I was working on the Bird today, trying to troubleshoot the rat's nest of wires I inherited. Decided to finally pull the dash off. I unhooked all the wiring harnesses (the ones that actually were connected) and tested some circuits like the headlights by jumping to a red wire into the ignition switch.

Everything was going fine until I decided that the enigine was probably cool enough to do the radiator flush I planned on. Without hooking anything back up, but making sure all my jumper wires were completely disconnected, I cranked it up. And I heard something go POP, but the car kept on running. When I got my senses back I turned off the car (well, turning off the car amounts to flipping the toggle to the coil to "OFF"). A cursory glance in the engine compartment reveiled no fire or bits of anything scattered around. I checked the fuses, but none blew, which I was sure had happened with all my lose wires (and the 'duct tape' insulation on half the patches that were on the wires).

I was sure it was something like the starter solenoid frying or something equally catastrophic and bizzare. So I carefully pushed my momentary Radio Shack button (my "Key") and the engine started to crank (whew! not the starter). And crank. And crank. Stop cranking, give it two pumps on the gas. Crank. Crank. Ok, so I screwed up the coil or distrubitor? Oh no wait. Forgot to toggle the coil on.

All systems go now, I push the launch button and the engine whirs to life. Hurray, I overcame my own stupidity.... BAM! and the engine stops. The granddaddy of all POPs resonated from the engine compartment. I was sure the entire engine was a melted chunk of explosion. Somehow nothing caught on fire, but luckily if it had, the fire department was only 20 seconds behind the backfire. On top of that, being at the barracks, I had about 20 Marines screaming "IED!" and "Take cover!". Fireman Dan said he was surprised the air filter didn't catch fire. I had to ask him to repeat it because my ears were still ringing.

So thats the story, now the question. What the hell did I do to make it backfire like that? Assuming it was a backfire. It has only backfired once before and that was when I was testing the vacuum advance on the distributor with a miteyvac (the advance worked).

To warn you, the coil is hooked up to a battery line and the distributor, with a toggle switch on the battery line. The alternator is an SI type, and I was inspecting the area where the wires come together (green, red/black, black) because it was very suspect (before the backfire). Other than those two areas, I can't think of anything that would have changed in the car, except a few bare connectors were switched from duct tape insulation to electrical tape (thinking heater hookup, and oil pressure sender wires, not sure). Any ideas? I'm afraid to fire her up again, especially in front of 100 people

If you are running a points distributor, by bypassing the resistor wire in the harness you are providing too much voltage to the coil and points. That shouldn't make it backfire, though it will prematurely wear the points. Also check or replace the points capacitor when you are done playing, along with the one on the coil and the one on the blower motor. One of those may have popped. Perhaps loading the intake and cylinders with that charge of fuel before turning the ignition on made the big blast.

I drove a car for two weeks like that, pushbutton and toggle. Lights are overrated, anyhow...

Seems to work ok now. I'm just hoping it was the fuel. I'm not sure about the condenser, I'll have to check that when I can get daylight and a crack at the distributer. Luckily I don't have to worry about the coil capacitor because there isn't one. And also lucky because there isn't a heater. Well, lucky for now, not so lucky when I take this car back to Colorado in November. Since the lights weren't working anyway, I used the dimmer switch as a push-to-toggle for a jumper from the tan headlight wire to a red wire in the ignition switch. I'm sure my Bird is going become a true Firebird one of these days.

And I mean by catching fire from the insane wiring. Not a restoration.

Anyone have a complete heater box and blower they are giving away (somehow I have the heater controls...) ?

sounds like when you turn the ignition off whild driving down the road,than turning the ignition on after it has been off for a bit.KA-BOOOOOOOOOOOOOM!!!!!

Check if there's a loose vacuum line connection, either at the carb or behind the dash.