Question about 1989 Jeep Comanche

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89 Jeep Comanche Fuel Pump. Won't start after running great.

I have an 89 Jeep Comanche, 6 cyl. 5 speed.  The mechanic said the fuel pump was going out because it was hesitating really bad when you stepped on the accelerator.  I replaced the fuel pump and it ran great for one day.  The next morning I went to start it and it just cranked and cranked but wouldn't start.  I took the fuel pump out and replaced it again.  (The old pump worked fine at the auto parts store when the manager hooked it up to a battery).  Again, it started right up and ran great for a day.  The next morning it wouldn't start.  I am wondering if it is something electrical.  Any ideas?

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  • hpiatt Jun 18, 2009

    I replaced the crankshaft position sensor and it did not fix the problem. There is not any fuel getting to the injectors. I sprayed carb fluid in the throttle body and it fires right up. I also unhooked the fuel line prior to the fuel filter and cranked it. No fuel came out of the line. Also, there is not any noise coming from the fuel pump when you turn the key. Any other ideas?

  • hpiatt Jun 19, 2009

    I replaced the two relays that are suppose to work with the fuel pump. The problem stays the same. Still starts with carb fluid but no fuel to injectors. Is there a way to provide an external power source to the fuel pump to ensure that it is still functional? Would a volt meter help trace the problem? This is getting perplexing!

  • hpiatt Jun 19, 2009

    Thanks for your help! My email is

  • hpiatt Jun 19, 2009

    I traced the orange wire with the black tracer to the starter relay and found the wire burned in half with the plastic covering melted. I reconnected the wire and tried starting it. The wire got hot and began to smoke. Would this be a starter relay problem?

  • hpiatt Jun 19, 2009

    I have a little over 5 volts getting to C305 but I still don't hear the pump come on. Could the burned orange wire with black tracer have caused the pump to burn up? I am about to pull the pump out again and check to see if it spins.

  • hpiatt Jun 20, 2009

    I took your advice and followed the wire. I had 5 volts at the lead wire going into the tank but no response from the pump. I pulled the pump again and noticed one of the wires attached to the pump was also touching the bracket that holds the pump. I reassembled it and fixed the orange/black wire and the Jeep started! I just hope it starts tomorrow :-)

    You have been a life saver! I very much appreciate you taking time to help me and your knowledge of the situation was incredible! Thanks a million!



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Replace the crankshaft position sensor

Posted on Jun 17, 2009

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  • chryslerguy Jun 18, 2009

    possible fuel pump relay

  • chryslerguy Jun 19, 2009

    When the engine is cranking, the fuel pump is supplied by the starter relay. After it starts it is supplied by the fuel pump relay through the ballast resistor. With a test light or voltmeter check the orange with black tracer wire of the starter relay while cranking. You should have 12 volts. If the engine cranks but you don't have the 12 volts at the orn/blk wire relace the starter relay. If you have a junk email address I can send you a copy of my wiring diagram so you'll see what I am talking about.

  • chryslerguy Jun 19, 2009

    It maybe grounded somewhere along the way to the pump. I'll send the diagrams with connector views to help trace the short. If you have a volt/ohm meter you can test the wire for continuity to ground while disconnecting connections along the way.

  • chryslerguy Jun 20, 2009

    Glad to be of help, happy motoring


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On mine the fuel pump power wire retainer (the plastic piece holding it to truck)broke. wire touched driveshaft fuel pump did what you were saying at first. then shorted the lead to fuel pump inside the fuel tank. pump didn't work at all after that.shorted to fuel pump mounting frame. has done it 3 times no fire yet .just freaks me out a wire melting inside the gas tank.(the lowest gauge wire in the circuit) what i'm saying is the power wire to the fuel pump could be damaged on what the fuel pump is mounted to(the wire outside the tank)

Posted on Nov 10, 2014


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