JMS Fuelmax Install with Photos - 2nd Gen Supercab

[FenixAmmo]

GooseTuned says I need the JMS FuelMax to go any further with the truck and I noticed there was only one installation thread, and it was for crew cab trucks, so I figured I should add another.

My truck is a 2018 supercab with the following performance mods:

Fresh OEM long block with 1,500 miles
Garrett Powermax turbos
Full Race manifolds
Cobb dual intake
AMS inlet tubes
Full Race FMIC
Turbosmart BOV
Stainless Works 3" downpipes
SPD trombone resonator
Custom 4" dump exhaust
IDE 1050cc port injectors
Full Race radiator
Full Race transmission cooler
Radium Engineering catch cans
Cobb Accessport with GooseTuned tuning

Lots of other mods but those are the engine/performance items that matter. I'm running 100% E85 fuel 9 months of the year and 93 octane over the winter. After the addition of the Powermax turbos and manifolds, Goose said I had hit the limit of fuel flow and suggested the JMS. Let's get started.

The JMS Fuelmax piggybacks in between your fuel pump driver module (FPDM) and your fuel pump fuse to increase the voltage as the throttle pedal gets pushed down further. JMS recommends you locate the unit INSIDE the cab. You need to run a single wire to the throttle positions sensor underneath the driver's side footwell, and, you need to run the main harness out to the FPDM. One way or another, you'll need to route a wire from inside the cab to the outside of the cab.

The only other installation guide for this unit recommended unbolting the bed from the frame so the bed can be slid back enough to route the wiring through a factory grommet on the crew cab trucks. I was absolutely determined to avoid this at all cost given the number of bed bolts that break during disassembly, and because I have a bed cage that would have added at least a couple hours to this job. On Supercab trucks I am happy to report this is 100% NOT REQUIRED.




As you can see above, the FPDM is located on top of the crossmember toward the rear of the fuel tank, just to the left of the brake lines. There's a yellow tab you unlock and pull to the right first, which then allows the connector to pull free. The JMS harness plugs into the FPDM, into the OEM harness, and then gets routed up over the fuel tank where you'll connect it to the JMS unit once you get the harness fed down from the cabin area.

Simply connect the harness, and then feed the tail end up over the fuel tank and let it hang down for now. You'll want to leave the harness loose for now until everything is routed properly.

 

[FenixAmmo]

On supercab trucks, there's an air vent directly behind the audio processing module located behind the rear seat on the driver's side. There's also enough room to locate the unit itself in this space, and, a factory grounding point within 24" making it a great spot. It also doesn't impact your storage under the seat, or behind the rear passenger' side seat. You can see the unit already installed here; there's enough room to squeeze it between the audio processing unit and the backseat.


The air vent will be accessible by removing the audio processing unit and the subwoofer first, and then pulling back the carpet trim on the back of the cabin. You don't need to remove the carpet entirely; just peel it back about halfway as shown.




I routed the Fuelmax harness down through the top right hole in the vent and kept feeding it down until I could see the connector drop down in the space between the cab and the bed. You should see it near the rear cabin mount insulator and the rear fender stay.



The wire may come out of the loom as you do this because it's a tight squeeze through the vent, but you can simply fix this later. Using this method, I DID NOT have to remove the bed bolts which was very important for me given how often they break on removal, and, because I have a bed cage.

Most of the hard part is done now. Simply route the JMS harness along the frame and toward the fuel tank area. Once you connect the harness to the FPDM pigtail harness, you can go back and zip-tie the harness to a factory harness located in the same area.


I suggest keeping one of the connections near the FPDM, and the other harness connector inside the cabin. The JMS harness has three pieces, so you'll see what I mean once you start routing everything.

 

[FenixAmmo]

Once you have the FPDM harness completed, you can move on to to throttle pedal activation harness. The best way to route this is underneath the sill plate where there's a convenient wire tunnel.

Remove the sill plate first.



Then remove the trim surrounding the hood release.

You do NOT need to completely remove the trim piece toward the back; you can unclip the lower part and pull it away enough to route the wiring.


The throttle position sensor gets unclipped, a pigtail harness connects in between the sensor and the harness, and then a single wire monitors the throttle position and sends the data back to the JMS.


Next, route the wire up under the dash and zip tie to other wire harnesses as necessary to keep it securely out of the way.

 

[FenixAmmo]

At this point you're pretty much finished - the rest is simple reassembly of the various components you removed. I zip tied the remaining harness to the JMS unit making sure the connectors weren't strained on either end.



The last connection to be made is to ground. JMS ships this unit with a ridiculously small grommet connector, so I cut it off and added a new one large enough to fit under the factory ground bolt located next to the seat latch.



You're done!

Goose provided me with the initial recommended settings shown below.



Overall, the install was very easy. From start to finish, it took about 2.5 hours and that including stopping along the way to take pictures, rerouting the harness here and there, making coffee, and vacuuming out a fair amount of sand from under the sill plate.

 

[dillard09]

Very nice install. Similar to how I did mine on the SuperCrew. Thanks!

 

[Nex]

Nice write up.

 

[Tomkirkland4]

Very helpful!

 

[1BAD454SSv2]

Did you have to install a larger fuse ? In stock fuse location ? I have this on my 2010 6.2 and whipple with smallest pulley .