1984 Mazda B2000 no spark

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Midnite from 10W40.com
1984 Mazda B2000 no spark Posted 6-10-2003 01:05

Just bought a 1984 Mazda B2000. Drove it 325 miles with no problems at all. The next day, it wouldn't start. Found a no spark condition to the distributor. Replaced the ignition coil, distributor cap, rotor, control module and the pick-up coil. Nothing helps. I read 9.50 Vdc at the primary inputs to the ignition coil when the ignition switch is on. I bought the Haynes Repair manual but it is no help at this point. Any advice or suggestions would be very helpful. Thanx
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Harvester [guest] from 10W40.com
1984 Mazda Posted 6-11-2003 20:05

Are you finding the same voltage on both sides of the coil? If so, it seems that the ignition module is not switching properly. With the key on, engine stopped, the module should be either fully on or fully off. If the module is fully on, you should find about 1 volt at the coil (-) terminal, but less is better. If the system is fully off, you should find about 12 volts on both coil terminals. The 9.5 volts is an odd value, which might happen if there is high resistance between the coil and battery, or between the coil and the module. Disconnect and reconnect all the terminal connections you can find, and try turning the ignition switch slowly on and off several times, or wiggle the switch and watch the voltage while you do so. If the voltage varies when you wiggle the switch, or the value is different each time when the switch turns on, it would indicate a bad terminal in the switch. Also, check the voltage on the coil (-) terminal while you crank the engine. In an ideal world, you should see 5 - 6 volts on that terminal with the engine cranking, but the design of the module will determine what you actually measure. Regardless of the module design, you should see a fairly large change from the key on to the cranking level. Before you go too far with taking anything apart, make sure the distributor shaft actually turns when you crank the engine. The timing gear/belt/chain is a prime suspect if the distributor shaft doesn't turn. There is likely more to your situation, but see what you find with these checks. Hope this helps. Keep us posted.
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Midnite from 10W40.com
Incorrect voltage readings Posted 6-13-2003 00:54

I read my voltages incorrectly at the ignition coil. With the key off, I read 0.02 Vdc from the (+) and (-) terminals to ground. With the key on I read 11.5 Vdc from (+) to ground and 1.8Vdc from (-) to ground. I do not yet know what I read when the engined is cranked as my battery is almost dead. I need a jump and will let you know more. Thank you for your input. It is greatly appreciated!
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Harvester [guest] from 10W40.com
84 Mazda Posted 6-13-2003 15:53

Those voltages sound better. The 1.8 seems a little high, but may be alright. Those readings also indicate the ignition module turns on with the ignition switch, rather than waiting for a distributor pulse to make it switch. Or the module could be shorted, but since you already changed it, that possibility is pretty remote. The cranking check will help determine if module is switching as it should- when you get the battery back in shape. Sounds like progress, so far- keep in touch.
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Harvester [guest] from 10W40.com
84 Mazda Posted 6-13-2003 15:55

Those voltages sound better. The 1.8 seems a little high, but may be alright. Those readings also indicate the ignition module turns on with the ignition switch, rather than waiting for a distributor pulse to make it switch. Or the module could be shorted, but since you already changed it, that possibility is pretty remote. The cranking check will help determine if module is switching as it should- when you get the battery back in shape. Sounds like progress, so far- keep in touch.
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Midnite from 10W40.com
Mazda no spark Posted 6-29-2003 18:20

I tried jumping the truck and still no spark. With the key in the on position I'm reading 12.5 Vdc to grd from the (+) of the ignition coil and 2 Vdc from the
(-) input to grd.When I turn over the engine the 12.5 Vdc starts to drop off. The 2.0 Vdc on the (-) ignition coil goes to about 1 Vdc. I don't know what to try at this point. I do appreciate your help!
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Harvester [guest] from 10W40.com
1984 Mazda Posted 7-1-2003 00:03

It sounds like the ignition module is not switching. Make sure the distributor shaft actually turns when you crank the engine- if the distributor shaft doesn't turn, nothing works. Also, make sure the distributor connections are good- no loose pins or loose connections and the like, and nothing got caught up in the rotor and broken somewhere along the way. If all that seems to be in order, disconnect the negative side of the coil from the ignition module, then see if you can get a spark from the coil secondary if you manually connect and disconnect the coil (-) terminal and ground- but watch out for a shock if the ignition primary circuit is working. If you get a spark from the secondary, it would indicate that the ignition module is not switching the primary current. I don't know if that truck has an on-board computer, but the ignition module might need some other signals, maybe a sensor signal, before it starts to work. On the coil (+) terminal, you should find approximately battery voltage (cranking voltage) when you crank the engine- a little less would be alright, but something above 6 volts for sure. Maybe someone else can add some details about sensors and the ignition system. Hope this helps, let us know how it goes.