jonesolds442

Hi fellow rocket enthusiasts,

My '70 Rallye occasionally dies; no sputtering, just dies as if the ignition is shut off. Clearly a sign of a flat short, right? Have any of you encountered this problem often enough to suggest which part(s) of the circuit, when the key is on, that is/are most prone to resulting in a flat short? For isntance, is there part of the circuit that is next to a sharp part of the frame/housing that may, over 42 years, lead to an eventual wearing-through of the sheath of the wire, thereby increasing the liklihood of a short?

I'm not excited about the inevitable divide-and-conquer sequence of wire-checking ahead of me, but if any of you could suggest certain areas of the circuitry to check first, I would appreaciate it tremendously.

My442

Do you have a wiring diagram?

You need to trace the 12 volts that eventually ends up at the coil.

Suspects: ignition switch, engine harness

A bad connection at the fusebox can do this as well.

The fact that it does this when driving suggests a marginal connection in the curcuit.

jonesolds442

Yes, I have a wiring diagram. I will investigate per your suggestions.

Thanks My442.

brown7373

Might be a bad wire and not a short. Years ago I had a 69 GTO that would just shut off. Long story short...the primary wire to the points had been cut almost in two, with insulation on one side holding it together. When the wire strands made contact, it ran. When vibrations caused it to lose contact it shut off. It was hard to find because everything checked out when it was making contact. Sometimes it would run for weeks, sometimes it would shut off 5 times a day. Back in 1972 it cost 80 cents to replace that wire!

sicky olds

I had a similar problem on my H/O... If you lose ALL power i would check what i did on mine. The main wire going into the firewall. The tar or whatever that material was to hold those wires in ended up loosening up from age. Just cleaned up the connections and gooped it up with black RTV to hold it in place and it runs great since. No cutting out.

droldsmorland

If you still have the original points distributor start looking at that. As mentioned above the points lead which comes up through the bottom of the housing is known to break because the breaker plate moves with the vac advance can. So inspect all the primary (small) ignition wires for evidence of corrosion and breakage. Look at the pionts and condenser wires and replace if suspect. Test the coil with an ohm meter. Clean all grounds. Lift the hood at night or in a dark garage (briefly please exhaust fumes dont take long to kill you, we dont want to read about you in the obits) and look for arcing.

oldcutlass

Which distributor do you have? Are all the connections tight and clean. The next time it fails, check the supply voltage to the coil. If it's missing you need to work your way back. If it's there it's either in your coil or distributor.

White_Knuckles

Shorting is a short circuit to ground where a wire or connection finds a ground path due to insulation breakdown or an exposed connection touching something and grounding out. Yes, it would kill the ignition but should blow a fuse before wiring smokes. Shorts don't heal themselves they blow fuses.

You most likely are experiencing an open ignition circuit such as loss of 12V to the coil or an issue with the points. The key switch is unlikely or you'd notice issues wiggling it and having the car cut out. I like the other posts pointing to the coil/points wiring.

There is a deal with these old fuse boxes where the fuse clamping blades (front side) are loose on the mechanical connection to the (back side) block wiring. Clip a voltmeter to the load side of the ignition fuse and with the key on, wiggle the fuse (with a plastic probe) looking for little sparks or opens (000) on the meter set to 20VDC range. I had my brake light circuit cutting out and this was the culprit. There are "add a fuse" inserts and taps available to correct for this. You will need a dedicated fuse for this circuit.

RALLYE KID

My rallye use to shut off when you where driving it. As soon as it cool off it started right back up. I had a bad coil.

compedgemarine

on a 442 I had years back it would randomly shut off. took a while to find but turned out that the tach wire was worn thru and would ground out killing the ignition.

jonesolds442

Thank you to everyone for the detailed analyses. Just for clarification, this in an 84k car that has never been apart with all the factory equipment. I have done a full tune-up, along with replacing the coil assy. I will start whittling-away at all the suggested causes. Thanks again.