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Electrical question 1940 Cadillac LaSalle

Started by MitchHodge, September 06, 2015, 09:59:14 AM

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MitchHodge

1940 LaSalle, new correct rebuild of starter (starter was double checked and is good), new wiring, everything connected properly, new optima 6 volt battery, does not seem to get much ''kick'' when trying to start car.
Battery was tested perfect, new.
For fun used a 8 volt battery and car turned over, started without issues.

Thoughts?

gary griffin

It's probably time to take apart  your grounds and clean them and probably add a couple.  Insufficient and corroded grounds are often the problem here.  Especially a good ground from the body to the engine block. 
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver

JoeCeretti

The fact that it turns well with 8 volts also tells me it is a wiring issue. At each corroded connection the resistance causes a voltage drop, eventually getting too low to turn the starter. 8 volts has a starting voltage a bit higher and the corresponding voltage drop at each spot still leaves enough voltage at the end point.

So basically what Gary said.  ;D
1938 60S nearly done and then destroyed by fire :(
1989 Buick Riviera (Arctic White Paint / Blue Cloth Interior)

Jeff Hansen

Make sure your battery cables are the proper size.  They should be approximately the size of 00 welding cable - nice and thick - NOT the same size you find on your modern car.

Also consider running an additional ground cable from the battery to either the starter end frame or the engine itself (a starter mounting bolt or a bell housing bolt).

Lastly, the one grounding point many overlook is the connection between the starter and starter solenoid.  Everybody takes the time to clean and paint these items, but there is a physical connection between the two where they bolt together.  Make sure the paint is scraped away on the mating surfaces.

Hope this is helpful to you.  Let us know how your progress.

Jeff
Jeff Hansen
1941 6019S Sixty Special
1942 7533 Imperial Sedan

Jay Friedman

I agree with everything said about grounding, cable size etc.  Jeff's suggestion "also consider running an additional ground cable from the battery to ... the starter end frame...." is a good one, which usually gives good results.  Email me privately at jaysfriedman@yahoo.com and I'll send you an article on how to easily do it.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."

Tito Sobrinho

Look at the condition of your battery. Six months ago, I bought a new 6 Volts Interstate battery. At the terminals, was indeed a 6 Volts but it was 25% charged.
Charged to 100% and the "cranking" was perfect. The battery vendors forget that our electrical system is using the slow charging dynamo and not an alternator.
Since I don't drive much my car, I charged its  battery once a month using the NOCO genius of 3.5A that tells me when connected, the charge level.
Tito S.

1949 CCP 6267X  (First Series)

Thanks to Frank Hershey for its design and thanks to Harry Barr, Ed Cole, John Gordon and Byron Ellis for its engine.

Glen

#6
Was the starter painted when it was rebuilt?  If so make sure the ground path from the end plate to the engine block is good.  The ground brushes inside are grounded to the end frame.  The end frame needs to be electrically connected to the case and the case needs to be connected to the nose and it is in turn connected to the engine block.  If the edges of the case are painted the connections to the end plate and nose is not there.  The end plate is then grounded only by the long bolts that run through starter.  But the cross section of those bolts are not enough to carry the current for the starter. 
Glen Houlton CLC #727 
CLCMRC benefactor #104

MitchHodge

Tremendous thoughts, thank you, will report back later this week

Thank you again for all these tips!

John Barry [CLC17027]

As a general thought, what about an electrically conductive paste applied between static surfaces to ensure better contact?
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Tom Boehm

After I scrape the paint off to ensure good contact on grounds, I put dielectric grease on the bare spot to prevent rust. It is sold at auto parts stores to moisture proof plug connections.