Lets play a game (ignition question)

[N2TRUX]

Ok, lets play a fun little game of "What did the dumb @ss blow up". It real simple. I'll be the dumb @ss, and you be the contestants trying to guess what I blew up. Be forwarned though, there aren't any lovely parting gifts for the loosers.

The scenerio goes like this. I bought a factory "tach" gauge cluster for my 77. I plan to have it restored because there is some fading on the gauge faces. I wanted to verify that everything worked before I called to get an estimate on the restoration.

I hooked everything up, but the brown "tach" lead wasn't long enough, and didn't have a plug on it. I used a jumper with alligator clips to reach the tach output on the distrubitor. Everything checked out good.

I asked my buddy that was helping me to unhook the jumper so I could pull the "tach" cluster out, and put the "non-tach" cluster back in. While putting the non-tach cluster in, I turned the key on to move the shifter down for clearance. When I did smoke rolled out from under the hood.

Since the tach lead is ground, I can only assume that my jumper must have landed on the positive lug on the firewall. The end result is my truck won't start now It turns over, but it won't start....

So what do you think I blew up?

[Russell]

Check the fusible link for the ignition system, probally blew it when you did that... I had a tach hooked up to my engine once while I was tuning it up, put the tach down and the positive touched the ground, stalled the engine right out, but she started up again...

[N2TRUX]

I had just started the truck right before this "incident" so I know it was running just fine.

Ok, here are a few clues-
I still have 12v on the (orange) hot lead going to the coil.
I do NOT have any spark at the plugs.
I DO have continuity from the tach lead on the coil to the positive side of the coil.

[87 STEPPER]

I dont belive there's a fuseable link in the ign. sys. wireing.

I think your truck has a ceramic ignition coil resistor that mount's on the fire wall i'd ck. that.

Remove it flip it over and look and see if it look's cooked.

You could also ck. it with a ohm meter to see if it has an open.

[Russell]

You're right, there is no fusible link... If the coil is good, but you've got no spark, then check that little resistor that 87 mentioned... The system isn't that expansive, so it shouldn't take too long to find the problem...

[1FaastC10]

isnt that little resistor part of a non-HEI ignition system? if so, his '77 will have HEI, thus not having the resistor.

[mike reeh]

ballast resistor? There is no ballast resistor on a 77 truck, especially not w/ HEI...

I dont know exactly how or why but since you had the jumper hooked to the tach lead, maybe you smoked the coil or possibly the module.. Its definately one of the two, if you have 12v at the distributor still...

Where did the smoke come from? The distributor? I would assume the coil would look/smell cooked if it was "smoked" but I think they're a little more durable than that.. I'll put $5 on the module being toast..

Mike

[87 STEPPER]

Well,

There go's that idea i couldn't remember what year HEI came into existance.

[Russell]

Yeah, my first thoughts were, fusible link, then coil, then fused wires... Further thinking crossed out fusible link and fused wires, so its gotta be the coil, or something related to the coil (as in that little module that hooks up to the coil)

[old Rusty C10]

my 76 has HEI and theres a hook up of some kind right ont he firewall its got two positive wires to it one comes fromt he ignition switch the other end i dont knwo where it goes but its held onto the firewall to the left of the wiper motor (looking from the front of the truck) its almost diamond shaped and is hled on with two small 1/4 head bolts check that its the only hot exposed thing i can think of

[N2TRUX]

mike reeh is correct. There is no resistor on the 77.

I inspected the coil when I checked continuity. The leads going in did get hot enough to expose the wire inside. The leads are also very oily, and have the distinct smell of a blown capacitor.

[SCOTI]

Ken, my guess is that if the wires were still hooked to the distributor & the power was turned on possibly causing a ground/short from a dangling wire, you cooked the HEI module inside the cap under the rotor. It's pretty easy to replace & new AC/Delco shouldn't be too much.

Check w/your bro-in-law (?..... I remember someone in your distant family was a mechanic) & see if theres a way to test the resistance on your existing module to rule it out.

Keep us updated.

[bigblock73]

I too think it is the module.

I bet that scared the crap out of you didn't it? Well, did the tach dash work at least?

[Russell]

Hehe, I do this kinda thing all the time, plumes of smoke coming from my engine compartment arn't too rare when I'm working on electrically related equipment :P

[N2TRUX]

SCOTI, yeah it's my Bro-n-Law thats a mechanic. I called him, and he suggested it was one or the other too

After seeing, and smelling the coil I feel pretty confident that it's toasted. It may have taken the module out too. I plan to replace everything while I'm there, but I'll do it one piece at a time just to find out which part (or parts) it was.

[N2TRUX]

Jeff, Yeah I freaked for a second when I saw a LOT of smoke rolling out, and I had a lap full of parts. Fortunately I kept a cool head and turned the key off.

Yes, I am happy to report that the tach cluster seems to work just fine. Thanks again for the lead...

[SCOTI]

I thought it was a bro-in-law. I do.... I do still have some cells left. Just remember when replacing the coil, it's real easy to leave the ground strap from the coil off (don't ask how I know.... or how often I learned this ). It will cause the same engine turns-but won't fire mystery.

[bigblock73]

No problem, just trying to help out.

Let us know what actually failed...I am definately curious.

[Crank]

SCOTI. Haha. I had that same problem trying to resurrect the '78 305 that was in my '67. It would turn over and get fuel, and I replaced all the bull**** to do a tuneup. The truck hadnt ran in 11 years and i didnt know much when i started. Little green wire left danglin off the thing after i replace the dist. cap and rotary button. put on the lil green wire and Ta DAAAA 11 year old carbon deposits lept to life. Haha. Smoked like a son of a gun for about a day. Sorry to get off topic, it was just fun. hehe
Brandon

[SCOTI]

Yep, it's happened to me a couple of times. I would be putting everything back together & the ground wire would either get overlooked or I wouldn't see it & it would be stuffed between the coil & the cap.

[N2TRUX]

Finally.... The rest of the story.

I have been pretty busy with the holidays, so it's taken a week to get my parts, and get back on my truck.

I bought a Brog-Warner coil and ignition module at Pep Boys. I had to go to O'rielly's for an AC/Delco cap, and rotor.

I put the new coil in the new cap, and installed the new rotor. I know this would have been the pefect time to put the ignition module in, but I wanted to see if it was the coil, or ignition module that was blown. My money was on the coil, because it smelled blown, and the lead wires were melted together.

I put everything back together (almost) and gave it a try. RRRrrrr. Nothing! It turns over, but no fire. Hmmm? I check my work and realize I have left the ignition wires from the module to the cap unplugged I plug them in, and still nothing. Hmmm? Must be the ignition module shot too.

Everything comes back apart, and the new ignition module goes in. Again, I put everything back together (almost). Do you detect a pattern? RRRrrrr. Nothing! It turns over, but no fire. Again????

I check the wires, and this time I plugged the wires from the module to the cap back in, but forgot to plug the power wire in. Ah-Ha! I plug the pwoer in, and I'll be darned if he didn't start.

Sooo, I will assume that the end result is both the coil "and" the ignition module that were blown. That is "assuming" I plugged everything back in on all my tests.

[1FaastC10]

Originally posted by N2TRUX
mike reeh is correct. There is no resistor on the 77.

mike is correct?! NOOOOOO... I was correct, i said it first. :p

[N2TRUX]

Originally posted by 1FaastC10
mike is correct?! NOOOOOO... I was correct, i said it first. :p

You are correct sir! I guess I missed your post and read his. Sorry...