Bottom Line Up Front (BLUF): After implementing the voodoo described below, I now have an OE JK fuel pump module, without the OE float assembly and instead with an ISSPRO 8" fuel level/float unit, a M54 65 psi regulator in the pump module (OE is 58 psi), and a return line from EFI Systems Pro, and it all functions perfectly...without any 'data' nor a computer.

See post #13 for a deep-dive into how the main valve works.

See post #14 for a step-by-step fuel pump swap without dropping the tank

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Original post -

ok - I need to fully understand what the big mongo valve 'does' for my 2014 JKU fuel system - pls check my brain on the below pic. Also...is there really no fuel return line from the engine directly to the tank? - does (what looks to be) the 'return' line really just go direct to the charcoal canister...and then...to where? Is the return line not actually full of liquid gasoline, but vapor?

Anyway, pls confirm the descriptions in this pic - would help me a lot -



Thanks
- Sam

 

lemme ask it this way - any reason(s) I couldn't plumb the tank as shown? 1) Main filler vent to the filler neck. 2) Main tank vent to charcoal canister 3) Purge line to throttle body via purge valve 4) Fresh air intake 5) ...don't reallly know why these two valves are connected - why not just seal them off?...but otherwise I'm intending to just leave them connected to each other.

Again this is an off-road toy, and I want it to be decently 'clean', and I have charcoal canisters that work great as shown...so I'm thinking I can plumb in my '14 tank as shown and have it all work/vent properly, ya?




I still need a dedicated fuel return line to enter the tank someplace, but that's a different issue...

 

I wish I could help with this one but I don't have the answers. I am subscribed now though cuz I'd be really interested to hear the explanation as well.

 

ok - I talked with my EFI guy Scott at EFI systems Pro, and he thinks the above diagram would work good, providing a dedicated return line is incorporated, and I'll use this -
https://www.efisystempro.com/fuel-tank-return-port-kit

So, I'm going to scope the rollover valve and see what flows into what, but the above is apparently a decent way to run these tanks without the OE anything in control . It'll be a while, but I will definitely post back with the results.

- Sam

 

to follow-up to my thread, here's info and pics of how I got 'access' to the fuel sending unit assembly through the floor of my 2014 JKU with no need to drop the tank, and cover, and armor, and, and, and. My build is a bit different than others but the info should be useful either way.

I made three access holes in the floor, none of which cut into any of the subfloor crossmembers/bracing. I am using the OE fuel pump system but not the fuel level float/sender - I'm doing stand-alone ISSPRO fuel level float/sender, and I added a return line for the Sniper EFI -


Specific location directly above the sending unit -




looking 'forward' -


looking to the p-side corner -


In my case I'm going 'computerless', so I installed an independent float unit and return line for the Sniper -


Float inside the tank -




And an access hole for the main vent -




Hope these help
- Sam

 

so to confirm, the small port goes to the fuel evap/charcoal canister system, and the big port ultimately goes to the main fuel filler neck vent, correct?

...I'll be satisfied with a "don't know for certain but yes that is how I understand it"...

 

Staying with the above thought process, I pressed ahead, and wanted to update this thread with recent additional info. First off - just fired up the Jeep a few days ago, and it all went great. Had a couple more big milestones yesterday, the big one regarding the gas tank and my evil plans to 'simplify' it, all of which appear to have worked.

To recap, I semi-gutted the OE fuel pump module, removed the fuel-level components/wiring, and replaced the OE fuel pressure regulator with one with a slightly higher psi rating (65 psi, compared to the OE ~58 psi). Then I drilled a hole and added my own fuel level/float unit, and drilled another hole and added a return line. Then yesterday I drove it to the gas station and confirmed I can 'fill 'r up' like a normal machine - gas fills to the top and the nozzle kicks off normally with no gas pouring out the spout. The gas tank doesn't leak anywhere, and that was the big one; the return line and fuel float ports are bone dry, so the seals in the respective kits are apparently working great.

Fuel pump module access hole is welded/sanded smooth/painted, and ready for the cover -



...gas tank filler tube and vent are connected - it's a 1" NPT steel bung welded to the filler neck, then a 1" npt x 5/8 hose adapter, and 5/8 hose down to the big vent port; used Gasoila E-seal to seal the filler neck vent fitting -


Fuel pressure regulator voodoo. Before dropping the body on for good I was able to test my fuel system for leaks, flow etc., and discovered some interesting info. The (Holley) Sniper has it's own fuel pressure regulator, set right about 63 psi, but I didn't know that the OE JK fuel pump module also had its own internal regulator, apparently set at 60 psi. When I activated the pump, the high pressure side filled up to the Sniper and displayed 58 psi on my mechanical gauge...but...I was not getting any flow out the return line. The reason was because the OE regulator pops open before the Sniper regulator does, which if left alone would essentially turn the Sniper into a 'dead head'...which IIUC is how the factory did it, too. But, because this Jeep will see extreme conditions (including heat soaking), I very much wanted an active fuel return line to continuously circulate cool fuel through the lines and throttle body, eliminating what little heat possible. So, I needed to figure out a way to alter the OE regulator to allow the pump to make more pressure...thus allowing the Sniper regulator to function.

...a'ite - so with that in mind, I pulled the module back out, took it apart all the way down to the pump and regulator (non-serviceable unit my ass - just need 5 hands...), pulled the regulator, and removed the pressure spring. I 'thought' that removing the spring would enable the pump to flow at a higher pressure...but instead it reduced pressure down to about 30 psi.
Here's the basic fuel pump module -


Separate the spring-loaded top half, remove the pump housing, and then with 5 hands separate the filter assembly from the bottom (this was fun) -


this is what the OE Jeep (2014) wrangler fuel pump pressure regulator looks like -


and the pump itself, with the only part numbers I could find being REP500 07-04










Initially I thought I could increase the pressure by removing the pressure spring and remove the valve, but after cutting the end off the regulator and removing the spring the valve wouldn't come out...so I just left it there...






Reassembled and reinstalled everything, activated the pump...and now was only getting ~30 psi, and of course no return line flow. So, apparently (obviously) the spring is necessary to create pressure...but it's a spring...and I need just a little bit more pressure...so if it were a 'tighter' spring it might create more pressure...so with literally nothing to lose...I pulled it all apart, inserted a nylon washer to fill in some of the gap to the plunger, and crimped the housing closed so the plunger couldn't move at all...thus forcing the regulator to be at 'maximum'. Hey it's not like it's gonna blow up...


Slammed it all back together, hit the pump, and with a fully 'closed' OE pressure regulator the system filled all the way up, and made enough pressure to open the Sniper regulator (horray!), and fuel was flowing out the return line (horray!), and the gauge was showing about 64 psi - all now regulated by the Sniper system...which is exactly how I wanted it.

So, learned a lot about how the OE system works...but I'm not really a big fan of smashed-together pressure regulators...and while it would probably function as-is forever...I looked into regulators that might have a higher psi rating that if left alone would accomplish the same overall functionality as I've achieved...and I found them. DeatschWerks make 4 regulators, rated at 65 psi, and they are all identical to the JK unit, the differences between them (according to their tech folks) being the application they're for. Ordered/installed this M54, and it provided more pressure than the stock JK regulator, thus enabling the Sniper to function as designed. Boom.

https://www.summitracing.com/parts/dwk-6-45-m54

...high pressure fuel filter is mounted in place on a removable bracket allowing it to hover just above the sending unit while also being neatly under the trap door, which I will raise up just about half inch to give plenty of clearance, both easily accessible from the floor hatch - just remove the right-rear seat and the hatch is right 'there', which is a LOT less work than dropping the tank I promise you -






removable bracket to allow for removing the sending unit - works great -




removed a bit more from the floor -



and will clearance this lower part just a bit more -


Installed a ISSPRO 8" fuel level float/sending unit (RA9508) - sanded the tank at the seal to smooth it out/help eliminate leaks - put Gasoila E-Seal on the threads and cranked the bolts tight into the collar, and it acts like studs and won't fall out if I ever need to service the float unit -











Next - return line. My Holley Sniper EFI needs a return line, and I got this nice return line kit from EFI Systems Pro - same place I got the Sniper from - great place and great tech support -



Float and return line installed - little heat and the OE plastic return line tubing slid right over the new fitting, and used an EFI clamp to make sure it stay's put -



I did have to trim the tops off of both the 5 mounting studs and plastic standoffs in order to not hit the bottom of the cover panel -



So now I have an OE JK fuel pump module, without the float assembly, and with a M54 regulator, plus an ISSPRO float unit and return line from EFI Systems Pro, and it all functions perfectly.

- Sam

 

Also, found this really slick 3/8 aluminum fuel fitting that replaces (in this case) the output fitting of the OE plastic wrangler gas tank sending unit. A guy on Irate made me aware of these, and I already have it installed. This is an aluminum, internal double o-ring EFI fuel fitting which appears to be a specific replacement for the weak OE plastic fittings -

Evil Energy 6an - 3/8 fuel fitting - https://www.amazon.com/dp/B07GB2R77C...sin_title&th=1

...and the 6an to 5/16 hose fitting to complete the package -
Evil Energy 6an - 5/16 hose fitting - https://www.amazon.com/dp/B09494FV4N...fed_asin_title

As far as I can tell this fitting attaches to the plastic output tube on my 2014 Wrangler gas tank perfectly - secures nice and tight to the stop lip -

 

ok - Just finished 4 day shake-down run in Moab, and the Jeep worked great. Wanted to update my own thread with more info, and a question.

First off, 'fuel-filling' operation works perfectly - pull up to the gas pump, stick in the nozzle, squeeze the handle, and the tank fills up quickly and shuts off perfectly - no problems filling the tank. Also, fuel pump, pressure regulator, float, and return lines all work perfectly. So that's all great.

Bottom line is I'm trying to confirm which port to use to vent/purge tank vapors to a charcoal canister, but not liquid fuel. To that end I'm hoping someone can simply confirm what this port (circled in orange) is specifically for? I think it originally goes to the filler neck - not sure why but maybe that is how the factory routed vapors to the charcoal canister? Is this the tank pressure/vapor vent, that goes to the charcoal canister which is purged via the throttle body? And...if I were to fill the tank and tilt it back, would fuel simply 'flow' out that port, or is it a 'pressure' vent that only opens at some pressure build-up in the tank or vacuum on the output side?

 

my overflow valve broke on the right side and I too am wondering if it could be just capped off or if you ever got an answer