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1988 Jeep 2.5L Comanche Won't Start!


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Hello, I'm new here from Montreal, Canada

 

While heading out on vacation, my Comanche's alternator pulley came loose and the serpentine belt came off. (the pulley was put on a RB alternator by a impact gun)

 

I was dead on the road but remembered a Canadian Tire was a short distance away so I removed the belt and drove to it. I removed the alternator and had it tightened. (same way) I reinstalled the belt and tightened up the power steering adj. for the belt.

 

Then, the Comanche would not Start. I got towed back home. Besides not starting, the fuel guage was pointing to the Floor which looked like the Crank position Sensor but that was OK. I got Spark but no Fuel. There is no voltage to the pump. Fuses check Ok, the fuse box is Ok, no corrosion.

 

Thanks For any Info  :wacko:

 

Steve

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Hi, Steve, welcome to the forums!  Did you check the fuel pump relay?  The alternator voltage spikes could impact the ECU (the worst case, so save that possibility for last) or the relays.  Grounds from battery to body and engine can be troublesome on the earlier XJ/MJ and the YJ Wranglers.  Check grounds for continuity and integrity.

 

Below is the wiring schematic and circuits for a 2.5L TBI fuel pump (similar YJ Wrangler application).  Note what triggers and powers up the pump.  If necessary, try to activate/test the pump by isolating it and using jumper leads:

 

Jeep YJ 2.5L TBI Fuel Pump Wiring Diagram.pdf

(Schematic #9 is at the end of the PDF.)

 

Worth reading is this very recent exchange at the YJ Jeep Wrangler forum:  http://forums.4wdmechanix.com/topic/596-1989-jeep-yj-wrangler-25l-tbi-vapor-lock/.  There are some pump related tips in that discussion.  There are a variety of other 2.5L TBI exchanges here at the forums.

 

Here's a popular Jeep 2.5L TBI troubleshooting article at the magazine:  http://www.4wdmechanix.com/Tuning-and-Troubleshooting-the-2.5L-Jeep-TBI-Four.html.

 

Keep us posted on your progress, glad to continue the discussion and provide more tips and information if needed...

 

Moses

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WolverineCub...Ah, this may be simpler.  Maybe a fusible link issue.  The Comanche has a 14-gauge and two 18-gauge fusible links that feed to main power.  Identify the fusible links, they're in the parts listings as J8134201 (18 gauge, there are two) and J8133785 for the 14 gauge.  In parts illustrations, they appear to be ring eye wires attached at the starter solenoid and possibly the direct lead from the alternator.

 

When there is a "global" electrical issue, the battery, ignition switch, main cables and fusible links become suspect.  Also, don't count out a battery problem, the short could have knocked out a battery cell.  Test the battery under load, it may have an open...Attempt the simplest checks and fixes first, like checking the battery for an open or the fusible links for continuity.  Check the lead from the alternator, you know it took a hit.

 

Moses 

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Voltage test is convincingly low if that's with the engine not running.  Engine running, you should get alternator voltage readings, well over 12.9V.

 

Remove the battery and get it load tested.  Most can get this done for free.  In the U.S., AutoZone or NAPA will load test a battery without cost.  If the battery is damaged or has open cells, you've found the problem.  The fuel pump should have 12.3V minimum to run.  Your engine/starter is not cranking over with this kind of voltage, right?

 

Moses

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Terrific, Steve!  Proves the point:  On a D.C. system, the ground integrity is as important as the positive leads.  This is a  time-honored concern, as voltage drop caused by poor grounds can dim lamps and raise havoc wherever a device requires 12VDC.  Test ground circuit resistance and for voltage loss if you can get your hands on a Fluke 1587 or equivalent meter...Test grounds as you would the "hot leads".  Isolate this ground to chassis issue. 

 

In my books and articles, I have emphasized the importance of quality grounds on a D.C. system.  When installing an onboard welder with a very high output alternator, for example, I share that all positive and ground cables should be 1/0 welding cable with high grade crimping or soldered terminal ends.  The reason is that their is no integrity in a 12VDC electrical system if either the ground or hot side has too much resistance.

 

There must be a relationship between the alternator fiasco and this ground failure...Please let us know what you find and how you resolve the problem.  Look for oxidation and corrosion at the ground terminal ends and for corrosion wicking up the battery cables and other ground cables.  The XJ Cherokee and MJ Comanche have unitized body/frames that should provide good grounds.

 

Moses  

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