Fuel pump & regulator requirements

[275/350 I-6]

I have a 4.7 build that I’ll be putting together soon, it will be going in my 1985 CJ-7 auto. I have had the block machined for the pistons & rods from Russ, with a 4.2 crankshaft. I have a Comp-cams camshaft from Russ as well. I have the late model curved runner intake manifold and a 62mm throttle body, with 24 Lb injectors from Russ as well. I would have had this engine together and running by now, but my foot is in a cast, and I’m non-weight bearing for another six weeks. Since I can’t work on my CJ-7 engine swap, I’m trying to figure out the rest of the parts I need to order so I have them ready to go when I can walk again this spring.

My biggest questions are with the fuel system. My 1985 CJ-7 has a OEM 15 gallon steel fuel tank. I plan on installing a 20 gallon OEM plastic tank. I plan on installing an in tank fuel pump assembly for a 1995 YJ, in my 20 gallon OEM plastic tank. I plan on modifying the plastic tank by cutting a hole shaped for the fuel pump assembly designed for a 1995 YJ, and it will be centered so the pickup is in the sump, in the center of the tank. The OEM 20 gallon tank fuel pickup/sender unit is off to the right side. I plan on using an OEM pickup sender unit with my OEM fuel gauge in my OEM speedometer. So, I’ll have one sender in the round hole on the right side for my fuel gauge. And the rectangular shaped OEM YJ pickup sender mounted in the center delivering fuel to my fuel rail.

I understand there are two different style fuel rails for these engines. A dead head and a return style regulator are used depending on the year. I believe I have the early style fuel rail for the 1996 and down OBDI (fuel rail and engine harness). I believe my fuel rail is the dead head style. I am not sure which style I want, and this is where I need some help. I don’t have any experience with these 4.0 engines other than what I have learned from Russ, this website and other sites on the web. So, if anyone can provide some insight on what I need to make this little 4.7 inline six run well,I would appreciate any input and suggestions.

I’m going to attach a picture of what my OEM 20 gallon plastic gas tank will look like with the YJ pump mounted. I will use the OEM sending unit in the round hole, because it is compatible with my gas gauge in my speedometer.

[Cheromaniac]

It would be easiest for you to use the return style injector rail, 39psi regulator, supply/return fuel lines, fuel filter, and fuel pump assembly from a '91-'95 YJ.

[275/350 I-6]

OK. So what you are saying is to use the entire 91-95 fuel system (OBD-I). Are these regulators adjustable? It seems like having a pressure adjustment feature would help with tuning. Thanks.

[Cheromaniac]

Unfortunately the stock '91-'95 fuel pressure regulator isn't adjustable, and Hesco's adjustable unit costs $179.

https://hesco.us/products/7973/fuel-pum ... j0SYTEza00

[Cummins90]

Or you could take a 1996+ returnless rail and have a return port welded in? Or remove the shrader valve and use the pressure diagnostic port as your return. Lots of options.

What engine control system are you using?

[275/350 I-6]

I have a ECM & harness from a 1995 Cherokee manual transmission. I’ll be using the TF-999 that came in my 1985 CJ-7.

If I used a 1996 and up, fuel rail with a return fitting welded on, how would this differ from the 1995 and down, return style fuel rail? Like I said, theses engines are new to me, so I need as much info as possible, until I figure out what is out there and what works good for a well built 4.7. Thanks!

[275/350 I-6]

Unfortunately the stock '91-'95 fuel pressure regulator isn't adjustable, and Hesco's adjustable unit costs $179.

https://hesco.us/products/7973/fuel-pum ... j0SYTEza00

That sounds like it might be a good way to go. I could start out with the fixed pressure regulator (39 PSI), and if I need for fuel pressure the Hesco regulator might be a good option. Thanks.

[Cummins90]

It just matters how you want to run the regulator. If you get a 96+ you can have any fitting you want installed and run any regulator. It would also be easier to adjust as I assume the hesco cannot be adjusted on the rail?

You will be running a wideband right?

[275/350 I-6]

It just matters how you want to run the regulator. If you get a 96+ you can have any fitting you want installed and run any regulator. It would also be easier to adjust as I assume the hesco cannot be adjusted on the rail?

You will be running a wideband right?

When you say “any regulator” it sounds easy, but I am not real familiar with these engines, do you have any specific regulators in mind, or suggestions?

I’ll run a wideband and if I need to? So far you are the first to bring it up.

[SkylinesSuck]

Fuel pressure regulators are mostly all the same (raising rate vs static aside) just the fittings are different. You can adapt anything to your current rail.

A wideband O2 sensor tells you your air/fuel ratio. Not having one is just a wild shot in the he dark unless it's a known setup and even then, you would only be in the ballpark. Get one.

[SkylinesSuck]

Not recommending this one per se, just an example:

https://www.summitracing.com/parts/tnk- ... PAQAvD_BwE

You would need fitting and lines to adapt it to whatever you have.

[275/350 I-6]

Fuel pressure regulators are mostly all the same (raising rate vs static aside) just the fittings are different. You can adapt anything to your current rail.

A wideband O2 sensor tells you your air/fuel ratio. Not having one is just a wild shot in the he dark unless it's a known setup and even then, you would only be in the ballpark. Get one.

Ok, got it. Any aftermarket pressure regulator for the pressure range I’ll be working with can be adapted. I wasn’t sure if there was another OEM style regulator to use maybe? Thanks for clearing that up.

Now I need to research wide bands, do you recommend any one in particular?

I’ve been tuning without one for years, but you’re right. If I want to get the tune right, it’s time to step up.

[275/350 I-6]

Thanks to everyone that has replied. I understand the fuel system better now, and I have a plan to move forward with this engine build. I can’t wait to get this cast off my foot and start walking again. I’ve been out to my shop twice since my surgery on New Year’s Eve to check my freshly machined engine parts, I don’t want anything to rust. I can’t wait to walk normally again, and get back to work on my Jeep.

My plans are to run the early fuel rail with the fixed pressure regulator initially and see how it runs, and go from there. If I need to chase the tune, that’s what I’ll do. Whether I use the Hesco adjustable regulator or modify a fuel rail with a aftermarket regulator, I’m not sure which way I will go, but either way should work.

As far as the wide-band goes,It looks like I can get an auto meter guage for around $200, but I’d rather get a setup to do the tuning, and then remove it after the tune is good. I don’t want another guage in the dash, so I’ll keep looking for something I can buy to tune with, that is a not permanent part of the vehicle. This way I can use it on other vehicles.

My Jeep will be getting a new exhaust system for my new engine. I will have an extra bung installed for the air fuel sensor, and then plug it after the tuning is complete.

[275/350 I-6]

My pan is to try to modify a 1997 and up fuel rail to have an aftermarket fuel regulator, guage, and a return fitting. If it doesn’t work out, I can purchase something aftermarket like this one. It has an AN plug in each end, so I could make it work. Does anyone have a picture of their setup? It would be nice to see how it is laid out in/on the engine. Thanks again for all the help.

[SkylinesSuck]

I've never seen that rail before! Cool! Probably going up order one just because