hoo hummm. another no start car

Electrical and Ignition

  1. demoman3955

    demoman3955 Well-Known Member

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    I guess to start with, im looking to find the best way to bi pass the ignition switch, such as which jumper wire to where. Now the back story. I use my 73 valiant with a slant as a daily driver, and its never ran perfect with carb issues and other little problems, but one day the oil sending unit wire shorted out and almost toasted other wires in the harness before i got it dealt with. it still ran like normal for a month then started running worse, and seemed like carb to me. one day went to the bank and when i went to start it, wouldnt start back up. Ive done many of the normal no start tests like air, fuel, water and its not getting spark. did the normal ballast resister, coil, ICU (which were all replaced) and a few other voltage tests and no luck. Thought it may be the reluctor in the distributor too so put in a new distributor. I did find positive voltage on both sides of the coil and im not sure which direction to look other then ignition switch at this point. Any thoughts?
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    LOL OK let's slow down LOL

    1....Shorting the oil sender wire to ground should do nothing insofar as burning up wiring. All it will do is turn on the oil light or peg the gauge if used. Of course it can ruin the gauge

    2...I assume? Your ignition is stock factory breakerless? Look at the 4 pin resistor. One end has both terminals jumpered across. That is the "key" end. You can jumper into that and still keep the resistor in the circuit, for a "quick test" jumper right to coil +. I would not run it too long on coil+ as the resistor is out of circuit

    3...Finding positive voltage at coil: With a "normal" operational system, and key "in run" / engine stopped you should see maybe 8 ish volts at coil+ this is because coil is fed through the resistor and should be drawing current through the ignition box. Coil NEG should be quite low, 1 or 2 volts

    If both sides of the coil are quite high, about same as battery, the coil is not drawing current. Either the box is not grounded, or you have a harness/ connector problem, or the BOX IS NOT GROUNDED. Remove box, scrape around mounting holes, and remount.

    you can check for sure if box is ungrounded by getting power to igntiion system, as I said above, either key on, or jumpered to ballast, or jumpered to coil+. Then stab one meter probe into battery NEG post, and stab remaining proble into ECU box mounting flange. If coil NEG is high, same as battery, and if box mounting flange shows much/ any voltage, box is not grounded. If it shows zero, either ECU harness / connector has a problem or the box is bad
     
  3. cudamark

    cudamark FABO Gold Member FABO Gold Member

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    You may also want to check the distributor drive gear. They're plastic and it's common for them to break. Just pop off the distributor cap, ground the distributor end of the coil wire, and turn the engine over to see if it also turns. You can also just try turning the rotor by hand too, but, don't crank on it too hard! If you can spin the rotor by hand, or, it doesn't turn when you crank the engine, you have a broken gear.
     
  4. demoman3955

    demoman3955 Well-Known Member

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    I put in a new distributor, tried 2 resistors, and 2 ICM. I have 3 a bodies and have a lot of parts to check with.,.lol
     
  5. demoman3955

    demoman3955 Well-Known Member

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    yeah ill start checking wires and ground again. i was thinking that it was the distributor because there is power to the coil, but its not triggering anything to spark. Im now thinking a wire could be fried at the harness inside the plug on the firewall.
     
  6. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Don't out-think yourself. You need to be precise

    1...The box replaces the points and switches the coil NEG on/ off. When the key is "in run" the box should cause the coil to draw current. What you posted earlier suggests it is NOT. Re-read my post on how to check that. Checking the NEG side of the coil, if it is "near battery voltage" means the box is NOT drawing current As I said earlier check the box grounding. "Wiggle test" all connectors

    2...The dist / trigger problems. You can check part of this quickly. First do 1 above and make sure the coil is drawing current. Then separate the dist connector and take the engine harness half, not the dist. half. With the key in "run" tap the bare terminal of that connector to ground. Each time you do so, one hot blue "snap" spark should jump from coil wire to ground

    "Rig" or buy a test gap. Do NOT test the coil for spark using the resistor coil wire. "Rig" a solid core wire. So long as it's "spaced" you can use any kind of wire.
     
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