Hello! I've got a small block chevy that won't get spark. I changed the carb and intake and now I can't get more than two sparks on my tester when I'm cranking. I have this problem with both a pertronix conversion and good old timey points. New ballast resistor, new points, new cap and rotor. I have three coils, a brand new one,one that ran last year, and a spare I keep around. All three vice the same result. Wires check out OK. 12.46 volts at coil when cranking. I checked the run position with a test light, there's power there. I hooked the distributor to the test light and got it to flash when the distributor shaft is turned. I put the distributor in, crank it over, get two arcs and, that's all. What am I overlooking?
What do you mean by two arcs? The coil fires twice, all the plugs fire twice, or only two plugs fire?
I would run a wire from the positive side of the battery to the coil, This will help in determining if it is before the coil or after. Vic
Thanks, guys. I hadn't considered the switch, because the starter turns over and that means it's good right? Nope. Gonna hot wire it right after work. I'll let you know if that's it. Back to the 50s is only 3 days away and this happens. THANKS!
You gotta double check EVERYTHING these days- electronics from "South of the Border" can be junk right out of the box! Good luck!
Actually we have been running on Mexican parts since the '80s. Nothing in the world wrong with Mexican parts, what is kicking our ass is their Asian competition.
Good idea. I didn't post a solution because anything I would do has pretty much been covered. But it would be good to know the outcome.
the points plate inside the SBC distributor needs to be grounded....Chevy did it with a small wire. i have seen them broken , thus not completing the circuit
Yep. ^^^^I have also seen the power wire loose its insulation and the points ground them selves out. I got a window distributer in the garage that I have to replace the power wire now come to think of it. Thanks for the reminder.
A real old guy told me 40 years ago ,most electrical problems are due to bad ground. I've remembered this and he was right.
Sounds like it could be the IGN 'RUN' position is faulty. If you get spark when cranking, but not when in 'RUN', the IGN switch could be at fault. The coil gets power when cranking from the starter, then it switches to power from the IGN switch. Cosmo
It's the switch. I ran a 16 ga. jumper from the battery to the positive coil terminal and it fired. Just like Vic and the rest of the guys said. Now I'm going to have to chase down a switch and dial it in. Before Friday. Thanks everybody. See you at Back to the 50s.
Glad you found this. The weirdest thing I've seen like this is a Pontiac points distributor in a vehicle that would crap out at a specific rpm. It turned out the wires in the dist to the points were too short and the vacuum advance had pulled one of them apart inside the insulation - when the vacuum changed, the wire kind of hooked itself back up. Only found it on a Sun distributor machine - wish I had one now for my flathead's Roto-Faze distributor.
A reminder to all of us. Back to the basics and the obvious. Thanks for letting us know the solution. Ben
Just don't assume the new switch will be any good either. We went through 3 new, out of the box, ignition switches (from 3 different parts houses) on my son's car before we got one that functioned! Though all 3 switched were boxed differently, all looked to be of the same crappy manufacturer. We are not putting a lot of faith in this new one either, we have rounded up an old nasty looking used thing, and its in the glove box as a backup. Gene
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