1940 LaSalle Series 52. Knob is under the dash, doesn't twist or turn, just a spring loaded push-pull. It "appears" to have a metal tube connected to the back that runs to the bottom of he fuel pump.
The headlight knob is to the right, wipers are up on top of the dash. (it's the one to the left of the big glare).
My first thought is choke?
Not if it's spring loaded and won't lock, I wouldn't think. Given that it runs to the pump - some sort of priming mechanism?
In reply to Keith Tanner :
Agreed..."L' stands for lift gas up.
No idea but it sure looks like they didn't want just anybody messing with it.
Knob, eh?
I dunno, but I bet it's in here somewhere:
GM Heritage info on the 1940 LaSalle
There is a very clear picture on page 144 of the knob I think you're talking about.
Could it possibly drain the fuel bowl?
Appleseed said:Knob, eh?
I read that in Doug McKenzie's voice.
I'd assume it manually pumps the fuel pump to prime the carb. It's definitely stock as it shows on others
https://bringatrailer.com/listing/1940-lasalle-40-5219/
I'm pretty sure Steve is correct. When these cars sit, the fuel will evaporate out of the float bowl. Having a primer would help on hard starts.
Also, and this is a long shot. Maybe, just maybe the one marked "L" is for lights.
Thanks guys. The knob is a momentary switch, pushes up or down but always returns to center. The line to the fuel pump because that's where the vacuum comes from.
I went to a LaSalle-Cadillac forum and they say it raises and lowers the radio antennae. What Engineer sat down and did all this because raising the radio antennae is such a PITA?
In reply to 914Driver :
So the antenna is vacuum powered. I suppose using that method was a similar decision to how some older cars used vacuum to operate power windows or door locks, it was the technology available at the time.
The knob isn't explicitly shown but power antenna function is described in the factory accessory brochure that's shown on the Old Car Manual Project Brochure Collection website: https://oldcarbrochures.org/United%20States/Cadillac/1940_Cadillac_-_LaSalle/index.html There are also several other useful LaSalle brochures posted there, the Data Book looks especially useful.
The knob's function is most likely covered in the original factory owner's manual - if I were you I'd try to find one of those. The factory shop repair manual and parts catalog are also invaluable resources. It's been a while since I looked but there are a number of vendors who sell factory literature, either online or at major swap meets.
In reply to 914Driver :
That's pretty odd, but bad ass too. I love E36 M3 like that. Made sense to someone at the time.
Oh, that's wild. My '66 Cadillac has a bunch of pneumatic features, but not a vacuum powered antenna.
The power door locks and power rear vent in my wife's '70 Continental are vacuum operated.
Older convertibles like Hudsons have hydraulic power windows, fed by the convertible top pump.
My friend had a 40's Lincoln and the seats were hydraulic. Driving at 70 mph, a seal broke and the seat slammed up to the steering wheel. He said it was a very long 10 seconds to get off the highway.
So if I'm going up a hill in the rain, wipers on, and decide to raise the antennae the engine stalls? Bwahahahahaaaa..
My dad loves to tell the tale of hammering round in his old Ford Popular with vacuum windscreen wipers. The nature of crankcase vacuum being that it is at it's highest effect when deceleration, and goes basically to zero when you mat the pedal, it apparently made overtaking in the rain a high commitment affair....
In reply to travellering :
IIRC the Lotus Elan originally used vacuum to raise the headlights with a similar result when driving hard at night. They changed to using vacuum to lower the lights instead.
Vacuum powered accessories are common up into the 70s. Corvette ditched the vacuum operated wiper cowl door in 73 and maintained vacuum operated headlight lift/ close that included vacuum relays until 1980. Like travellering's dad I had the misfortune of owning a Ford with vacuum wipers. In my case a 1960 falcon squire wagon with the base 170 cid straight six. Wiper action at steady state 50 mph cruise was barely adequate for a light mist. One car I don't miss! The falcon squirrel was its non affectionate name.
In reply to travellering :
Usually, cars with vacuum wipers have a double-acting fuel pump. The second diaphragm provides vacuum to run the wipers and is plumbed in the circuit along with manifold vacuum.
Along the way, they often get replaced with a cheaper, single-acting pump and the wipers just run off of manifold vacuum which does exactly what you described.
My '89 Jeep Comanche (a horrible truck) had vacuum controls for the HVAC. On a long hill, defog would change itself to floor heat and then change back when you got off the throttle.
In reply to ShawnG : Thay very well may have been the case with the falcon. My 17yo motorcycle focused self wouldn't have had a clue at that point. I did make sure the the next car I bought had electric wipers...lol
Vacuum stuck around for a long time in HVAC controls, my 98 Ram has vacuum lines running into the cab for HVAC.
The early C3 vettes used vacuum for HVAC, headlights (up to 82 I think) and the wiper door.
I loved my old VW bugs. Always thought the pneumatic windshield washer was unique. It was a canister that connected to the spare tire and was activated by the air pressure in the spare.
Dont use it too much... your spare may be flat when you need it! 😂
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