Hot Rod Forum banner

SBC ignition problem

8K views 15 replies 5 participants last post by  chevy302builder18 
#1 ·
So I just got done rewiring a 76 corvette, and everything has gone smoothly until I went to start it. Now mind you; the car ran fine when I parked it at the beginning of summer and the only reason it was being rewired is because I had rewired it before when I was still learning and had a lot of poor craftsmanship. I used a generic painless universal harness. When I turn the key the engine cranks just fine, but i don't appear to have any spark. I checked the voltage on the +coil wire and it reads 12 V. I have the ground on the HEI going to the choke's ground on the carburetor (though I did also try a different ground when I was troubleshooting). From what I can see, everything is working the way it should but I can't see a spark either with the plug or with a socket shoved in the wire boot. So far I have swapped out the ignition module, cap, and coil but nothing has got it to fire. I've now become more certain that it must be my wiring, but I have no idea where to look next. An HEI only has 3 wires going to it correct? (tach, coil, ground?) I even checked the +coil wire's voltage as I turned the key to "start" to see if the voltage was cutting out of something, but no dice. Someone please help!



Hammer :evil:S
 
#3 ·
what was wierd is i learned something about the HEI and older coil in cap had a blue clamp running off a brown wire one of the three wires running to the cap.. It was a green wire, and i really dont know what this wire does. but i made sure that this wire was hooked up after changing distributors. its a blue clamp piece that joins the green and brown wire together by exposed wire, but this is based off my old chevy pick up around the same year.
 
#7 · (Edited)
I'm not following you on the choke ground wire. The choke heater is grounded through the choke housing to the carb body, intake, cylinder head, etc. on through to the battery, no ground wire needed. The only wire required at the choke itself is a 12 v current carrying wire.

The ground on the distributor is connected to the coil on one end and the body of the distributor on the other. The rest of the ground pathway is through the dist. body through the clamp and bolt into the engine block, etc. on to the battery eventually.

As for the power supply wire having a splice in it (if that's the case), I would caution you against using the coil power wire to run anything else. The HEI needs full battery current to work at its best.

Be sure there is a male terminal in the center position in the coil cover that mates w/the female 3-wire connecter/pigtail that's attached to the distributor. That's the ground for the coil. The way the ground is made, it can be accidentally left off. It will be either a wire or solid metal conductor running to one of the coil holddown screws. If it's left off, the coil will not be grounded.
 
#8 ·
When I said its grounded on the choke's ground, I was referring to a Summit aftermarket carb that has a 3-4 inch wire coming from the choke housing to another screw on the carb (grounding it to the manifold, cylinder heads, ect) I ran a wire from the center pin on the HEI (the ground) and ran it to that same screw to ground the coil, but its not appearing to be working. I then grounded it to the terminal on the alternator to be sure my ground was good, but had no luck. Everything says its a bad ground, but I can't figure out how it could be bad.
 
#10 ·
I'd run a temp jumper from the neg post on the battery to the neg terminal on the dizzy and see if it starts.

If it doesn't, I'd leave that one in place and run a seperate jumper from the pos post on the battery to the pos terminal on the dizzy and see if it starts. (You'll have to pull the jumper to kill it)

if it doesn't run "hot-wired" then you have an internal dizzy problem. When you did all that swapping out did you put the carbon coil transfer pin, It's that pin that connects the coil to the cap normally has a spring and a rubber washer and needs some di-electric grease on it.
 
#12 ·
I'd run a temp jumper from the neg post on the battery to the neg terminal on the dizzy and see if it starts.

If it doesn't, I'd leave that one in place and run a seperate jumper from the pos post on the battery to the pos terminal on the dizzy and see if it starts. (You'll have to pull the jumper to kill it)

if it doesn't run "hot-wired" then you have an internal dizzy problem. When you did all that swapping out did you put the carbon coil transfer pin, It's that pin that connects the coil to the cap normally has a spring and a rubber washer and needs some di-electric grease on it.
Yea I got the transfer pin in there. I'll try running a jumper ground to the batt and sees what happens. And Cobalt: I used a universal harness, so I have no actual 3-pin connector to plug into the distributor. Just 3 separate wires (coil, tach and my separate ground. feel me?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top