Packard Forum Index » V-8 (1955-56)

Hi Guys. Have not a clue on this one. Was having trouble with my 56 Packard 400 where I would be driving then all of a sudden a big jerk like the engine was skipping or missing almost like out of gas then would come back running good.
This happened enough where i was very concerned with safety driving my car.

I replaced points gaped at 16, new cap,rotor,condenser,put new wires in the distributor as the the cloth seemed frayed,checked timing 15 degrees, still have the issue when it gets warm. Also new spark plug wires. Today I drove it about 20 minutes to my destination no problem. Coming home it started to jerk again and then backfired and put a huge hole in my muffler and resonator on the drivers side.

I did check the the mechanical advance seems to work when I put higher the rpms.

Please I need help with this. Looking into getting my distributor rebuilt car has around 96,000 mile on it.

Thanks

Gary

A sudden and intermittent loss of power to the coil could cause engine stumbling and a backfire. I remember back in the days of my misspent youth someone wanting to make a statement with a lot of noise could do a quick turn off and on of the ign switch to cause a backfire.

There could be a loose wire connection somewhere but 55-6 ign switches are somewhat overstressed and are known to have exhibited some strange failures or suddenly acted up. Since the coil is powered from its own terminal off the switch if vibration made that terminal suddenly lose its electrical connection then regain it that could be a cause. A switch problem might not be very evident because the rest of the car power comes off a separate terminal so you would not see lights go out or the radio quit if only the IGN terminal was faulty. Ballast resistors have also been known to become intermittent but usually once those fail it becomes permanent. Still worth checking though.

If the car has a push button trans then if it still has the auto park relay and there is no sign of the trans trying to shift into park when the problem occurs then neither item is as likely a cause. Even if the Ign switch or ballast resistor is ruled out coils have been known to intermittently fail and it could have developed a loose connection inside.

If you replaced the cloth covered wire in the dist with another of the same extremely flexible type and made sure the routing was correct so it could not get pinched and shorted then probably not an issue but replacing with ordinary hookup wire could cause some problems. Ordinary wire is not flexible enough so it can fatigue and break relatively quickly with the constant advance movement. Not sure if an intermittent connection there would cause a backfire but it could cause engine stumbling or even kill the engine if there is a break or a short and the condition lasted very long.

As Howard described, there is some intermittent connection in the ignition system which is cutting it off while the car is in motion and still sucking fuel into the carburetor which builds up for a few seconds, then ignites all at once causing the explosion. The ignition switch seems the most likely culprit but all the other things that Howard mentioned are also distinct possibilities.

That happened to me once in my 1952 Henney-Packard but in this case it was a fault in the overdrive which is supposed to cut off the distributor just momentarily when pressing the pedal to the floor to pass. It was cutting it off for as long as the pedal was pressing the kick-down switch rather than for a fraction of a crank revolution as it was supposed to do, then blowing up all the fuel at once that was getting pulled in by the engine still turning when I let up on the pedal. The nearly new muffler's seam blew open from one end to the other!

I experienced the backfire and resultant blown muffler once with an in-line 8 and the cause was traced to a sloppily-fitting distributor rotor.

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I've never had this happen with any of my Packards. Never ever had a distributor go out regardless of miles. But I did have this exact same condition take place with one of my Continentals. With a brand-new exhaust system that had been on the car for several months. Of course there was no connection to the exhaust but all the same symptoms.

One day the car started bucking and quit. Had a helluva time getting it re-started. Next few times after sitting, I'd have to put gas in the carb to prime and get the car to start.

Turned out that the carb I had rebuilt for me by a shop was done incorrectly. Floats were occasionally sticking down and flooding the engine with gas (usually at times like on the highway where you barely notice). POW! Backfired. OR the floats were sticking in the UP position, starving the engine from getting gas.

Between the bad carb rebuild and me adding gas to prime for starts after long sits, there was an apparent accumulation in the resonators. Last time I tried this method, Ka-POW! again... only this time it blew the resonators OFF of the pipes!

Yanked the carb-as I should have done much earlier. Danged new one was expensive, but it corrected my problem. No more backfires, no more bucking and exhaust is fine.

While your Four Hundred MAY be having electrical issues. You may want to check the carb.

ALSO I recall someone I knew many years ago having a similar bucking, backfiring issue with a V-8 Packard. Turned out to be the ignition switch and related wiring. So? You'll want to check that too.

Ok Guys thank you so much for all the information. I am going to start small. I just replaced the coil with a aftermarket hotter coil I had with my parts and going to see what happens.
I warmed the car up and took it out for a ride here on the back roads seemed to be ok but this seems to come out of nowhere. Later today will take it on the highway. I do have a spare ignition switch. How do you switch where you put the key
in so it will work with my key? Thanks Again Gary

You can make your own key.

The parts book has how you take cylinder out. The one in the car not a problem

The other need to make a dummy key. Or take to a locksmith.

I had the same missing and backfiring problem with my 1955 Clipper Super. One backfire blew out the muffler. The problem was the distributor terminal insulator was cracked and allowed the terminal to ground against the distributor body causing the misses and backfires. I had been working on the distributor and must have over tightened the terminal nut which cracked the insulator. I replaced the insulator block and all was well again. It had the Autolite distributor, maybe the Delco is similar. Here are photos of the culprit. Hope your problem is as minor as mine was. Good luck.

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Hello again. Thanks for the information on the distributor terminal insulator mine is fine.

I did check about fuel delivery. I have a inline fuel filter
from the tank going to the carburetor. It was old filled with
sediment from the tank really bad worst I have ever seen.
I just put a new one in.....

Could this have been my problem????

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Yes, this very well could be your problem. Like my Continental, your engine might have been going through a series of running rich/starving for gas cycles. Thus the backfires.

With rusty sediment this bad in your inline filter you'll also want to check your carburetor inlet and float bowls.

Frankly at this point, I would very, very strongly recommend that you yank your tank and have it boiled out (at the very least) and sealed. Otherwise with rust this bad, you're only a moment away from more problems. I would also have the fuel line purged from rear attachment to front. Undoubtedly there has to be more crud in the line if this much is in the filter. And be sure to run a ream through the fuel line in the tank. The elbow on the pickup tube inside the tank is the critical point for clogging. Even when the tank appears clean, this little tube can be full of rust and debris.