Starter engaging while engine is on

[B.Liesberg]

On my 39 Century, the starter solenoid is engaging while the engine is on and grinding on the starter ring gear. I'm going to check the wiring later to-day to see if it's bad somewhere, but I wanted to ask to see if this is a common problem caused by something else before I go crawling around under the dash.

[Morgan Wright]

Vacuum leak to cut off switch??

[Morgan Wright]

....at least I hope it's a leak, Bob's sells new vacuum starter switches but it's like $200

[B.Liesberg]

It looks like a solenoid, not a pneumatic system.

 

[DonMicheletti]

With the throttle starting, the electrics and vacuum system are linked. It an be either. Solenoid issues are rare, but not unheard of.

[B.Liesberg]

Where does the electrical system and the vacuum system meet?

[1939_Buick]

4 hours ago, B.Liesberg said:

On my 39 Century, the starter solenoid is engaging while the engine is on and grinding on the starter ring gear. I'm going to check the wiring later to-day to see if it's bad somewhere, but I wanted to ask to see if this is a common problem caused by something else before I go crawling around under the dash.

Download the 1942 Buick shop manual. All of it section by section. The pdf link does not work.

http://www.oldcarmanualproject.com/manuals/Buick/1942/Shop Manual/

It is very comprehensive and has information that can be used with all straight 8’s.

It has more information than was included in older “Shop Manuals” before 1942-41

 

There is information on that common fault in the 1942 shop manual.

Does the car start by flooring the accelerator? The carb should have a starting solenoid vacuum switch that goes to the starter. Unless it has been replaced by a manual switch (not uncommon).

Edited December 21, 2018 by 1939_Buick (see edit history)

[B.Liesberg]

There is a button under the dash to start the car.

[Morgan Wright]

22 hours ago, B.Liesberg said:

There is a button under the dash to start the car.

 

The button sends juice to the vacuum switch on the carb, which is closed when the engine is off and your foot is on the gas pedal, and because the switch is closed the juice goes from there to the solenoid. Once the engine starts, vacuum from the carb opens the vacuum switch so the starter solenoid doesn't get any juice. Look around the carb or for a weird thing that you can't figure out what it is, that has wires on it. That's the vacuum starter switch.

 

http://www.oldcarmanualproject.com/manuals/Buick/1942/Shop Manual/13 Electrical System/image11.html

 

http://www.oldcarmanualproject.com/manuals/Buick/1942/Shop Manual/13 Electrical System/image12.html

.

 

Edited December 22, 2018 by Morgan Wright (see edit history)

[B.Liesberg]

There is nothing on the carb with wires sticking out. There was an open spot on the passenger side of the carb that looked like there was supposed to be something there at one point... I put a metal cover over it because there was a slight vacuum leak through it.

[Morgan Wright]

Bob's sells them. Bobsautomobilia.com but the online catalogue stinks. You should get the print catalogue or call them. They want $120 plus $60 for the core but you don't have the core.

 

 

[Morgan Wright]

I might have an extra one. Let me look tomorrow

[B.Liesberg]

I don't really have any issues with not having this part, if anything it seems superfluous. I just wanted to check and see if there were any known problems with the solenoid before I get too deep into it. I'll try and diagnose some wiring problems and see if I have an issue somewhere.

[MCHinson]

Assuming the 1939 is similar to 1937 and 1938, there are two different controls to prevent the starter from engaging when the engine is running. One is electrical and one is vaccum. If the vaccum system has been bypassed, the electrical one is your only way to prevent that from happening. How is your generator output? If the generator output is too low, it might be what is causing the starter to engage when it should not. 

[Morgan Wright]

Looks like your vacuum system was bypassed. I got nothing.

[Gary W]

Here's a thread started in 2010.  The discussion describes how to install a momentary switch under the dash to eliminate these issues with the vacuum start switch and/or a defective voltage regulator....   maybe worth the read:

 

 

 

[DonMicheletti]

You may have the wrong carb or regulator. The carb would have no wires, just electrical terminals

 

The best place to start is with a service manual where the entire system is described and how it operates.

[B.Liesberg]

I think I found the problem...

 

Most of the wiring is original and a bit brittle. Looks like the oil pressure line popped out of it's clip and started chafing on the wire bundle going to the starter and shorted the switch wires.

[Joseph P. Indusi]

Glad he found the problem.  Since his carburetor start switch has been removed and replaced by a push button switch the starter could not activate even with engine at low rpm or low output voltage of the generator.   The driver would have to push the starter button to activate the starter under any conditions.  I am not surprised that he found faulty wiring as the cause.  

 

Joe

[Bruce W Jones]

New to these type starters, just bought a 39 series 40 and I have gas pedal starter system and a button. Both work and not trying to engage like OP had but I hate the whinning noise it makes after car has started. Is this normal and is it possible to mod it to modern starter cylinoid type with key start like late models. Thanks

[MCHinson]

If you have any odd noise after starting, something is wrong. It sounds like the starter drive is sticking and not retracting when the engine starts. I would suggest you try cleaning or replacing the starter drive from your description of the noise. It is also possible you have a wiring problem causing it not to retract. Do you have a factory service manual for your car? 

[Bruce W Jones]

I do, but looks Greek to me. I started it up today with the button without touching the gas and no noise after it started, sounded like conventional late model set up.

[BuicksBuicks]

In my '37 Special it was a simple matter of adjusting the depth of the solenoid plunger. I  had agonized over what damage had been possibly done to my flywheel gear but five minutes was all it took; and there was no flywheel gear damage.

[Bruce W Jones]

At times the starter functions as it should with no noise after engine starts but  most of the time it whines. So this hopefully eliminates elect. Problem or not. Hopefully just sticky starter drive as MCHINSON suggested. Gonna have a mechanic remove and fix next week. Thanks guys

[Bruce W Jones]

Update, removed and took to starter to rebuild shop. Bad solenoid, replaced and works as it should. 

[Jim Nelson]

BTW,   If you have a starter turn on while the engine is running, you are flirting with big $ repairs.    My 248 started that and it went quickly to a point where the starter would not engage the ring gear.    First, finding a new ring gear  is tough.   I found one in Wisc.  $300 big ones.   That gear fits only 34 to 38 flywheels.   The 1939 and newer ring gears won’t work and those are readily available.   This repair requires you to pull the pan, remove the rear main to gain access to the head of the flywheel bolts.   Your SM will guide you.   I ended up doing almost a major overhaul as I checked the conditions inside the engine.   You have to move the rear back enough to pull the trans.  and then clutch and finally the flywheel.   Fix this NOW or you will pay the piper later.   Removing the automatic vacuum starting circuit is the best way.  Disconnect the grounding circuit that goes to the regulator.   Look at your wiring diagram for the wiring diagram.    Add a start button under the dash and know that is the only way you can engage the starter..... If you want looks, leave the parts and wires that go nowhere now.   Treminate them so they can not be hooked up again.