Re: Fails to start warm

Posted by DavidPackard On 2020/7/26 20:08:41

Not an uncommon question paulg3. I'm assuming the engine rotation is very slow when you are attempting a hot restart, and it is the slow cranking speed, plus very low voltage to the ignition system that is the cause of the problem. Twenty minutes later the cranking speed is high enough for the engine to start. If low cranking speed is one of the symptoms, then:

Most will suggest that for a 6 volt car 2/0 battery cables should be used, and all connections should be clean, so step one might be a check of the voltage level being supplied to the starter during this condition. A high voltage points to a secondary voltage drop somewhere in the current path, but a low voltage may point to a current/voltage/temperature characteristic of the battery.

I 'fixed' a similar problem by changing the solenoid, however since that car was equipped with the large format Delco solenoid I also had to remove the starter. There was a good amount of oil and 'crud' between the starter and bellhousing. That area received a good scrubbing before reassembly, so I really don't know if the 'crud' or the solenoid was the problem. Perhaps a 'stout' grounding strap from one of the starter bolts to ground would help. Prior to changing the solenoid I replaced the cables with 2/0 items and cleaned the connections, and the battery was also changed. The take-away from this is; big cables with good connects are mandatory on these cars, and the path to ground includes the solenoid and bellhousing/starter interface.

The second experience is something you don't want to hear. My '48 had exactly the same set of symptoms . . . even down to the time it took to recover. Over about a year I set about, changing the cables, cleaning every connection, changing the solenoid, installing a rebuilt starter (the interface this time had a good amount of Packard gray paint, but otherwise clean, it went back together clean metal), and then finally decided to jump the car just after a shutdown in the middle of the summer (110+F). With the second battery connected the car started readily. All the while I never thought the battery was the culprit because it was the first thing I changed . . . it was one of those modern AGM units that are in a case that looks like the OEM original . . . Willard in this case. I put in a NAPA 3E flooded lead/acid and the car has not had a reoccurrence of the 'hot start' problem.

If the engine cranking speed is 'normal' then I would look down the suggested 'vapor lock' path.

dp