mysterious carburetor problem

[sbaron]

I have a 1967 Chrysler Newport Custom which I call Carzilla.

I've owned it for 18 years. Its a great car.

Here's the problem I've been having:

Out of the blue, after running fine, I park for a short while, for an appointment, restart the car, it has trouble starting, sputters, backfires, blows out the muffler, dies. This has happened

a few times. Here's the mysterious part: The second time, after replacing points and seeming fine---it does it again. Won't run. No power---I wait, leave the car on the street near my house,

come back a bit later, start it again, manage to get it over to my studio a block away. I call to see about getting it in with my mechanic, then the night before, I try it and it starts up, has full

power, like nothing happened. I drive it home, no problem. I don't bother taking it in. I drive it around for a few weeks without incident. I take it 40 miles to an airport, park it, go on a trip, come

back, start it up, try to drive home, a rattle becomes a loud grind--- ball joint! I have to pull over and call for a tow.

My mechanic fixes the ball joint, which is great--a slight road noise is quieter, and a squeal in the power steering that its had for a while is gone!

Now hear comes the really mysterious part:

Its running great. My wife and I go up to Cleveland (40 miles) for an art show. Its raining so I've got the wipers and lights on. We go to the exhibit. When we come back, I see that I've left my

lights on. Bummer. We get a jump, it starts fine, seems fine, we take off. We get on the freeway, lights are on, wipers are on (its raining again). Suddenly its running rough, sputtering losing

power, stalls. I start it up and continue, but its running rough. It backfires and blows the muffler out a second time! I give it gas it wants to stall. I back off, get off the freeway, try to keep it

going, but I see its dying. The lights won't stay on. It conks out. The battery's dead.

Okay. We have to get towed back to Akron. Lousy night out. I have the driver leave it on the street beside my house.

The next day I charge the battery. I want to pull it up into my drive. I believe its going to start up and run just fine, which it does, like nothing happened; except of course, the muffler is

blown.

Now I have a theory:

If it were a carburetor problem, it wouldn't disappear for 3 weeks, run fine, then suddenly appear again. Twice.

I believe, if the battery hadn't run down, it would have started and got us home without any problems.

I'm thinking that the battery having run down, couldn't take the added pull for the lights, wipers (having just been jump-started)

and my attempts to keep the car going added too much gas into the carb, which was failing respond due to the battery failing,

which caused it to choke up and misfire, and finally the lights not staying on told me the engine was dying.

I think my problem may not be the carb at all, but the battery, or alternator, or both.

I thought I might run this by some real motorheads and see if I'm onto something or simply need to rebuild the carburetor.



Joe

 

[david hill]

Definitely electrical. Check wiring connections at the bulkhead at the firewall. Do a voltage drop test starting at the fuseable link. Corrosion and burnt / bad connections can cause your symptoms. Possible sources to check, bad ignition switch or points and condenser.

 

[Big_John]

Most carb problems are electrical.

I'd say you have some ignition issues. Because of the last failure in the rain, I'd look for some sort of moisture issue, like @david hill mentioned, wiring connections are easy to check. Also look under the distributor cap for moisture (it may have dried out by now) and carbon tracking. Check plug wires too.

Regarding the battery/alternator. That won't cause the running problems you're having. After jump starting, you should have been able to drive it home though. How old is the battery? A quick check of the charging system can be done with a voltmeter (Harbor Fright has a cheap one) . You should have at least 12.4 volts with the car off. Start the car, should have 13.5-14.5 volts at a fast idle. Turn on the lights and see if it drops off.

But don't just replace the battery or alternator without doing further testing. Or any other parts for that matter.

 

[CBODY67]

In what @Big_John has said, you could well find the issues. Getting your mechanic to do a "charging system check" as is and then do it after the terminal and contact cleanings, you should see that it was terminal degradation which could be the hidden issue. That load check diagnostic (with the engine running at fast idle) will check alternator output, battery condition, etc. as things are happening. Which can be better than the individual checks done by auto supplies on alternators and batteries alone.

On that drive home, after the jump start, the alternator was doing its best to re-charge the battery and keep the accessories running. Degraded terminals and battery post connections were hampering that process by resisting current flow back into the battery. Even under ideal daytime conditions with no accessories running, getting a decent re-charge from the alternator can take a good while from a dead battery.

Get the load check done, before and after the terminal cleanings. If the alternator is weak, not a hard deal to change. What size battery did you get?

I chased a problem on one of my cars. Sometimes it would start fine, but if I stopped and let it sit a while, it would not start or do anything when I came out a short time later. First time was one night when I was slowing for a stop sign, I heard a motorboat engine sound from the radio as the rpm started to fall. I throttled into the engine against the brakes to keep things going. That was my signal. Didn't happen again that night, but did several times in the future. But the no re-start issue was not good. After sitting a while, no problems.

Finally, I got a volt meter and started checking voltages. When the issue was happening, I was losing about .3volts in the ground cable. A minor amount, but enough to keep some things from happening. Must have been something flaky internally.

One day, I got into the car to go home for lunch. Curiously, the a/c blower motor was not working. When I drove up and parked (about 10 minutes later in the spring of the year), I got out the meter and started to check voltages. No significant issues. As the engine was running, I heard the blower motor relay click and the motor started to run. The .3volt loss had disappeared. Ordered a new ground cable from the battery and fixed that issue.

Just some thoughts and experiences,
CBODY67

 

[Fury1969WI]

As established, this seems like an electrical issue impacting both charging and ignition (blowing out the muffler = raw gas in the exhaust). I wonder if you've gone over your coil wiring and ignition cables recently? Won't cost anything and in my experience with this sort of muffler blowing up deal my hunch is you find something broken, loose, or corroded. Might not be the total cure, but something sound amiss there (pun intended).

 

[volksworld]

were the lights still on when you came out of the event? or was everything completely dead? if there was any juice left in the battery the alternator should be more than capable of keeping everything running for the ride home...I really think you're dealing with more than one issue...you really didn't state how far you drove it before it conked out so I have no way of knowing if it was running long enough to get the battery charged up enough to crank the starter, but ,again, it takes very little juice to run a points ignition system so you should have been ok to keep running...SO....if it wasn't charging it could be as simple a a glazed belt slipping on a wet pully...the circuit charges through the ammeter so you could have issues at the ammeter connections or at the bulkhead connector at the firewall (plenty of content here about this issue and potential bypass strategies)...or alternator or regulator themselves bad ...but I dont think this was causing it to run bad...now, as far as running bad in the rain, electricity takes the shortest path to ground so bad wires will allow the spark to jump through the insulation to the nearest metal or each other, and the presence of water or moisture in the air will help this happen more easily than if everything was dry...as John said same deal with a bad cap...other possibilities a bad coil, condensor or ballast resistor which will give a weak or intermittant spark...all this stuff could have been borderline functional to begin with and the rain could have just made the situation worse