1940 La Salle hesitating / misfiring / nearly stalling when warm

[John Barry [CLC17027]]

On a warm day like today in the mid-Atlantic (morning temperature ~70°F; afternoon ~87°F), after driving approximately 25 miles (mixed interstate and state / county roads), my '40 tries to quit when I attempt to accelerate from a full stop:

• Step on the gas and the engine may try to quit altogether
• The auxiliary (electric) fuel pump is of some help, but not consistently
• A very slow and gentle attempt at acceleration (significantly more so than normal) may somewhat avoid the problem
• While standing and idling, instead of a smooth engine sound, there will be an irregular putt-putt
• Don't know whether or not this figures into it but it's difficult to start when cold (taking multiple tries)
• When hot, it has to cool off or it won't re-start

The inconsistent help from the auxiliary fuel pump suggests it isn't a fuel supply problem.  Given the sounds and given that it only occurs after operation, I'm wondering if it's ignition-related, starting with the coil (don't recall when it was last replaced), and working out from there to the distributor/points, spark plug wires, and plugs themselves.

Looking for feedback, etc.  Thanks.

[CarsandDrums68]

I just recently had a very similar problem with my 68 deville. My problem was a mix between the carb and the coil. it would stutter and falter and sometimes giving gas wouldnt help at all. I replaced the coil back to the orginal one, and it runs solid now. I think the coil might be having intermittent problems.

-Al

[John Barry [CLC17027]]

That's a place to start, and a reasonably simple fix at that.  Thanks.

[Bobby B]

Check your condenser and/or points also....Put a dwell meter on it to see what's going on. Condensers start to break up once it gets heated up in there, and they can be intermittent.
                                                                    Bobby

[John Barry [CLC17027]]

Really stupid question: I thought the coil and condenser were one and the same, just different terms.  Apparently not?

[Jon S]

Condenser is in the distributor; coil is outside and feeds the center lobe of the distributor.

Condenser absorbs arcs to prevent point pitting.

[gary griffin]

Often when an engine fails to accelerate when given full throttle the accelerator pump in the carburetor is worn out, or the floats need adjusting. I would look in the carburetor first if there are no other symptoms!

[Steve Passmore]

I agree with Gary. I have seen this many times. Without your accelerator pump working you have to 'Feather' the throttle very slowly to get the car to pull away on just its idle jets. Fast use of the peddle and it will just cut out.
Take off your air cleaner and with a torch look down into the carb and open the throttle linkage. You should see two strong jets of fuel from the accelerator nozzles.   If not, then its the carb.

[Bobby B]

Take off your air cleaner and with a torch look down into the carb.....

Steve,
  Great Advice.......
P.S.... Across the pond here it's a "Flashlight". A Torch might ignite the vehicle or at the very least, singe his eyebrows 
                                                                                                                                                    Bobby

[Steve Passmore]

Wow, that could be nasty Bobby, thanks for correcting that.     I try to modify the English language  to suit you guys when I post but there's always something slips through the net    You know what they say, We are separated by a common language.  Good job we have the same love of Cadillacs.

[Jeff Rosansky CLC #28373]

If the accelerator pump is working then explore the condensor option stated above. When they start to go they mimic fuel issues. You may have spark which will fool you into thinking it is ok.
Jeff

[John Barry [CLC17027]]

Wow, that could be nasty Bobby, thanks for correcting that.     I try to modify the English language  to suit you guys when I post but there's always something slips through the net    You know what they say, We are separated by a common language.  Good job we have the same love of Cadillacs.

Not to worry: I understand our British cousins quite well, having had a couple of British bosses and professors in days gone by. 

By the way, the original advice has to be accomplished with the engine running, I'm sure.

[Bobby B]

Wow, that could be nasty Bobby, thanks for correcting that.     I try to modify the English language  to suit you guys when I post but there's always something slips through the net    You know what they say, We are separated by a common language.  Good job we have the same love of Cadillacs.

Steve,
Wing, Bonnet, and Boot have been a part of my vocabulary for years. Whitworth, Spanner, and King Dick too....    I've had a few dozen British Cars  ............
                                                                                                                                        Bobby

[gary griffin]

To clarify the accelerator pump issue the easiest way is to run the engine at an idle then shut it off and use a flashlight to look down the carburetor while actuating the throttle linkage quickly. If you do not see gas spurting into the throat of the carburetor it is either accelerator pump or float adjustment assuming the fuel pump is providing enough fuel for higher performance levels such a cruising at high speed.