No spark

[BillgreenC10]

Driving along, truck just shuts off.

Cranks, but won’t start. It’s a 72 with a 350 and HEI Distributor. Put on spark tester, nothing. Jumper wire from HEI to + battery terminal, starts right up.

Put in a new ignition switch, nothing. Typical hot mess of wiring from previous owners.

Any ideas?

[franken]

Time to get out the voltmeter and see if/why no power is getting to the HEI. It isn't time to randomly swap parts such as the ignition switch.

[BillgreenC10]

Like what and how? I am an electrical idiot. I have a volt meter, but I don’t even know what setting it should be on.

[franken]

google.com
How do I use a voltmeter?
What is Ohms Law?
How do I TS an ignition issue?
How do I troubleshoot?

The internet will provide a million responses in a tenth of a second. Why are you waiting hours for the rest of the world to imagine what the trouble is?

Electrical circuits are simple. Current goes from the source back to where it came from.

Saying you're an electrical idiot isn't an excuse. You have a problem and want to solve it. Do so. Trace the lack of voltage back to where it stops being supplied.

[Dead Parrot]

Unless you have lots of money for random new parts, this IS a good time to learn how to use that Volt meter.

Your jumping +12 from the battery did remove failure of the HEI dizzy from the mix.

Trace the normal power wire back from the dizzy to where ever it goes. Does it now have +12v? Maybe a splice from a PO came loose. Or mouse activity. Also possible whoever swapped in the HEI used the old coil resistor wire to power the HEI and it finally quit working on the lower voltage. They want full battery power.

Under the dash possibilities are loose wires and bad/out of adjustment Neutral Safety Switch.

[BillgreenC10]

Originally Posted by Dead Parrot

Unless you have lots of money for random new parts, this IS a good time to learn how to use that Volt meter.

Your jumping +12 from the battery did remove failure of the HEI dizzy from the mix.

Trace the normal power wire back from the dizzy to where ever it goes. Does it now have +12v? Maybe a splice from a PO came loose. Or mouse activity. Also possible whoever swapped in the HEI used the old coil resistor wire to power the HEI and it finally quit working on the lower voltage. They want full battery power.

Under the dash possibilities are loose wires and bad/out of adjustment Neutral Safety Switch.

I don’t, I do have time. I did trace it back, the truck has a Tach, wire going to distributor is Brown and it goes to the back of the Tac hand then it has a V shaped plug that goes to a spliced connector to the fuse box into the “unfused” slot.

The tach was acting wonky the last few times I drove it, bouncing around instead of holding steady.

Thanks for the reply.

[RustyPile]

Originally Posted by Dead Parrot

Unless you have lots of money for random new parts, this IS a good time to learn how to use that Volt meter.

Your jumping +12 from the battery did remove failure of the HEI dizzy from the mix.

Trace the normal power wire back from the dizzy to where ever it goes. Does it now have +12v? Maybe a splice from a PO came loose. Or mouse activity. Also possible whoever swapped in the HEI used the old coil resistor wire to power the HEI and it finally quit working on the lower voltage. They want full battery power.

Under the dash possibilities are loose wires and bad/out of adjustment Neutral Safety Switch.

OP admits he doesn't have much electrical knowledge.. Let's be very careful and extremely accurate with our instructions.. He states that motor cranks over, just doesn't start. Also, he states when he installed a jumper directly to the HEI, the engine starts and runs.. That rules out the neutral safety switch AND HEI distributor as a problem.

[Getter-Done]

Originally Posted by franken

Time to get out the voltmeter and see if/why no power is getting to the HEI. It isn't time to randomly swap parts such as the ignition switch.

Originally Posted by franken

google.com
How do I use a voltmeter?
What is Ohms Law?
How do I TS an ignition issue?
How do I troubleshoot?

The internet will provide a million responses in a tenth of a second. Why are you waiting hours for the rest of the world to imagine what the trouble is?

Electrical circuits are simple. Current goes from the source back to where it came from.

Saying you're an electrical idiot isn't an excuse. You have a problem and want to solve it. Do so. Trace the lack of voltage back to where it stops being supplied.

You are A great ASSet to this forum.

I always look forward to your Great Positive comments.

You are the Best.

[Richard]

An old school ignition kill/antitheft is to ground the tach wire. Make sure yours is not grounding out while driving.