Rough starting, decent running- '30 Plymouth

[hursst]

Hello,

   A few months ago, I was driving my 1930 Plymouth Roadster and it suddenly had no power, then the engine stopped within another 2 minutes or so.  Long story and a tow later, it was the points and condenser.

 

   I replaced the points and condenser and it started right up again.  However, it never quite ran the same in terms of starting up.  Over the last few months, it has gotten harder and harder to start, but always will start.  When it does start, there's some gray/blue smoke, and it will run very rough, it will just barely run.  Given about 2-3 minutes, after it warms up, it will settle down and it will run fairly well.  The smoke goes away and it smooths out and gives a decent ride.  I can drive it around, little to no smoke, full power.  Another issue is that it misses quite frequently at idle.  It would always miss a little, but it is much worse since I replaced the points and condenser.

 

   Since this problem started, I replaced the 4 plugs and adjusted the timing 3 times.  I'm an amateur mechanic at best, so I'm assuming I got it right, I followed the exact procedures of the owners manual.

 

   Any ideas on what may be causing the hard starting?  The only thing I can think of is that it may need a valve adjustment.  It's been about 900 miles and 5 years since the last valve adjustment.  As you can expect, when I drive it, I usually go no more than 10 miles or so, as I'm afraid it will leave me stranded.  The owner's manual didn't have an exact time frame for valve adjustments.

 

   Thanks for any thoughts!

 

-Chris

[keiser31]

Just a thought....it's common to get a bunk condenser these days.

[Guest]

1 hour ago, keiser31 said:

.it's common to get a bunk condenser these days.

Back in the 60's one of the tune up men in the dealership where I worked would not replace a condenser routinely with a tune up as he/we found about a 10% failure rate on new condensers.  These were genuine right from GM Delco condensers.  Today it is much worse.

 

As to your problem.  If it were me I would do a dry and wet compression test followed by  running the engine while connected to a vacuum gauge. 

Your problem could be high resistance in the ignition system.  Solution would be to undo  and clean every connection.

It could be as simple as a weak diaphragm in your fuel pump if it hasn't been replaced with an ethanol resistant one.

It is possible that you have sticking valves.  IMHO a ten mile drive does the engine no good at all.  Perhaps ten miles in second gear faster than 30 mph may help but without information from the tests the only possible solution is another condenser and some serious running.  In over 60 years, touring with old cars, the ones that were only driven occasionally and only short distances were the ones that broke down enroute.  It didn't matter if they were completely restored or just had ordinary maintenance.  Without any checking or preparation I have started out on 400+ mile trips with my daily driver and have only broken down once and that was my fault not the cars.

Good luck with hunting down and fixing your problem.

[PFitz]

Condenser quality is still poor. For many years now, I always buy more than one at a time. Got tired of wasting time having to run back to the parts store to swap a DOA condenser while trying to finish a tuneup. At least with more than one I have a better chance of finishing the tuneup and the DOA ones can get swapped next trip to the parts store. If none of the extras are DOA, then all the better.

 

Paul

[hursst]

Thanks for all the tips.  I'll start with a new condenser.  The one I bought was an NOS one, I figured I'd have better luck with something 70-80 years old than some chinese piece of garbage.  If that doesn't help, I'll move on to some of those other tests.  

 

Thanks!

-Chris

[DFeeney]

Hello.  I also have a early Plymouth 4 .  The distributor points and condenser ground out through the distributor body.  The body is loose in the block so it can rotate when you change your manual spark advance.  It is not necessarily a good ground.  My distributor body had a extra threaded hole on it and I added a ground wire from the distributor body to the engine block.  This should allow for a consistent ground.  The carb is a updraft with out a real accelerator pump like the mid 30's carbs had.   See if it starts better with a squirt of either. I run a later BB1 carb on mine like they used on the COE Chevy trucks.

[hursst]

I'll try this as well, but the main problem is the extremely rough running right after start up.  It will always start, it usually takes 5-6 attempts, but it will start.  Before I replaced the points and condenser, it would start easily and run just fine from the get-go.

[keithb7]

From here, not knowing anything about the car's history, I'd want to dig in and learn about the condition of several parts. Points, cap, rotor, coil, wires, condenser and surrounding wires & grounds, compression Wet/Dry, valve set, valve seat seal-ability, timing, vacuum and centrifugal advance, dwell, fuel pressure, float height, accelerator pump, choke operation, exhaust diverter valve operation,  spark plugs, clean carb and bowl...That should nail a few things down. Some key test results that you find along the way will determine your next course of action, or not. 

 

The list seems long, but not knowing any history of the car, that's what I'd tackle.

Edited August 25, 2020 by keithb7 (see edit history)

[trini]

Tinindian, you made some good points here. . Test your condenser for leaks. Ground the body to one end of the battery post and the lead to  the other post. Use a test light to check for leak on  the body. The test light will glow if there is a leak. Use a test light to check for leaks at the points. They could be bouncing on fast speed.. How old is the coil ? Check it on the bench. Try a new coil. The hard starting could be flooding  fuel Reason for black smoke.

 

Cheers.

Harry in Thornhill. 

[hursst]

Thanks again.  I'll try some of these tests this weekend.

[hursst]

I examined the various parts of the ignition to start with and started to get into the connections around the distributor and I found that thin ground wire from the coil to the distributor base was attached to the post on the distributor base at a sharp angle.  Upon further examination, it was twisted a little when it was last installed, which, I guess, eventually allowed some of the wire strands to fray.  Maybe the wire has 16 strands in it that are braided to make up the whole wire and 4-5 of these strands were severed.  I cut off the bad end, stripped the now good wire, and re-installed and crimped the connector.  

 

Vast improvement, car started up first crank, still ran a little rough, but about an 80% improvement.  Smoke was reduced by about 90%.  Came to smooth idle faster and ran okay at idle.  I think this was my primary problem.  Engine still misses, runs a little rough until it warms up, but is otherwise average running, but I wouldn't say good.  I think it's about due for valve adjustments, but I think the engine is probably gunked up from 35 years with of mostly shorter-term driving.  I'll keep doing some more tests over time, and when I get time to do so.

 

Thanks again for all the tips and help.  I'll see if I can keep improving the running condition of the car as I keep running some tests.

 

-Chris

[PFitz]

Congrats. Good find.

What rough running it still has may be due to fouled spake plugs caused by the distributor's poor ground causing misfiring. A good long drive may clean them, or if not, then replace them. 

 

Paul