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  #1  
Old June 8th, 2015, 14:04
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Converting the 4.0L OBD2 fuel system to a return style system?

I was curious if anyone here has done this, and if so what parts you used? I'm also curious if there is an aftermarket fuel rail out there?

TIA!

Bryson
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Old June 8th, 2015, 14:09
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

Would the Renix fuel rail fit?
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Old June 8th, 2015, 14:24
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

I cant find an aftermarket fuel rail for the 4.0. This guy has a FPR mounted at the rail with a couple of OEM looking snap fittings. Its technically the same as an OEM setup because the FPR is before the actual rail rather than having the FPR regulate after the fuel in.

http://www.jeepstrokers.com/forum/vi...php?f=5&t=4348

Is there a reason why you want to do this? Are you loosing fuel pressure at the rail when in high boost and just want the fuel pressure to be high hitting the rail and regulated after the injectors?
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Old June 8th, 2015, 14:30
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

My bet would be that with all that turbo heat, you could get vapor lock even at the higher pressure. The circulating system always brings cooler fuel from the tank and sends the hot fuel back to the tank.
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Old June 8th, 2015, 14:33
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

91-95 uses a return on the rail
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Old June 8th, 2015, 15:03
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

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Originally Posted by old_man View Post
My bet would be that with all that turbo heat, you could get vapor lock even at the higher pressure. The circulating system always brings cooler fuel from the tank and sends the hot fuel back to the tank.
Pretty much dead on. I haven't had vapor lock to the point where I get a no start, but if I let it sit for a while it definitely isn't happy firing back up.

I'm looking at reworking the fuel system this summer to include an inline filter and a bigger pump. I don't really want to upgrade the pump without going to a return style system.

Quote:
91-95 uses a return on the rail
Will it fit the late model intake manifold/EV6 injectors though?
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Old June 8th, 2015, 15:16
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

Quote:

Will it fit the late model intake manifold/EV6 injectors though?
It looks like the OBD1 rail will fit actually. This may be the route that I end up taking.

Now what about the fuel tank side?
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Old June 8th, 2015, 15:19
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

IIRC, you should be able to just swap the assembly into the newer tank. An older model tank shouldn't be that hard to source if needed.
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Old June 8th, 2015, 15:42
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

The older models had the assembly through the side, his 99 has it through the top. You might be able to swap tanks, thats the only way the older style is working

You might be able to just stick a straw through the assembly with a check valve on the line
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Old June 8th, 2015, 15:44
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

Seems like the assembly should not just swap over since it is horizontal vs vertical. Replacing with a 91-95 tank would do it though. Alternatively you could just tap the tank for the return. If youre upgrading to a bigger pump, consider running a new line for the feed and then reusing the existing feed line for the return. You would still have to swap taps at the tank but at least you have a good 5/16" hard return line.
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Old June 8th, 2015, 15:56
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

Can you physically hang an early model tank off a late model?

I would consider fuel flow when you're figuring this out. It shouldn't be tough to build a new fuel rail if you find that the OEM chokes it up too much.
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Old June 9th, 2015, 07:21
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

There is this: https://www.novak-adapt.com/catalog/...uel_module.htm a bit $$$ but you get some ideas. I thought someone made another kit to just convert the pump housing, but I can't find it at the moment.

Edit: http://stores.hi-potek.com/fuel-pump...ceted_search=0
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Old June 9th, 2015, 14:26
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

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Thanks for posting that. I might use those for my LS swap!
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Old June 9th, 2015, 17:49
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

wow wonder what the margin is on that adapter, 400%? Would definitely be a convenient piece and a lot more tempting at $50.
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Old June 10th, 2015, 12:58
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Re: Converting the 4.0L OBD2 fuel system to a return style system?

The return less system doesn't really circulate the fuel in the rail. The rail is still pressurized like the return less system and all the extra fuel just goes back at the front of the rail. It doesn't go all the way through the rail. Both the input and return are at the front of the rail so there is still hot fuel in the rail until it gets used.

The only advantage I see is if the fuel lines themselves are what is heating the fuel.

The other thought is to braze the feed to the rear of the rail and use the stock return at the front of the rail. That is the only was you would get the fuel to circulate the rail.
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