Engine 1995 Mustang (1999 V-6 engine)--No spark after head gasket change

Discussion in 'SN95 V6 Mustang Tech' started by Venster, Dec 17, 2012.


  1. Venster

    Venster New Member

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    Hello. I just changed the head gaskets on the '99 3.8L engine in my '95 Mustang. Now it will crank but not start. I drove the car to its present location last week before I tore the engine down.

    The details:

    1. There is no spark between the ignition coil and the coil end of the spark plug that I tested.

    2. My test light shows no power to the positive terminal on the large ignition coil connector. (There IS power to the primary (small) connector.)

    3. When I tested the negative terminals on the ignition coil connector while cranking the engine, the test light flashed repeatedly on each one, indicating a pulse signal from the PCM. The light flashed very weakly each time.

    4. I also tested the crankshaft position sensor connector. NO POWER to that connector, either.

    5. I also tested the camshaft position sensor. It has power.

    6. There IS power to the fuse that I *think* governs the ignition coils--slot 18, 20A fuse, in the instrument panel fuse box.

    Any ideas? Thanks for reading.
  2. Venster

    Venster New Member

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    Correction: In detail #1 above, I checked the plug WIRE, not the plug itself.
  3. kramer

    kramer Member

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    most likely something to do with the crankshaft position sensor, but i dont know what , cause i dont see how the plugs would know when to fire without that working, make sure the coil is grounded , i cant really understand most of what your saying , but if your saying what i think you are , then if their is power and a signal going to the coil , then the problem is after the coil , and if my memory serves me right theirs three prongs on that connector that go in the coil one should be the power , ones the ground , and i think one sends a signal , not really sure how all that works , im only 19 lol , but you should get power from the signal prong as well as the power prong , if not the problems before the coil ,i think lol , but im pretty sure the coil and the crankshaft position sensor work very closely together , are you getting any kind of readings at all from it?
  4. kramer

    kramer Member

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    heres what my haynes manual says about the crankshaft timing sensor ,

    the crankshaft sensor monitors the pulse wheel as the teeth pass under the magnetic field created by the sensor , the pulse wheel has 35 teeth and a spot where one tooth is missing . by monitoring the last tooth , the sensor determines the piston travel , crankshaft position and speed information and sends it to the PCM

    and heres how you check it


    1 . disconnect the crankshaft position sensor electrical connector and with the ignition key on (engine not running) check for battery voltage to the crankshaft position sensor

    2. install a voltmeter into the crankshaft position sensor and using the AC scale , check the voltage pulses as the gear is slowly rotated . use a large breaker bar and socket to rotate the crankshaft pulley

    3. if no pulsing voltage signal is produced , replace the crankshaft sensor
  5. Venster

    Venster New Member

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    Thanks for the info. The Haynes manual is the one I'm using, too.

    The problem is that I'm not getting power to either the ignition coil or the crankshaft position sensor. The manual doesn't say what to do if this happens, so I've been trying to chase down shorted wires or disconnected plugs with no success.

    All the fuses in both boxes are good. Do you know if there are any fuses not in those two places?

    Thanks again.
  6. kramer

    kramer Member

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    not really , but if their are they would be in the engine fuse box , just check them all , if none are bad , than eliminate it being that and move on , cause from my experience , if theirs a bad fuse, then its usually pretty straight forward , although you might want to look up a fuse box diagram for the engine fuse box , and take a test light to it , just poke the side of the fuse thats coming in at the right moment depending on what fuse it is and if one of them is dead when it should be hot follow it , i know thats not a whole lot of help , but i can really only help you figure it out , theres no way im gonna be able to figure it out for you , it just doesnt happen
  7. Venster

    Venster New Member

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    LOL, true. :)
  8. kramer

    kramer Member

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    im pretty sure that if you have a short with one of the main engine components than it will either blow a fuse or fry the pcm , i know its a son of a **** getting to the pcm sometimes , but if you really think its a short , id take a look , and also i guess i forgot to mention that you can just take the crankshaft position sensor out and with it probed somehow , pass small metal object like a spoon handle or something of that width infront or it and see if it creates a pulse , you can do this because t disrupts the magnetic field , also the test is in the Haynes manual, and it just says to replace it if their is no voltage reading , which leads me to believe that their is only a voltage reading when the magnetic feild is disrupted , which would make your findings of the crankshaft position sensor to be dead normal since nothing is disrupting it when you tested it , or was their? you also might pull apart some wiring harnesses and see if you didnt bend a prong or something putting them back together
  9. Venster

    Venster New Member

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    Success!

    Since there was power to the small plug/connector just before the ignition coil pack in the circuit (and I presume this small connector to be the "right radio frequency interference capacitor), I traced the malfunction to the coil connector itself.

    The power wire had come loose inside the connector. All I had to do was push it in about 1/4-inch and it had power.
  10. kramer

    kramer Member

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    awesome dude !! glad u fixed it , i knew it was some mundane detail , i think ive actually done that before , but i caught it soon after , what led you to try figure that out?

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