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!