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Won't start (Crank, no spark)

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  • Won't start (Crank, no spark)

    This past week a buddy and I were 3.5hrs into a trip when our 71 Chevelle abruptly died. We were cruising along at highway speed then traffic slowed and at that time the engine died. A few things we noticed as it happened. I heard an unusual clicking noise coming somewhere from the center of the vehicle towards the front. Wideband O2 displayed very lean condition (~19) as the engine surged a bit. We were able to pull off and shut the engine off. That all happened in a few seconds. We started to troubleshoot and found that the fuel pump runs, fuel was available at the rails, but had no spark. Also to note when we pulled a plug it looked great but had no fuel? I would expect that after cranking the engine and no ignition that the plug would have fuel on it. We were towed to a parts store and replaced the ignition coil but still no spark. Thinking now it could be the Hall sensor?

  • #2
    If you determine the dist is faulty.

    This is available:

    https://www.summitracing.com/parts/edl-3614

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    • #3
      test the output from the dissy. most likely hall sensor
      https://www.digikey.com.au/product-d...1002-ND/374780

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      • #4
        We also measured the input voltage to the cap. Seeing 12+V with key on, but after the fuel pump is done running it drops to 0V. Guessing that it needs 12V at all times. As soon as the fuel pump is done running it goes right to 0V.

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        • #5
          Easiest way to see if the distributor is the problem is to see if you get RPM reported on the handheld while cranking the engine over. If there's no RPM then you won't get spark or fuel.

          Originally posted by ecn113 View Post
          We also measured the input voltage to the cap. Seeing 12+V with key on, but after the fuel pump is done running it drops to 0V. Guessing that it needs 12V at all times. As soon as the fuel pump is done running it goes right to 0V.
          Look at the wiring diagram in the instructions. It's supposed to work that way because that's how the system is wired. The coil, IAC and injectors are tied to the fuel pump 12v circuit.

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          • #6
            Ok, checked the rpm on the handheld today while cranking. With key on it reads 220 (which is correct) and does Not change while cranking. So if the rpm isn't changing from the 220 default value does that point towards a distributor issue?

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            • #7
              that points to the hall sensor inside distributor

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              • #8
                Advice on testing if the hall sensor is bad? Check voltage output while cranking?

                The sensor itself is pretty loose. Atleast one of the mounting screws is loose but hard to get to because its under the shutter/lockout assembly. If I do have to replace the sensor can I remove the shutter/lockout assembly with the two visible nuts? Guessing my timing could get changed during this process if not careful.

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                • #9
                  unfortunately i cant find my wiring diagram
                  but there are 3 wires running to dissy
                  one positive
                  one negative/ground
                  one signal wire
                  test for battery volts between the pos and ground wires
                  then test between positive and signal wires
                  turning dissy slowly should see pulsed signal
                  if cranking will see maybe 3-5 volts
                  the hall sensor ouputs a ground signal

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                  • #10
                    Take the distributor out and spin it over with a cordless drill. Do you see RPM on the tablet?

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                    • #11
                      Ok, both of those suggestions are helpful, thank you. If the hall sensor does need to be replaced will the distributor need to be removed to replace it? I'm trying to avoid changes to the timing as much as possible.

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                      • #12
                        There won't be any timing changes if you do a good job of marking where the distributor was clocked at before you take it out. Reference the distributor body to the intake manifold and pop the cap off and reference the rotor to the distributor body. Once the distributor comes out, do not turn the engine over. When you're done testing or fixing the distributor, put it back in so your reference marks line up and it'll all be the same.

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                        • #13
                          Thanks everyone for your advice. Turns out the signal wire to the hall sensor board had broken off. I ended up soldering it in place. After reassembly it fired right up. So throughout this process I've obtained anew coil and anew hall sensor (not the board) and wondering if these are good items to keep around. Also debating if I should at some point remove the board anyway and re-solder those other joints. I haven't seen any threads describing wires breaking off the hall sensor board so wondering if this is common or not.

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                          • #14
                            If a soldered wired broke off at a solder joint, you might think about adding in some strain relief that keep that from happening again. You already have an extra coil and sensor - why not keep them around?

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