1986 XJ Cherokee 2.5L TBI Not Firing

[Chris Caronna]

So I replaced the head assembly, rods, lifters, cam, timing chain, etc. Everything except the pistons basically. I took it to a mechanic at first but after taking it apart e decided he didn't want to work on it. I've put it back together without any left over parts. I know the cam timing is ok, I lined up the dots on the sprockets (see photo). When I dropped in the distributor I had the oil pump notch just past the 3 o'clock position, and when it dropped in the rotor was at the 6 o'clock position just like the manual says. But to make things even better, when the engine is turning over, every once in awhile a puff of fuel will shoot out of the injector. I replaced the injector, same thing. The only thing I am not sure of being the same as before the work started is 1 orange wire (see photo). It goes to the connector (see photo) but I haven't followed it back any further. Anyone know what it is supposed to be connected to?  Is there a wire that is supposed to be screwed to the distributor case? I replaced the distributor because the casing was cracked on the old one.

[Moses Ludel]

Hi, Chris...What year is this engine?  2.5L TBI or MPI?  I'm guessing this is a pre-1991 TBI engine?

If a TBI 2.5L model, the orange lead is the KEY ON/Run feed to many devices on the chassis, the ignition module, fuel pump and ECU.  Orange runs in 14, 18 and 20 gauge wires depending upon the voltage demand of the device(s).  On 2.5L TBI models, the orange leads to the ECU are connections/pins #27 and #35.  #27 goes to the ignition module.  #35 goes to the heated oxygen sensor. 

Orange also feeds one side of the TBI fuel injector (hot KEY ON side) while the other injector lead should be light blue on a 2.5L TBI engine.  See whether the orange lead is hot with the key on.  The light blue lead goes to ECU pin #21.  The ECU completes the ground at this pin.

I would check the KEY ON and ground connections, especially the ignition module and injector feeds.  The ground from the engine (near the dipstick) to the body is crucial.  A poor ground could be causing a voltage drop or faulting.  Also, I would rotate the crankshaft (KEY OFF, coil lead removed at distributor cap) until #1 piston just reaches TDC on its compression stroke  (timing mark reference on pulley/timing cover).  Verify whether the ignition rotor points to #1 spark plug lead on the cap.  Make sure the rotor points to #1 spark lead when #1 piston is at TDC on its compression stroke...Verify the firing order in relationship to the direction that the rotor turns (clockwise 1-3-4-2).  #1 cylinder is at the front of the engine, #4 at the back.

Note: The distributor shaft rotates at 1/2 the speed of the crankshaft.  When you rotate the crankshaft one full turn, the rotor moves 180-degrees.  Two turns of the crankshaft rotates the rotor one full turn (360-degrees).  When you bring #1 piston to TDC, come up slowly to avoid passing the TDC mark.  If you do pass the mark, rotate the crankshaft backward 90-degrees and bring the piston up again.  This also applies when you're verifying TDC for valve timing, as there is slack at the backside of the chain:  If you pass the TDC mark and only move the crankshaft backward slightly, you will remove the slack in the chain but will not position the camshaft or distributor.

Moses