where to start..

Matt Conlan

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Driving along at about 60 in 1970 383 Newport, coasting down a hill, heard a large thud, and the motor just stopped. No backfire or anything. Just shut off. Drifted to the side of the road and popped the hood. No leaks, drips, anything obvious. On trying to restart, it sounds like it would if, for example, a spark plug wire is out. It rumbles for a couple cycles but doesn't start. Just got it home, and am thinking about it. Figured I'd throw it up on here to see if people had ideas where to start. Could the thud be coincidence?
 
The "thud" doesn't sound encouraging however I'd check the usual suspects first like the fusible link, loose coil or other wires, grounds, alternator connections. Something similar happened to me in the the Monaco albeit not at highway speeds. Fusible link was the culprit.
 
The fusible link is still good because if it failed you would have no power to the ignition or to energize the starter solenoid.

"Thuds" are never a good sign. The obvious culprit would be a failed timing chain. But check some other things first: Check you distributor and be sure it is tight in the block. Remove the air cleaner and look down the carb throat to see if you get a squirt of fuel when you move the throttle. Pull the coil wire and place it about 1/4" from the block and see if you have spark when the engine is turned over. Now, line up the timing mark to TDC. Remove the distributor cap and note which plug wire the rotor tip is pointing at. If it is point at #1 or #6 the timing has not changed and the chain should be ok.

How many miles are on this engine and how long since the last tune up. Has this car been converted to electronic ignition? Check these items and report back.

Dave
 
Thanks guys. Only 78,000 on this engine. I tuned it up earlier this summer and set the timing. It does have a pertronix electronic ignition. The engine actually sounded like it had a timing prob to me when I tried to restart. like a piston was missing, but there was no backfire.
 
Thanks guys. Only 78,000 on this engine. I tuned it up earlier this summer and set the timing. It does have a pertronix electronic ignition. The engine actually sounded like it had a timing prob to me when I tried to restart. like a piston was missing, but there was no backfire.

Check for spark. Might be a dead pertronix unit.

Dave
 
Hope so. Any idea of the clunk? It sounded like it came from the back of the car. I actually looked as we were driving because I though I lost something.
 
Hope so. Any idea of the clunk? It sounded like it came from the back of the car. I actually looked as we were driving because I though I lost something.

Might have been a light detonation of unburned fuel. Get it running and see if the clunk happens when coasting down a hill again.

Dave
 
On trying to restart, it sounds like it would if, for example, a spark plug wire is out. It rumbles for a couple cycles but doesn't start.

If it's "rumbling", that means you must have spark. So that may eliminate the ignition as a cause.

I would check for gas. Easiest is to look down the carb and see if the gas squirts out of the accelerator pump nozzles. No squirt? Spray a little starting ether down the carb and see if it fires. If it does, unhook the gas line, run a rubber hose to a soda bottle and crank the engine over. It should fill the bottle pretty fast.

The "thud" is disturbing though... If the gas checks out, pop the valve covers off and see if everything is going up and down when you crank the engine.
 
Chrysler timing chains have nylon teeth in cam sprocket/gear. If the teeth broke off, which they will eventually, the cam is not turning. I suggest pulling the distributor cap and watching the rotor while a friend tries to start the car. If the chain is OK, the rotor will turn. If NOT, you've probably got a timing chain replacement ahead.
 
x2 on the timing chain. Mine failed while on the freeway, there was a subtle 'thud' then the motor just went dead. Didn't sound normal when cranking it.....
What actually happened with the chain is it slipped a tooth or two. I was still turning the cam gear but totally loose as the nylon had mostly come off.

440 Rebuild & Upgrade
 
Here's the report. I'm getting a spark from the coil. The engine turns freely by hand. The rotor turns with the engine, TDC lines up with #6 plug wire. There's gas in the carb, and when I start it, it will start, run for a few seconds, and then "burp" the gas in a fountain out the carb and stop.
 
x2 on the timing chain. Mine failed while on the freeway, there was a subtle 'thud' then the motor just went dead. Didn't sound normal when cranking it.....
What actually happened with the chain is it slipped a tooth or two. I was still turning the cam gear but totally loose as the nylon had mostly come off.

440 Rebuild & Upgrade
So you were still able to turn the motor and the distributor rotor turned with it, even though the chain was bad? How did you determine it was the chain?
 
On a related note, this was connected to the positive terminal on the ignition coil. The wire had been pulled out. I'm embarrassed to say I don't know what it is. Some kind of capacitor or resistor?

newport.jpeg
 
Here's the report. I'm getting a spark from the coil. The engine turns freely by hand. The rotor turns with the engine, TDC lines up with #6 plug wire. There's gas in the carb, and when I start it, it will start, run for a few seconds, and then "burp" the gas in a fountain out the carb and stop.
Stuck needle and seat or float. Basically it's letting too much gas in.

That would be your problem.
 
On a related note, this was connected to the positive terminal on the ignition coil. The wire had been pulled out. I'm embarrassed to say I don't know what it is. Some kind of capacitor or resistor?

View attachment 400900
Capacitor for AM radio static. Has nothing to do with your problem or how the car runs.
 
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