94 YJ 2.5 to 4.0 swap Problem {nightmare}...

    How do I start this horror story... Short and sweet... Here is my problem...
    Fuel injectors are not firing... Wow... Sounds simple... Maybe it is and I am a moron... :question:
    Long part...
    Swapped a tired 2.5L with 168,500 on the clock... AX5 that has not had 5th gear for 3 years...
    Put in a 1994 4.0L out of a 94 YJ with 62,000 on the clock, and an AX15 with new syncros...
    Plug and Play... You would think...
    Also changed my input to my transfer case to a 23 spline..
    Mounts ground off and re-positioned. Everything is back on the vehicle...
    Lets see... Parts... Complete tune up, fuel filter, all new diff fluids, fresh GL in the trans, New 3 row rad for the 4.0, new hoses, belt, clamps.. New centerforce stage I clutch, pilot bear and bush, throwout bear and fly wheel...... New starter... And a fresh Mopar Oil Filter and 6 quarts of Valvoline...
    Will run if I dump fuel down the throttle body throat, but can not get the injectors to fire...
    Things I tried, New Coil, New Cam Pick-up, in the distrib., New CPS...{and made sure it energizes everything, pull off the flywheel, 2 x's, then down to the flywheel, you hear the relays and fuel pump energize} New fuel pump and strainer... Longer fuel lines... All new fuel line plastic lock clips... Checked all fuses... Even threw a new alternator on the pig... I have lots of spares now... New fuel pump relay and the ASD relay... Fuel pressure regulator on the fuel rail also new... Fuel pressure is good, and I have good vaccum... No codes, {on, off, on, off, on} Get an 11, 12 and a 55.. Yes, I disconnect the battery when working on the heap... I am sure I missed a part or 2 that I have replaced... But that is all I can think of right now... :doh:
    OH, almost forgot... Had the ECU cleaned and tested by A-1 Cardone... All OEM Specs met... But I am still not getting a signal to fire the injectors... I tested 2 of them, 12 volt open / close click test and seemed to work.. When I crank the heap I just get a solid light on them... Always under power, not shorting to ground...
    Now, my suspicion... The 2.5 had a power steering pressure switch on the pump. And it appears to be tied into the fuel system... I would think the 4.0L ECU would not be aware of this, but also, might the harness in the YJ that had the 2.5L be wired slightly different from the 4.0L without a Power Steering Pressure Switch? It appears to possibly be the problem or possibly a cause for circuit failure... Also, my other thought was that a fusible link went bad somewhere in the chassis...
    Wheeewww... My fingers hurt now from typing all this...
    I am sure I forgot a thing or 2 here... :shrug:
    Thoughts/ Inputs appreciated!!! I am going bald and contemplating making it a big flower pot on 36's...
    :repuke:

    well if you decide to make a flower pot.. let me know cause I will run over and put some old 33's on it so i can have your 36's.. :yevil:
    and this would also make it easier to get the dirt in.. it would be 3" lower......

    Distrubutor 180 out? 2.5 harness may have different resistance than 4.0 harness when it comes to sensors? Solid stream of fuel from fuel rail? Bad ground? Not a good switched 12v source ? Just some ideas.



    Bryan

    Quote from "B2hi"

    Distrubutor 180 out? 2.5 harness may have different resistance than 4.0 harness when it comes to sensors? Solid stream of fuel from fuel rail? Bad ground? Not a good switched 12v source ? Just some ideas.



    Bryan


    Runs really good with fuel dumped down the throttle body. Harness resistance, no clue. But I thought they were pretty much the same... Going to check my fuel return line... Somebody suggested it may be blocked :question: 35 PSI on the fuel pressure.. The rail has fuel in it, but does not seem to have pressure??

    OK
    first things first



    I did this swap last spring


    The switch on the power steering punp is not used on the 4.0
    this systen bumps up the idle if the PS pump is under high pressure
    like when the steering is turned hard to one side.


    Sounds like a crossed wire


    Pull the ECU plug and test the wires going to the fuel injectors.
    Pin by Pin

    Yes, ecu came with the engine and trans. Also had the ecu checked out at Cardone in Philly... The steering sensor wiring in the 2.5 is tied to the FI... I know it is not in the 4.0, but I am thinking it is causing the problem because of an in-complete circuit?? Also, the YJ it was pulled from did NOT have a security system... So the ECU should not be locked because of that... :question: Everything works but no injector firing... Jeep runs good with gas in the TB, but for some reason, cannot get the injectors to feed... :question:


    did you get the 4.0 wire harness with it also?



    Sounds like a crossed wire


    Pull the ECU plug and test the wires going to the fuel injectors.
    Pin by Pin

    Yes, harness, motor, ecu and trans all together... I think I may have found the problem... Brown / Red wire and a blue and yellow have no home, they have crimp lugs on them. If I find out where they belong, I think the problem will be solved... :question:

    I hope you have a FSM
    it helped me greatly.


    I had to almost rewire the ehtire harness adding the
    auto tranny lines.


    A bad crimp can be your problem but I do not think the power steering
    switch is a issue.

    Power steering switch is only their to signal the ecu to "bump up the idle" in the case of stationary turning or increased load turning. It should not affect whether the injectors fire or not.
    If your injectors are "hot" all the time then you have a wiring problem, but you know that already. I know ford injectors only fire when grounded Something is backwards in your "hot start only" wire,"hot run/start wire". The injector stays hot and only fires when the computer tells it to ground and thus fire. Of course this is the way the Ford system operates, I am only assuming the jeep system is similar.

    Quote from "Hasselholf"

    Power steering switch is only their to signal the ecu to "bump up the idle" in the case of stationary turning or increased load turning. It should not affect whether the injectors fire or not.
    If your injectors are "hot" all the time then you have a wiring problem, but you know that already. I know ford injectors only fire when grounded Something is backwards in your "hot start only" wire,"hot run/start wire". The injector stays hot and only fires when the computer tells it to ground and thus fire. Of course this is the way the Ford system operates, I am only assuming the jeep system is similar.


    That is what I am trying to figure out. It is not grounding. Hot all the time. So there may be a wire switched in the 2.5 to the 4.0 harness? I was hoping or figured somebody else already had this problem... Like I said, dump fuel down the throttle body, runs like a top.....

    FIXED... Fuel lines swapped under the drivers door... :shrug: Both are the same size, not like on the fuel rail... Go figure... New jeep runs awesome... :rollsmile:



    Quote from "Dmger"

    FIXED... Fuel lines swapped under the drivers door... :shrug: Both are the same size, not like on the fuel rail... Go figure... New jeep runs awesome... :rollsmile:


    Awesome!
    Funny when it is somthing small like an Oops I swapped the fuel lines.


    I'm glad it is running! You will love the added power :up:

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