in the case of an accident. I used a inertia switch from First Technology who also makes many of the switches of this type used in a wide variety of vehicles. I installed the switch so that it is on the ground leg of the fuel pump relay. Another method of doing this is to use an oil pressure switch which others have done. The advantage of that would be that the pump does not run anytime the key is on like when you have a scan tool connected. I chose this route as I liked the idea of having full fuel pressure at the injectors upon start up.

I also have a filter minder for the suction side of the system to replace the marshal restriction gauge. This came from Engineered Products Co and works just like the ones on your air filter except it is made for fuel filters.


Thus far I have been happy with the system. The truck runs better and has a little more zip which also showed up at the track. The Hobbs switch is set to trip if the system pressure drops below 45psi and that has never happened. The cleaned up valley is also very nice.

I may at some point make rock shield for the filters but thus far I have had no problems as they are pretty protected by the transfer case and the skid plate. The other modification that I am considering is to add a fuel cooler to the system. I have not made up my mind on that just yet and want to collect some more data on the temps in hot weather with a low fuel level.


Tom S
06-30-2012, 08:41 AM
I decided to do some tweaking on my fuel system yesterday.


I wanted to add AN fittings so that the whole assembly would be easier to R and R and not have to deal with hose barbs but could not find what I needed to work with the 5/16 fuel lines. I used -6 AN fittings and cut off and drilled out the 1/4NPT end to accept a 5/16 bent steel line. I then silver soldered them in place and added a compression Ferrell on the and to create a barb.



I installed the filter minder that I had been planning on installing for some time now and added a temp sender in the pre-pump filter head. I am next planning on doing some experimenting with a fuel cooler so I wanted to have a good way to measure the fuel temps going into the motor.


Here is an overall shot of the modified assembly

Tom S
06-30-2012, 08:42 AM
I got the fuel cooler stuff finished last night. Unfortunately Derale sent on that has a small leak in it at a stopping and starting point for the TIG weld. I have a new one on the way.

http://inlinethumb04.webshots.com/40259/2493296440093096422S600x600Q85.jpg (http://rides.webshots.com/photo/2493296440093096422RfjgfJ)
I have a bypass installed for right now. I also wanted to do some testing with the bypass installed to evaluate the supply temps without a cooler.

http://inlinethumb39.webshots.com/41638/2670701760093096422S600x600Q85.jpg (http://rides.webshots.com/photo/2670701760093096422RfSRDR)
http://inlinethumb06.webshots.com/42309/2576418710093096422S600x600Q85.jpg (http://rides.webshots.com/photo/2576418710093096422shiIyk)