Carter WCFB starter switch issue

[krinkov58]

I have a 1952 Buick 76R with the Carter WCFB...yesterday I had the manifolds off and added a 1/4" phenolic riser under the carb due to some heat soak issues (I have an small exhaust leak).  Didn't really fool with the carb itself other than to put a new paper gasket on the air horn for the air filter.  However, upon reassembly the following happens:  when the ignition is turned on, the charging gauge immediately jumps all the way over to "Discharge" and the wiring harness heats up.  Car obviously does not start.  But when I disconnect the 2 wires from the WCFB's starter switch, everything works perfectly...charging gauge acts normally, no heat in the wiring, car starts as usual when the wires are crossed.  So I am guessing the starter switch on the carb is somehow grounding the hot wire?  Anybody ever heard of this happening?  

[old-tank]

Not knowing if the switch on your '52 WCFB is like the ones on a 55, I will say that unless the switch is broken, there is no way to short internally.  Disassemble the switch (after removing the carb so you can see and test) and check function with an ohm meter.  In 55 (12v) the wires to the switch are not fuse protected and will instantly fry your harness if shorted...this can happen with 6v, but will take longer.

Willie

[Bhigdog]

Prime rule is when you do something and it goes bad, undo what you just did before you do anything else...........Bob

[carbking]

Is it possible adding the spacer causes one of the wires to stretch, allowing a defective area of insulation to touch something it should not touch?

 

Jon.

[krinkov58]

Bob,

 

  Basically all I did electrically was remove the two starter leads, tape the ends and set them aside.  Then re-attach them.  I did check to see if I had stepped on any of the wires for the neutral safety or brake light switches and crossed something while working on the manifolds, but nada.  There's plenty of slack in the leads so 1/4" didn't stretch anything, still plenty of slack.  When the leads are off of the carb and I switch the ignition to "on", everything is kosher...touch the leads together; the relay kicks the solenoid/starter over and the car fires up.  But when the leads are attached to the WCFB's switch, the millisecond the ignition is switched to "on" the gauge flicks hard to "Discharge" and the wiring begins to heat up.  No click from the relay.  Willie, I'm going to disassemble the switch like you said...6V gets pretty hot too and as soon as I saw the needle go to "D" like that I switched the ignition to off and checked the harness...got pretty warm.  Jon I went through some of the wiring but I am going to double check it tomorrow...maybe when I am holding the leads the wires are slack enough not to short somewhere down the line...have you personally ever seen one of the vacuum starter switches short?  

[Paul Falabella]

Regarding the unprotected starter circuit. One of these days I will return my 55 to the carb starter setup(now a push button start). Can/Should a fuse be put in that circuit?

[KAD36]

You may need to connect 1 wire at a time to the carb switch and see which leg of the circuit is causing the short.  Hard to visualize how what you did caused a direct short to ground given the internals of the carb switch but that sure sounds like what is happening.

 

Inside the starter switch is a simple plunger with 2 copper contacts zero ohms impedance that press against the terminal side of the switch where the wires hook up.  Make sure they are not contacting the carb body in any way (if its like the 55s).

 

You could ohm out each switch terminal (where the wires attach) from contact to the block and see if there is a short there before you take it apart.  Sometimes we accidentally fix electrical problems when we disturb the circuits so measure it first before you disassemble the switch.

 

Without knowing the 52 circuit and assuming it is like the 55s, you can also trace the schematic in the shop manual, find the "hot" side (current would go into the switch), only hook that wire up to the switch and leave the other off. See if the discharge still happens.  If so its somewhere either in the switch assembly and shorting out to ground (which could still happen since the studs and nuts will ground the carb to the block) or the wire to the switch got grounded out somehow when you connected it.  If you lifted the carb from the manifold thus electrically isolating it from the block, and hit the ignition and see no and that "fixes" it it would verify where the short is.

 

If you don't get the problem, it suggests the short is in the wire running from the other end of the switch.  Follow that from the switch to where it is terminated and unhook it there, see what happens.

 

Since you can get it to work properly when you physically touch the two wires, my hunch is coincidentally something shorted out to the block or carb base inside the switch or in the wiring it hitting something metal along its path before it gets to the starter relay.

 

 

Paul - yes would advise hooking up a fuse.  Reference link below:

 

http://forums.aaca.org/topic/90213-wiring-short-on-starter-switch-close-call/?hl=%2Bstarter+%2Bswitch+%2Bfuse

 

Your car is looking better and better with all the work you have put into it btw,  Nice job

[old-tank]

Like Ken, I too shorted the wire to the carb switch.  But unlike Ken, I still don't have a fuse there...just never turn on the ignition unless the the wires are connected or taped!  I do have a fuse to the horn relay:  http://forums.aaca.org/topic/251435-electrical/

Willie

[krinkov58]

Issue mysteriously "went away" somehow...and I hate when that happens.  It's sure to return in the future in a parking lot far from home.

[60FlatTop]

We are becoming owners of 50 and 60 year old wiring harnesses with our cars. A few times I have looked at Megohmmeters. Prices are quite reasonable from when I first used them and one I probably should pick one up.

 

They can me used to find failing wire insulation and resistance related electrical problems by putting high, low amperage power, like 500V and measuring leakage. They are down to about $100-$150, about the cost of a flatbed ride. It would be a good test for an intermittent problem as you describe.

 

You might also be able to get an air conditioning or refrigeration mechanic to test it. They used a megger to test windings on hemetic compressors.

Bernie

Edited July 7, 2015 by 60FlatTop (see edit history)

[carbking]

Issue mysteriously "went away" somehow...and I hate when that happens.  It's sure to return in the future in a parking lot far from home.

 

Maybe someone replaced the original switch with one made by Lucas. Lucas did offer a three-position switch (off, on, flicker)

 

Seriously, there might have been a spot of rust allowing the hot wire to "ground", which is now moved or burned up by the current.

 

Take the switch apart, and clean it vigorous. Use a toothbrush (obviously, one you no longer use otherwise ) to clean the plastic components. Inspect the plastic components for cracks. New switches, although not inexpensive, are available; but yours probably will clean up well.

 

If you need a new switch: Buick has used at least 4 different switches. Make sure the vendor can look up the switch by the tag number of your carburetor.

 

As to a possible insulation issue in the wiring harness; not my field. Will leave this possibility to others.

 

Jon.

Edited July 7, 2015 by carbking (see edit history)

[krinkov58]

Bernie and Jon, I'm going through the wiring harness slowly but surely as I'm fixing things...the switch itself could use a cleaning so the next time I have my carb off (should be soon, I have to replace ten manifold studs because they're stripped to death) I'll give 'er a good cleaning.  

 

Someone must have installed one of those switches in my fuel sender circuit as well...replaced the missing float and gasket the other day and now the little needle flickers all over the place!