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‘46 P15 questions from a young new owner


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Hello all! I have recently acquired a 1946 Plymouth P15 ( at least I’m nearly certain it’s a ‘46 based on the SN) I know for a fact the car ran 2 years ago but not since due to a battery issue. Now it’s in my possession and it won’t start. I’ve replaced the battery, bled the oil and fuel lines and reprimed the lines. I’ve tore apart the carb once (just the top side to check if it was actually getting fuel which it was). The starter engages and everything rotates as it should. But still she won’t come to life. I’ve also replaced the spark plugs and from what I can tell they’re firing properly. I’m not sure what I’m missing at this point. She cranks and cranks but no start. Any advice you fine folk could give would be much appreciated but please break it down like I’m a 5 year old. This is my first full project besides minor body work and oil changes etc. I do have a Plymouth service manual but there is so much data there I don’t even know where to start. Pics for attention. 




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The engine needs three things to run.


A spark, delivered at the proper time and of sufficient strength.  This can be checked here's a video on how to check the setting on a non-running engine with nothing more than a timing light. 


Fuel, your carb has fuel in it, but is it making it into the intake?  Not uncommon for a carb to get gummed up from evaporating fuel if it has sat for a long time.  Pull the air cleaner and work the throttle linkage by hand ans see if any fuel is squirting in the carb throat, you may have to open the choke butterfly to see this.


Air, a plugged up air filter might be a remote possibility.  Over filled with oil?  When it's off for the fuel check and if the fuel check passes see if it'll start, or at least try, with the oil bath filter off.




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It is still 6v so that's good to know.  The cables look proper sized, but 6v systems are fussy about current flow. The short cable from the battery to the solenoid is the primary connection for all your car's electric circuits.  Loosen the nut take them off the terminal and clean everything up, put it back together and tighten the not nice and snug but don't over tighten..  D you have one of those simple circuit tester shown in the attached video?  If not get one.  You can use it to make sure you are getting power to the coil with IGN on.   Then make yourself a jumper wire.  Get a couple insulated alligator clips and attach them to each end of a 6 foot length of 12 gauge wire.  If you want you can add an inline fuse holder with a 20 amp fuse.  You can use this to power stuff directly from the battery to see if it works or you can hook it directly to the coil if you suspect your IGN switch isn't passing current.  The clips will let you shut the ing circuit of by disconnecting from the battery.  Before you try to start it you might want to run a compression test on all cylinders as these engines tend to get sticky valves from sitting in storage.


Note. Some compression testers have over long threads where they screw into the spark plug holes so note how far you can screw it in by comparing the thread length of the plug.  While you have the plugs out put some penetrating oil down the spark plug holes..  a real good penetrating lube is a 50 50 mix of auto trans fluid and acetone.  Cheaper too. In the long run.  Don't rush the process, yes it's exciting to get one of these old chunks of Ron to breathagain but patience, and good troubleshooting procedure is a good thing.  Get on eBay and get a shop manual repops are 25 bucks and worth it.  Then go to your library resource section, find the  "Motors Manual" and read and make copies of the trouble shooting guide in the bóok.  Don't grab a bunch of tools and start shotgunning stuff.  There are procedures which will save you time and money and keep you from turning a no start fault into a basket case, with a pile of receipts and empty parts boxes you probably don't need.  The process will also give you an understanding of the systems and how they work together.


It really is as simple as suck, squeeze, bang, blow.


There is also lots of tune up specs, techtips and how too on this sight,.  Go to resources and down loads.  Read read read.  And first part to buy AC or Autolite spark plugs.  The standard plug in AC is 45r. Autolite is 306 I think but the ac number will cross over..  get some masking tape and label the spark plug wires, commit the cylinder firing order to memory.


Welcome and good luck.  The other thing to do is to look at the engine number.  It is on the block stamped into a flat spot above the generator.  Should start with P 15, but engine changes were pretty common back in the day to keep these on the road.  So you results may very.



Edited by greg g
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I can't add much to the excellent advice already given, so...welcome.  If it didn't run before due to a "battery issue", that may narrow down where to look, since it usually isn't a battery issue.  The checks already noted will help clear that up.  We have scads of veterans on the Forum (there's an old thread under "Off Topic" wherein folks discuss their service, gets resurrected every Veterans' Day), but not very many active duty personnel.  I assume because it can be difficult undertaking an old car project when you PCS every other year or so.  We're here to help!  

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I know Greg already said it, but it's worth repeating. I can't imagine getting by without 1) the shop manual 2) a Motors manual that covers the year of my car and 3) the parts manual. Gotta have 'em. All pretty cheap, on ebay. The parts manual will tell you what the name of every bit on your car is, so you can ask questions, and is fantastic for the times you take something apart, walk away for 3 days, and then have no idea how it goes back together. It has highly detailed exploded illustrations of nearly everything. Later on, a Hollander's part interchange book is good to have, for ebay parts hunting. 


I don't know how young you are, but until I was 16 or so, I broke more stuff than I fixed. Looking at a car's insides was overwhelming, until I learned to break it down into systems, and learned what each system did. The chapter sections in Motors does that nicely---carburetion, ignition, generator, starter, distributor, etc. The very first chapter on tune-up will teach you plenty. 


These service bulletin pamphlets are fantastic, some even have a filmstrip (caveman era learning tool) you can watch  http://www.imperialclub.com/Repair/Lit/Master/index.htm  Skip the real specific ones, and go right to general topics like carburetion, distributor, electric systems, etc. 


Finally, you might get something out of watching any of the "Will It Run" videos on coldwarmotors youtube channel. Stoned Canadians take cars that have been sitting for 50 or 60 years, and make them run, dealing with many of the same issues you are right now. One of the videos is a '40-ish Plymouth. 



Edited by ratbailey
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