340 Keeps Shutting Off When Driving

[JMF]

Hi guys, I have a 73 Challenger with a 340 and every now and then the car just shuts off when driving, not in a fuel starvation spluttery kind of way but just an instant shut off.

- It does it most when coming to a stop at the lights so initially I thought it only shuts off when braking but today it shut off when driving along without braking.

- Always starts up again no problem

- Only seems to happen when the car is driving/moving, I can never get it to shut off when just sat stationary in P or D

- Can't predict when it's going to shut off, eg doesn't shut off everytime, seems to get better once the car is warmed up although I can't say for sure.

- Since i've had the car it's had a problem with the iginition where when first starting the car none of the gauges , indicators or wipers work but if I turn the ignition back towards me slightly they all start working again, so I thought it might be related to that but I've tried wiggling the ignition when the car is running to get it to shut off but it never does so i'm not sure that's it.

I had an electrician look at it and he tidied up some old wiring but it never fixed the problem.

Any other ideas where I could start looking ?

Here is a pic of my engine bay rather than me go through what my setup is...

Thanks a lot for any help

[justcruisin]

Sounds more like an ignition issue. You will need to do some on road diagnosis. I would try running the car with a wire hooked up to the input to the ballast via a remote switch direct from the battery + , this will check your ignition switch and wiring to the ballast. If you have a spare igniter box, distributor, ballast and coil, swap them out one at a time.

When it cuts out, without touching anything, try your indicators and check if you have gauges.

[GreenMachine]

1st step would be to check grounds on the firewall. It looks like fairly new paint, may need to take the ignition module off and wire brush around the bolt holes. Same with the voltage regulator. Do the easy stuff first.

[Kern Dog]

My 75 Power Wagon has a condition where if I twist the key to start it, the key/lock cylinder sometimes does not spring back into the correct position. When this happens, the temp and oil pressure guages do not register. The engine stays running but you may be onto something with your ignition switch. The part where the key fitsis not the switch, it is merely a lock cylinder. Inside the column is a mechanism that the lock cylinder slides into. It is spring loaded and is supposed to allow the key to snap back to the RUN position after starting. In the case of a worn or defective mechanism, I'd suspect that your problem may occur. I have seen some feel really sloppy, as if whatever spring fitted inside had busted to bits. Imagine the electrical system trying to function with the equivalent of a power tool half hanging out of the wall socket....

[Troy]

My 70 Challenger would randomly do the same thing. It had multiple issues but the cutting off while driving ended up being a loose wire at the bulkhead connector on the engine side. It was a new engine harness so I wasn't inspecting it as carefully as everything else. I also had a loose wire on the ignition switch to bulkhead connector so it made tracing the problem really exciting! At this point I have a new ignition switch, new dash harness, and another new engine harness BUT I drove it for a while with jumper wires and a bypassed ballast resistor to verify that I had found the right spot. This is a great way to burn up a coil or ECU so it's not recommended! But it got me home a few times instead of being stranded on the side of the road.

Troy