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Moses...We spent another great extended weekend in the Black Rock with the CJ-8—except for one thing.  On a day trip to High Rock Canyon, Jeep started to misfire and even backfire then just stopped running.  We monkeyed around with 100 possible issues but soon learned only 20 psi at fuel rail.  Would start, but give gas and die, or let idle and after a minute pressure slowly drops and engine dies.  Then after further testing, pump stopped running and zero pressure. Ran a dedicated hot wire to pump hot lead near inlet and nothing...would not run. 
Had a spare external pump, and we cannibalized from 4 other Jeeps along, just could not make it work.  Needed additional fuel lines and fittings, hose clamps, etc.  We even back flowed the filter alongside the trail with what little lines we had and all sorts of black puke came out...Captured the fuel in a Coke bottle and saved it.  Lots of black particles settled to bottom...So I suffered the indignity of being towed 60 miles over very silty, talcum power trail, near zero visibility (since strapped to a tow rig), and since we aired up the front tires to make steering and towing easy, a VERY rough ride. 
Hauled the CJ-8 to a friend's area ranch, and with help from their well stocked shop, I was able to cobble together a patch.  Hose clamped the spare pump to frame rail and routed power and supply lines.  What a pain!  Taped a fuel pressure gauge to driver's mirror to monitor pressure on the long drive home.  As for pressure, the engine idles at about 38 and bumps up to about 41 under acceleration, but no more.
So plan is to cut a hole in the rear tub for future possible fails.  The big question is, first, what replacement pump and are there psi values for that?  Or does the regulator handle all that?  Wonder whether more PSI will help run better. 
This is still a cold mother on start up—before doing some work, it often took 3 or 4 times to get to run.  After temp sender fix, starts on 2nd try.  Very likely failing pump contributed to recent performance issues.  New pump will tell.  And once the hatch is cut, I will carry a spare pump! 
Cutting the hole looks pretty straight forward.  About 1" clearance, so start small and work outward.  Don't want to cut the supply or return lines...In any event, will have to drop the tank to clean and see what's inside...It just might be easier to locate the access panel with the tank still in vehicle.
Any thoughts on pump ratings, regulator or???   With those Ford 302 V-8 injectors, what PSI do they like to run properly?  Are there any specific advantages to converting to a single fuel line supply system?  I am SICK of dealing with intermittent fuel delivery issues and am now more than ever committed to designing a long-term fix.  I wonder if the injectors are fuel starved?



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Interesting trip to a favorite haunt, the Black Rock/High Rock country!...Some background on Mark's CJ-8, this vehicle has been featured at the magazine in HD videos with its Hewes Performance built 4.6L stroker six.  Mark had a Mopar EFI Conversion on the original 4.2L inline six, and he moved that equipment over to a fresh 4.6L stroker long block.  (Click on the link to enjoy the HD videos detailing Mark's engine and the CJ-8!) 


Just prior to the start of the forums, Mark and I talked about tuning issues, and there was a hint of fuel supply troubles from his symptoms...The engine uses the PCM that comes with the two-rail (1995 4.0L prototype) Mopar EFI/MPI system.  The only modification to his engine is the use of Ford 5.0L V-8 injectors, discussed at the magazine site, to accommodate the added cubic inches of a stroker motor.


Mark, sounds like there is a lot of debris in the fuel tank, and your plans to flush the tank are wise.  Having quick access to the fuel pump is a good idea, too.  As for the two-rail versus single-rail EFI, you are fine with the two-rail as long as the return flow is unrestricted and the fuel regulator at the injector fuel rail works properly.  The "normal" pressure for your Mopar EFI, which is essentially 1995 Jeep Wrangler 4.0L off-the-shelf parts, is 31 PSI when running at an idle and approximately 39-41 PSI during cold start cranking.  Your low fuel pressure from the pump could explain the recent cold start troubles, as you were not able to muster the factory 39-plus PSI during the cranking mode.  See my fuel pressure and tuning details at the magazine for specifications:


http://www.4wdmechanix.com/Jeep-Fuel-Pressure-Requirements.html [see details and my pointers on use of the right hose types and clamps for this EFI system.]


http://www.4wdmechanix.com/How-to-Tuning-the-Fuel-Injected-Jeep-Inline-Six-Stroker-Motor.html [i just added some updated tuning information at this URL page...Also see my recent forum topic posting on "Jeep 4.6L Stroker Inline Six Camshaft Choices and Tuning".]


Again, the stock 1991-95 4.0L two-rail EFI/MPI engines operate at 39-41 psi during cranking and 31 psi with manifold vacuum applied at the pressure regulator.  If you're now experiencing 41 PSI going down the road, and if the stock pressure regulator at the rail is not defective, make sure the vacuum hose to the fuel pressure regulator (at the rail) is attached to the correct vacuum source and pulling vacuum properly.  Connected, the vacuum line at the pressure regulator should keep an idling engine at 31 PSI, read at the fuel rail test port.  Disconnect the vacuum hose from the regulator with the engine at an idle: The rail test port pressure should bump up to 39-plus PSI.  An adjustable regulator is available from HESCO for fine tuning if necessary.


The Ford 302 V-8 injectors (F1TE-D5A) flow 24.25-pound/hour @ 39.15 PSI, which is why this is the optimal injector for a two-rail Mopar EFI system on a stroker inline six.  You get true 24-pound/hour flow availability, which works well for the stroker buildup of a 4.0L into a 4.6L!  So, Mark, you have the right injectors, and the pressure you're currently getting sounds like a close match for the Ford injectors.  Your fuel supply pressure, regulator pressure and injector flow rate should each work with the Mopar EFI Conversion's PCM.


If you run the correct pump pressure and volume, regulator setting and injectors, using the right hose and fitting types, clamps and so forth, you'll be fine.  Starting should get easier with a new pump.  As for pump pressure and volume, the supply pump that came with the Mopar system is typically 70-90 PSI rated with around 36-40 GPH flow rate.  Again, the excess pressure returns to the tank on this two-rail system.  (Make sure there are no restrictions on the supply or return side lines!)  HESCO sells this pump as do many others, it is a common aftermarket design that simply provides enough pressure and volume to "over-supply" the system.  The key is the pressure regulator, which directs the excess pressure/flow volume back to the tank.


Be aware that the PCM controls fuel flow on this system.  Don't get creative and route a wire from the ignition hot lead directly to the pump.  You must use the wiring and relays supplied with the Mopar EFI kit, as this emulates the stock 1995 Jeep Wrangler 60-way PCM functions.  If necessary, revisit the wiring schematic that came with the Mopar EFI kit to assure that the fuel supply gets triggered by the PCM—which is not simply a "key-on"/"key-off" fuel pump.  The PCM controlled fuel supply is for safety and performance.


I have several articles at the magazine relating to installation of a Mopar EFI kit, both the two-rail and the later single-rail types.  As for single- versus two-rail differences, the single-rail design uses higher rail pressures (see my article links), adjusted by a regulator atop the fuel pump module at the fuel tank.  Mopar Performance's later EFI conversion kit supplies this regulator, modified to fit in-line on the fuel supply system.  If you run a single rail system's higher rail pressures, you need different injectors to get precise 24-pound/hour flow.  Your current injectors with the additional pressure could over-fuel the engine, producing 27 or so pounds/hour flow at the single rail's potential 50-plus PSI pressure.


Since you already have these injectors and a two-rail system, I would stick with it.  There is no inherent problem with the two-rail design.  You can mount the replacement fuel filter as shown in the EFI kit's instructions or as seen at my magazine articles on the EFI conversion. 


Making a hole in the tub floor is not a bad idea, although you need enough room to remove the hoses from the pump and safely handle the wiring.  As a result, this would not be a small hole, as you would need to get your hands and tools in there.  For an alternative, consider relocating the pump to a safe, outside frame rail mounting point near the tank.  Readily accessible from the side of the vehicle and out of harm's way, guarded with a custom skid and brush plate if necessary, this could be a solution...Share your thoughts, Mark...


As a footnote, the fuel filter can clog readily.  Make sure the fuel cap seals from dust on those alkaline roads and the Rubicon Trail!  Change the fuel filter regularly, and carry a spare...Get that tank flushed and check the tank pickup for debris as well. 


Great to have you posting at the forums!



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Moses, thanks for all the helpful suggestions and for a fine reference library of priceless info.  The back story is when i first did the mopar efi conversion on the 258 i used the external pump and a pre and post filter set up.  The tank outlet feeds from driver side, so the hose exits tank above the exhaust and travels over to the passenger frame rail.  Near the upper cross member I installed the pump and filters, securely mounted.  Problem was over time the supply line would become dry and crack, causing untold fuel supply issues.  Sleeving it all with some radiator hose didn't help.  Than as now, the pump is  powered per the install directions, relays, etc.


After consulting with Lee Hurley, he suggested upgrading to an intank pump, which i did.  Cut a 3" round hole in top of tank, which is an Aero 33 gal mammoth.  (also a tail dragger on some steep departures).  That pump (model unknown but have pix) bypassed the old tank pick up and exited tank at top thru the pump then routed to the OEM mopar fuel filter (the one with 3/8 and 5/16 ends).  All worked well for about 2 years, then the old problem of 'i smell gas' comments.  Discovered where we mounted the pump into tank it is just a thin material.  We tapped the screw holes and siliconed it up tight, but after a few good whacks on the tank, the top warped a bit and compromised the pump to tank seal, causing spillage.  This was only a real problem when tank is full (lots of $$) and on off camber situations, so i let it go and on the to-do list.


Six months after the stroker build my mechanic took her in for some tweaks because of pinging under load.  That was addressed, but started to experience very rough cold starts.  Have to let it idle for 10 minutes until the loop changes, then perfectly drivable.  Sometimes it would take 3 or 4 starts to keep it running.  Anytime during these events, give a little throttle and it dies.


Fast forward to last weekend.  Still rough cold starts, multiple tries to get running, but all seemed well after warmed up.  We were 60 miles north of a gravel road, far and deep into the remote section of the NCA when i felt a sputter, then a backfire.  Oh, ok, keep driving.  Got another 1/2 mile and she stumbled and died.  After several hours, yes hours, of trying this and that to ID the problem, the screw on pressure gauge told the whole story.  Pump would struggle to get to 15 or 20 psi, then as noted above, would die.  Fuel starved.  We ran a dedicated hot line to the weatherpack power plug for pump near tank, and it would not run at all.  I do carry the old in-line pump but we gave up after trying to get proper fittings, clamps to graft it inline.  So a very long and bumpy ride back to the gravel road, then another 30 miles to the ranch where we were able to cobble together parts to drive back to reno.


Yesterday we pulled the tank with interesting observations.  That will be my next post.  Trying to paste a link to parts and photobucket w/ no luck.  Will post Part II in an hour or so... 



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Part II


ok, tried to paste a link to photobucket pix-- no go.  is there a trick?


The last couple weeks before the pump died, at key on when the computer flashes a fast 12 volts to the pump, when it powers for a moment, before it was relatively quiet, but lately it gave a real growl that one guy said he heard from 50' away.   Even at idle, the pump was distinctly loud all the time.  Approaching death throes?


Before we dropped the tank we used the temp pump to suck out the remaining fuel to make it easier to handle.  Pumped out the fuel thru a Mr. Filter into a sceptor MFC.  Extracted about 9 gallons.  Inspection afterward of the Mr. Filter showed some debris, milky looking unknown stuff that pooled on bottom--- water.  The Mr. Filter will separate particles and water from gasoline.  So we know there was water in tank and likely ???  The metal chips and debris visible and removed with a magnet were not rusted, but clean, fresh bits.

When we removed the pump the pick up sock had some grime but not much.  Have pix of all this.


We then bench tested the pump direct to the power terminals and yes, it is dead.  For sure.  Removed the pump itself from the assembly and am now looking for a replacement.  Mopar/jeep PN 52018391P looks like the ticket. (research shows it's an internal pump for 94-95 YJ/XJ).   Is this sufficient?   Also looking at the YJ fuel pump/sending unit module but the ones offered from gen right are for a HO application.  Will likely pass especially since i already have a working dedicated sending unit that works with the CJ gauge. 


To remedy the sealing of the pump to tank area, plan to first have tank hot boiled, then cut a larger opening in top and have a friend tig weld on a larger round, 1/4" thick plate.  This will be opened in center to allow pump to drop in and tapped for the screws.  This larger surface area may eliminate cracked seal.  Since the underside of the plate will be exposed to fuel, etc, am worried about rust, so maybe we can score a piece of stainless, but its hard to work with.


We also measured from tank opening to bottom of tank 13" exactly and measured the pump assembly-- 13"  we can see where the sock was making contact on bottom of tank-- movement actually scuffed up a small patch of the tank floor.  When we installed it last time, we made sure there was at least 1/2" clearance.  It now appears hitting the tank on obstacles has pushed up the bottom making contact with the pump sock and maybe even the pump itself.


So once a suitable replacement pump is obtained, and we hope to re use the mounting assembly, etc, we will make sure it is at least 1" off the floor then button it all down.


Since i have three spare mopar style external pumps will plumb in a back up delivery system.  These pumps, assorted fuel lines, filters, fittings, clamps, etc were in a trail bag i left home for the trip-- thinking it runs OK, so no need to take. Jeep lesson #5291.  Often times think we should tow a spare CJ along just for parts!  From the old 'straw' port on driver side of tank, we plan to bend up some dedicated hard brake/fuel line and exit tank, wrap around the front corner and on the forward upper mounting tab for tank, install the external pump.  have not decided if need hassle of a pre-filter. (suggest a PN?) From there more hard line at pump outlet and bend over to pass frame rail where i use a YJ style fuel filter and frame  mount.  At this point the hard line will be capped off.  Power to the back up pump will have a similar weatherpack plug capped off also.  Should the in tank pump ever fail, i simply move power over to the external pump, and some fiddling with connections to plumb it into the filter. 


Would really like to find or ID a better way to make fuel line connections.  Wish list includes rather than rubber to metal and hose clamps (i use the EFI rated clamps), but some sort of quick disconnect couplings.  For example, changing the fuel filter on my Chevy truck is a snap--unplug lines and plug in new filter.  This would make it a lot less messy and easier.  Suggestions?


Next is to find an electrical PSI gauge so i may monitor fuel pressure from the cab.  As it is now, i screw the gauge onto the schrader valve and with an extension hose, pass under hood and just duct tape to drivers mirror. 


Will also consider, since its all getting redone and with fresh lines, a new fuel pressure regulator.  A friend has several, so why not?


So the questions for the day include a proper replacement pump.  I'd like to reuse the support and top flange pump assembly.  The YJ module is $$$$$ and cannot use the sending unit feature with out spending more $ to retrofit the gauge. 


then whether to use hard brake line or fuel line.  is there really a difference.  Then locate a tool to properly bend it.  Then the fun task of reinstalling the tank.  One really needs baby hands to get to the tight upper fittings. Am still on the  fence for an access panel.  we marked the underside to drill a pilot hole should i ever elect to open it wider.  Or just do it now...dunno.  That depends on whether i can use the existing pump mount/flange which is round, compared with the YJ square design.


will post up more as i think of add'l issues.



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Hi, Mark...You have been busy!  Regarding your photo bucket links, I simply copied and pasted the links from your Email...Below are your photo bucket links and definitions for the shots.  I have answered your post questions below these links, so scroll down further:



the temp fix


pump pulled from tank



bottom of pick up sock






showing tank with sending unit and pump removed and related openings.


detail of the round plate covering pump opening and pump assembly



gotta find two replacement gaskets like this for each component



[End of Mark's photo links...]



Sounds like your recent tune and cold start/warm up problems have been the fuel pump/supply.  Your Mopar EFI two-rail system is a prototype '94-'95 YJ Wrangler, and the PCM is looking for 39 PSI during cranking and 31 PSI at an idle after startup.  (I talk about that in my earlier reply to this topic, see above replies.)  I believe this could also be the cause of your "ping" issue, as the engine has likely been fuel starved for some time...Keep in mind that fuel pressure alone is not enough.  You also need fuel volume, which I described earlier. 


Sounds like your reasons for not using an in-tank Mopar OEM fuel pump module is cost and possible fit issues.  Also, you mention tank depth.  On that note, one inch off the floor is plenty; if you raise the pickup too high, you will be unable to access a considerable amount of the tank's fuel.


You have several Mopar EFI kit remote mount backup pumps (presumed to be 70-90 PSI and 36-40 gph flow according to HESCO).  Why not do like off-road racers: Mount a gang of these pumps, two or three, whatever you prefer.  You could run permanent fuel lines and electrical wiring to this fuel supply "system". 


Using a switching system, you'd be able to quickly switch over, even on the fly, from one pump to another!  You can use manual switches with relays if desired, each circuit fused for electrical safety and integrity.  The pump activation signal would be the PCM wire lead that currently feeds your Mopar remote pump.  You'd want to wire the switching so that only one pump would activate at a time.


Although there is some discussion about vibration and steel lines causing cavitation, I don't believe you will experience that kind of trouble with a two-rail EFI system.  There is always fuel flowing back to the tank with a two-rail EFI system, and vapor lock is virtually impossible with this arrangement. 


I have run steel lines along the frame rails (see my magazine article for some details), using EFI grade hose and fittings at the flexing points: the tank-to-frame section and the frame to engine connection at the front of the vehicle.  Steel double-flare lines, high pressure EFI hose with EFI rated fittings plus EFI clamps work well with two-rail EFI.  Double-flare steel pipe with flare nut ends is commonly sold for both fuel and brake use, brake being much higher pressure needs than fuel.  Confirm that the line you're buying is acceptable for both, as fuel can be corrosive.


Your idea about quick couplers for fuel is feasible.  Check with Summit Racing and the many racing fuel line suppliers.  You will likely find a source for high pressure EFI hose with garter spring or clip spring couplers—similar to OEM fuel grade hoses.  You would need to carry the special tool for releasing these couplers!  Don't lose the tool on a trail...


If you have access to a new OEM fuel regulator, try it.  You're running a gauge to confirm pressures in any case.  Find a permanent and safe gauge mount, and be very careful, there is gasoline under high pressure and volume running to that gauge!  Make sure the gauge is designed for ongoing use.


As for a plate at the tub floor above an in-tank fuel pump, you're right.  Stainless cannot be welded to the tub sheet metal, and you do need an anti-corrosive approach here.  Again, I would consider mounting remote (not an in-tank) pump(s) and filters at a more accessible yet protected location.  A custom steel skid plate or box enclosure might work.  You have options based upon your choice of the pump and filter location.


Make sure the filters are rated for the kind of pressure involved.  If the Mopar EFI conversion kit called for mounting the filter(s) before the pump, do so.  If designed for placement between the pump and the EFI system, do so.  There is a big difference, however.  The suction side pull will generally not damage a filter.  However, high pressure on the push side of the pump can damage a filter if not designed specifically for this usage! 


If you hit the wall on pump or filter options, the Summit Racing outlet at Sparks is nearby.  They likely sell the aftermarket fuel pump that came with the Mopar EFI kit.  If so, Summit would have recommendations about filtration and where to mount the filters.


Remote fuel pumps of this design need to be somewhat close to the fuel pickup point at the tank.  That may dictate a certain location for your pumps.  There is nothing inherently wrong with these aftermarket pumps, although the new Mopar in-tank module would provide the kind of service expected from a stock YJ Wrangler or XJ Cherokee...Since you don't need an OEM pump module for your tank fuel gauge sender, the remote mount, aftermarket pump would be that much more appealing.


I'm here to continue the dialogue, Mark...Many will benefit from your questions and solutions.





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thanks for the reply.  i want to retain the in tank pump as primary feeder and the external pump only for emergency back up.  i like the idea of perhaps a ball valve, so to switch over by climbing under and unplug/plug in and go.  The biggest issues i've had with the external mopar pumps (yes, all are the conversion model) is depriming after sitting a while or the supply line drying out and cracking, thus sucking air. that can add a lot of stress to the day. 


The only way I have found to re-prime the external pump is to use a 10' length of heavy wire with alligator clips and manually add 12 volts to the pump to force run for about 15 seconds-- this brings pressure right up.  Reliance upon key on/off will not do it.  I will pass on the YJ module  and plan is to look for a replacement pump to attach to the existing top flange, power connections, support assembly shown on the pix, etc.  Any opinion on the yj-xj in tank pump? (PN 52018391P)  Sufficient pressure and volume?


the welding will be the brown round dinner plate size piece of metal that i want to reinforce in this area when the pump mounts to top of tank.  it's just mild steel and was painted tan for an unused project.  Clean it up, have the center opened to accept the tank top flange, tap screw holes and tig into place, thereby reinforcing the mounting area.  as it is now, it is not even level--somewhat warped. Thus the cracked seal and leakage. 


Until I hit megabucks, will just use new fuel lines and work on plumbing in some hard line as necessary.  Obtain new in tank pump to fit on the existing flange and support assembly, get tank repaired and hit the trail.  Going on the jeep jamboree in late July, so every day is critical...



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Mark...Understand the priming time, the OEM pump cycle is short, expecting the fuel to flow readily.  With a new pump and filter, and a new regulator, this should be less of an issue.
As for the pump #52018391P, not sure about the "P", but this is a 1991-95 Jeep YJ Wrangler 4.0L pump that should work with your Mopar EFI conversion.  Common Walbro replacement pump pressure can be 45 PSI or so with 21 GPH flow, still adequate for your 4.6L fuel demands. 
Be careful when ordering, the typical Walbro replacement pump under this number (without the "P") is just that—a pump only.  You need the rest of the module assembly to mount the pump in the tank.  If you have the in-tank module frame from a 1991-95 Jeep YJ Wrangler, here is a link to the Jeep/Walbro replacement pump at www.fuelpumps.com:

They also list a '91-'93 4.0L Wrangler pump #4637193 that has higher output (65 psi and 24 GPH):
     Note: Each of these pumps are designed to fit the OEM pump module, they are not fitted at each end with a host nipple—one end only.  See the illustrations for details, this may not work if you don't use the OEM module stand.  Contact www.fuelpumps.com and see whether they have a universal Walbro that has hose fittings at each end and the flow rate you're looking for, Mark.  As long as the pump wiring will match the Mopar EFI kit approach (confirm before buying), that should do it.  Share the Mopar EFI kit pump number with them: 1-888-841-8288.
For Mark and others interested, I created this Mopar catalog excerpt in PDF download to illustrate the pump module design and OEM part numbers:  YJ Fuel Pump Modules.pdf
As a footnote, your photos are useful to others, Mark.  I see how you’re doing this whole thing, make sure the “dinner plate” mount has a fuel resistant seal!  Regular rubber will not work, use fuel-proof O-ring, gasket material or whatever provides a safe, permanent seal.  You do not need or want fuel leaks.  Avoid sloughing sealant into the tank, sealant can plug up the pickup sock.  Summit Racing may have some solutions here.  Let us know what works.


Consider a “Thread Sert” solution for your plate mount to tank.  Below is a PDF download on this product.  R&E Fasteners may have them locally at Sparks, may need the installation tool, inquire or look online.  Thread Sert eliminates tapping, welding, brazing or distorting the fuel tank surface. 


Thread Serts.pdf


This should all work, I can see where you’re going with it!  Get a Walbro/U.S.A. built pump for better reliability.
Selecting a Walbro pump is not rocket science.  You need a matching wire setup and fitting arrangement...With a spotlessly clean tank and a properly sealing gas cap (a must for your four-wheeling), you can run the Mopar EFI pump successfully.  The new pressure regulator will help, too.

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Moses wrote:


 Note: Each of these pumps are designed to fit the OEM pump module, they are not fitted at each end with a host nipple—one end only.  See the illustrations for details, this may not work if you don't use the OEM module stand.  Contact www.fuelpumps.com and see whether they have a universal Walbro that has hose fittings at each end and the flow rate you're looking for, Mark.  As long as the pump wiring will match the Mopar EFI kit approach (confirm before buying), that should do it.  Share the Mopar EFI kit pump number with them: 1-888-841-8288.



Not clear here Moses.  The link shows the in tank pump that has an exit tube that i will connect to the supply (going thru the top mounting flange and out to filter, etc.)  The bottom of the pump affixes to the pick up sock screen.  All I need to is attach power (using the existing blade connectors already on the pump support tower, attach pump itself to the support rod, adjust for height and go. 


I like the thread sert idea.  The hole the in tank pump was not an Areo option-- we did that after the fact, picking a suitable location and dropping a 3" bi metal hole saw to make the opening then drilled and tapped the pump mounting screw holes..  The base material is very thin and eventually impacts to the tank caused the top to warp with attendant leakage and 'I smell gas' comments.  The 'dinner plate' idea is to beef up and reinforce the super thin mounting area and better distribute to load over a larger area. If not, then thread sert 1/4" plate to uneven 1/8" tank material may not hold. By comparison, if you can see where the smaller hole accepts the sending unit.  It has a thick collar welded around the opening.  That is what i want to do with the pump opening.  My friend runs a machine shop to open the center of the plate to the exact dimension of the top flange.  If the plate is  tig (or?) welded to top of tank, only need a gasket for the 3" round opening where the flange assembly drops thru the dinner plate down into tank.  Then tap the flange mount holes into the dinner plate.  Its hard to describe with words only... argh.  Since the dinner plate is mild steel, concern is whether any undersurface exposed to fuel will cause rust...  but i guess rust is the law...paint will only come off into tank.  powder coating seems impractical.   I could skin it with a thin piece of stainless underneath...  


I will order the second of the two walbro pumps you linked and get this process going.





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Mark, I have your photos and fuel supply system in perspective, thanks...


As for TIG or welding the "dinner" plate to the top of the Aero tank for reinforcement, you're right about mild steel and corrosion around fuel.  Two options here: 1) galvanizing the tank, if possible and practical, after welding the plate in place or 2) have the radiator shop treat the tank with chemical liner for fuel. 


This coating is a common process that McCarran Radiator at Sparks has done for me on vintage, rare fuel tanks.  If you have something going with A-1, ask about coating the inside of the tank.  If done properly, this not only seals, it will prevent the corrosion and oxidative rust you have concerns about...TIG the plate in place and cut any holes before cleaning and coating the inside of the tank.


Thread Serts do have their place, and they work.  Serts would enable making a round reinforcement plate of stainless steel or other non-corrosive material.  Enough Serts would hold well around the circumference of your big round plate or a similar non-corrosive plate.  You would need to make a sealing gasket of some kind. If you believe the thin tank top would still waver, even with a circle of Thread Serts in place, quality TIG welding would eliminate any risk of buckle, seepage or a loose plate. 


Keep us posted, Mark!



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  • 2 weeks later...

Thinking of a serviceable fuel filter when I install a new Aero fuel tank.  Phenix Industries F78100-H is 100 mircon.  Is that sufficient compared with the mopar yj filter?  (cannot link to the info)  its very durable, stainless inside and is re buidlable with an internal element:



I can adapt the filter and other connections with 8AN fittings to make filter cleaning/removal a snap. Will also plumb the external pump (to be held in reserve for an emergency) with same fittings so if there is a fail, simpy unscrew the in tank line and swap over the line from the auxiliary pump! 


Auto Meter fuel pressure gauge in transit along with an adapter for the fuel rail.  remove the needle valve in the schrader on rail, screw on this Y adapter.  It retains a Schrader to bleed down system or add a tool, and the other part of the Y accepts the auto meter sending unit that then runs electrical power to the gauge in the cab.


finally, awaiting delivery of gabriel hi jacker air shocks for the rear to assist road manners when loaded up with 30 gal fuel, camp gear and towing a trailer.  Will power/deflate each independently from cab using on board air already in place.


next weekend will be the big build/wrench fest...Need to make the Rubicon Trail next month!



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Mark, I looked at the product, drilled down, there’s no mention of pressure rating.  If this will handle 80 PSI or more pressure without restricting flow, it could work.  (Your EFI fuel regulator setting is well below this figure.)  I would think 100 micron filtration could be okay as a pre-filter (before the pump) with a pickup sock and return flow to the tank. 


The idea is to prevent clogged injectors, and 100 micron is marginal.  The filter is serviceable, a plus for your kind of use.  With ready access and ease of service, you’d be a happy camper on that note. 


K&N has a series of high performance stainless fuel filters like the one you sought out.  In the K&N lineup, ratings range from 25-100 micron—100 micron for gasoline is not that exciting, and this would be used in an engine where flow rate (GPM or GPH)  is crucial.  Here are K&N's offerings:




Make sure of the pressure and flow rating (without significant pressure drop across the filter).  100 micron, by itself, would only protect injectors to a minimal degree.  The range from 25-100 micron filtration is about flow rate and maintaining pressure in the system.  OEM filters are much finer filtration than 100 micron. 


Your volume and flow must meet a 4.6L-5.0L engine's injector flow needs (24 lb/hr @ 39 PSI) after the filter.  To know your maximum (ever) fuel demand, start with the premise that each injector can flow 24 pounds of fuel per hour.  You have six injectors, so multiply 6 x 24 = 144 pounds per hour maximum flow.  If gasoline weighs 6.2 pounds per U.S. gallon, you divide 144 by 6.2 = 23.22 approximate gallons of fuel flow per hour!


So, you could get by with a filter capable of, say, 25 gallons per hour flow for maximum demand.  If the filter manufacturer provides a GPM rating, simply multiply the GPM figure times 60 to determine GPH.  If your fuel supply pressure were much above the 302 V-8 injector's 39 PSI pressure rating, you would need to add fuel demand accordingly.


Something to put into perspective: What is the maximum rate of fuel you have ever burned with a Jeep inline six under load?  Can you imagine burning fuel at the rate of 25 gallons per hour, even under hardcore 'wheeling conditions or trailering?  Flow rate reflects maximum fuel demand regardless of the time interval.  It could be just an instant, like wide open throttle acceleration in a passing situation under load.  Fuel flow rate and pressure must be on tap every millisecond of the hour!


Your 4.6L engine with the 252 camshaft and reasonable rpm ceiling could tolerate a 10-25 micron filter as long as the manufacturers' flow and pressure ratings are adequate...If absolute cleanliness at the injectors is the point, go with 10-25 micron on the post-pump side—with enough flow capacity and high enough PSI rating to handle your pump's pressure and fuel injector flow rating and demand. 


Note: Since your two-rail pump/supply pressure is regulated, with excess fuel returned to the tank, the actual line pressure is only equal to the rail regulator's PSI setting as read at the Schrader port. 


Here is a high performance website that recommends 90-micron as a "pre-filter" only—plus a 10-micron post filter.  You must have adequate flow in any case.  This outfit also offers a very nice dual pump/backup system (somewhat pricey by the time you factor filters into the package), which I discussed earlier.  Scroll to the bottom at the website page for filter information:




Trust this is helpful, Mark...



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