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Renix & OBDI Fuel Delivery Differences

Old 03-07-2015, 10:02 AM
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Default Renix & OBDI Fuel Delivery Differences

I'm converting an '86 2.5L to MPI. I wanted to keep the old-school dash and front clip, so I didn't make the leap to the 97+ style and OBDII... maybe down the road. I plan to tinker with this truck for a while.


Anyway, I've gotten a remanufactured crate motor in there with a rebuilt ax5 all connected together with a '94 YJ harness. I've come to the point where I need to update the fuel delivery, and I would think the single injector in the Renix TB would require far less fuel pressure than the four in the new fuel rail.


Does anyone know the fuel pressure of the 2.5L Renix era XJ/MJ versus that of the OBDI for the same four banger?
Anyone know of a conversion method for this? I've heard I'll need to change from a side-mount pump on the tank to a top mount. Fuel line should work to make the new connections at the fuel rail, right?

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Old 03-20-2015, 10:38 AM
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FWIW, I found that both Renix and OBDI from '87 to '95 use 38-42 PSI at the fuel rail. The connections are also different- you'll need a 3/8" and 5/15" quick disconnects (I used Dorman brand). Depending on the length of your Renix fuel lines, you may need to extend them so pick up some 5/16" barbed unions, some fuel line, and fuel line clamps (not regular hose clamps).
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Old 03-20-2015, 10:51 PM
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TBI uses about 16 PSI.
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Old 03-24-2015, 10:41 AM
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Hmm... I'm getting 40psi when the fuel pump is on and its the same one supplying the 1986 TBI injector.

That's another concern I have- when the ignition goes hot the fuel pump keeps running. It's supposed to turn off after 2-3 seconds, isn't it?


I'm matching a 1993 yj 2.5L automatic engine harness and PCM so I'm finding a lot of mis-matched wires.
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Old 03-24-2015, 03:32 PM
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Originally Posted by alpine.adrenaline View Post
Hmm... I'm getting 40psi when the fuel pump is on and its the same one supplying the 1986 TBI injector.

That's another concern I have- when the ignition goes hot the fuel pump keeps running. It's supposed to turn off after 2-3 seconds, isn't it?


I'm matching a 1993 yj 2.5L automatic engine harness and PCM so I'm finding a lot of mis-matched wires.
Way too much fuel pressure for tBI.
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