Starter engages unexpectedly when throttle is depressed when running

[trp3141592]

Hi,

I don't drive the '37 Monster often, but my partner and his son drive it often. Junior reported to me that when the engine is running and he pushes the gas pedal down past a certain point, the starter engages. Nasty noise, not to mention possible starter or flywheel damage.

My first thought is that the vacuum-controlled starter relay switch that is attached to the throttle linkage has developed poor vacuum retention (ie, a leak), and that when stepping on the gas with resultant drop in vacuum, the vacuum switch closes and calls for the starter to engage.

Junior is convinced that the problem is in the starter. I disagree. I think it is that vacuum switch. I could not find this switch in Bob's--does anyone know a source?

Opinons?

--Tom

PS: Junior will not be doing any repairs until this is diagnosed, if he knows what's good for him.

Edited August 28, 2013 by trp3141592 (see edit history)

[Marty Roth]

I've noticed that will sometimes happen if I slow for a corner and, with all the torque of the 320ci, decide not to shift out of 3rd gear.

Apparently there is very little vacuum at that instant, and the vacuum switch doesn't realize that the engine is running.

This will not happen if I downshift, at least to 2nd, or even come to a complete stop (Are those stop signs really more than a suggestion?).

If you drive it normally, and not take advantage of the fantastic torque of this engine by lugging it around corners .....

the problem will likely not occur again.

Let Junior know that we know what he is doing (Kidding, of course).

[Dave_B]

I don't think it's the starter either. Isn't there a wire from the generator to the starter switch to signal when the car is running? Maybe a disconnect there somehow?

Dave

[37_Roadmaster_C]

Tom,

The problem is NOT the starter. There are two possibilities: 1) the vacuum switch is bad or 2) the voltage regulator. There might be a possibility it could be the generator also. The basic way the start system works is that the starter is activated when the throttle is pressed AND the engine is not running. The vacuum switch on the manifold is the primary control for this. This switch is activated by the throttle linkage and is locked out by vacuum when the engine is running. The second starter lockout is the voltage regulators 5th terminal. This terminal provides the ground for the starter solonoid when the generator is NOT generating ( motor not running). It was common in later years for the 5 termonal regulator to be replaced with a 3 or 4 terminal unit which might not provide this lockout, I am not sure of this as the newer regulators claim to be replacements with no problems. Others please chime in on this :confused:. The problem with this system is if the generator lockout fails the vacuum switch can allow the starter to engauge as Marty says when the throttle is pressed in a high torque situation, IE: high gear, low speed acceleration or any situation with lots of throttle. With lots of throttle there is very little manafold vacuum. A solution to this, although not stock, is to add a starter button and abandon the throttle start. This is what has been done to my 37 80C. Now I will admit that I will be restoring the throttle start to mine very soon as I am a big fan of origional design, but dammaging the starter or flywheel is a big concern... Do something to protect the starter and flywheel (add a temporary switch) until the problem is repaired. I will check the wiring diagram for more specific details......

Edit: There is mention of being able to adjust the accelerator switch (vacuum switch assembly) for proper operation. I do not have my service manual here right now so I will look this up later and post what I find about adjustment. I also found a reference to using a 3 terminal replacement voltage regulator and by doing this it eliminates the generator lockout safety and warns that the accelerator switch MUST be in proper working order and adjusted properly :mad:

Edited August 29, 2013 by 37_Roadmaster_C
add information (see edit history)

[Marty Roth]

Robin's point of bypassing the vacuum control for the starter is certainly valid, preferably as a temporary measure.

I have a button wired onto one of the Buicks I maintain. This is not in place of, but in addition to the normal method as an option to engage the starter without flooring the accelerator. This would also function in the event that the standard system were to fail for any reason. That car is a "Driver", and not a show car.

[trp3141592]

Hi,

Thank y'all for the input. Partner, Junior, and I are going to install a push button starter switch and bypass the throttle linkage vacuum switch. That looks like the cure, although it's not original.

Now here's another question. Somewhere along the line one of us has gained weight (AHEM!), and it's a tight fit behind the wheel. The seat absolutely will not move, either forward or backward, so some maintenance (or persuasion) is needed on the adjuster mechanism, whatever and wherever it is. So the question is, how do we get the seat out of the Monster (Sedan)? Popping the butt-cushion doesn't show anything promising. Surely the seat was installed easily on the assembly line where minutes cost dollars. How is it put together? What's the trick to getting it out?

--Tom

[Daves1940Buick56S]

So this thread got me to thinking - always dangerous and expensive! I can see that a lockout on the vac start switch would be desirable but no doubt that was dropped due to cost reasons. So I came up with a design based on the principle that the system voltage is always much higher when running due to the gen output (which is what the original lockout was based on). My design uses a voltage comparator against a fixed reference. I can vary the ref depending on what I find during initial test. Anyhow, the comparator drives a NPN2222 which drives a 5V relay. One of the wires going to the vac switch is controlled by the relay. I think I can do it with all Radio Shack parts. I will do a prototype and let you know the results.

Cheers, Dave

[37_Roadmaster_C]

Tom,

Sorry for the delay in getting to the shop manual..... Anyway, there is a very detailed procedure with diagrams of how to adjust the throttle switch. The switch is actually quite complex as it has a clutch assembly in it that disengages when there is vacuum and requires the throttle to be returned to idle to reset for the next starting attempt. The procedure is more complex than I can reasonably post here. If you can get a shop manual it would be a great investment, about $30.00 on Ebay etc... If you would like, I can scan the pages in my manual and email them to you. Let me know if I can help.

R.

[1937 Buick 66C]

Good Evening Everyone,

A couple of items regarding the throttle start override that I believe might be helpful here.

For 1937 both the +6V and the ground side of the starter solenoid are switched. The +6V side is controlled by the vacuum switch in the intake manifold, the ground is controlled by a relay built into the 5-pole voltage regulator.

The intent was to enable the throttle start capability, and have double protection to prevent the starter from engaging unintentionally. Unfortunately, both the component quality and the design leave a lot to be desired. Here, in Colorado, you never see a Buick of this vintage that has not had a manual starter button installed due to the starter engaging unintentionally under a combination of low speed, heavy throttle load and high altitude (like when climbing a pass). An elderly old-time mechanic neighbor warned be about this as soon as I mentioned that I wanted to re-enable the throttle start capability during my restoration.

The 5-pole voltage regulators have an additional relay in them which is actuated when the generator begins producing current. This interrupts the ground circuit to the starter, so in theory the starter cannot get ground if the generator is "charging". Unfortunately, these 5-pole regulators were really awful and expensive to replace, therefore most have typically been replaced by more traditional 3 or 4 pole regulators. When this replacement is done (there are instructions for how to retro-fit a 3-pole regulator in my 1940 Motor's Service Book) functionality which was provided by the relay is lost. Now, the only protection against the starter engaging while the engine is running is the vacuum switch on the manifold. Under high-throttle, low RPM conditions there is insufficient vacuum in the intake manifold to hold the contacts open, and the starter engages.

When I was doing my restoration, I was never able to locate an operating 5-pole regulator, so I am running a large 3-pole unit (very similar cosmetically). Because I both drive and show my Century, I designed a small box which enables me to demonstrate the throttle start capability when requested, but disable it in favor of a small starter button when driving it on a routine basis.

Please note that the vacuum switches manufactured by Delco are unique for each engine, although they look identical. The throttle linkage connection to the switch differs, and the rotational direction of the switch is dictated by which side of the switch the linkage is attached. The large series Buick and 1937 Pontiac use the same switch, Delco #1607. If you no longer have the correct Stromberg carburetor, or if you have one of the late 1937 cars with a Marvel carburetor, this may not be the appropriate vacuum switch. There are detailed instructions in the factory service manual on how to orient the switch in the intake manifold, then how to adjust the throttle linkage between the carburetor and switch. There is also an exploded diagram of the switch internals - it's really quite complex, and it contains a diaphragm which will eventually fail. I have no idea what would be involved with rebuilding one of these switches, but I'm certain it would not be trivial.

If anyone is interested is lots of additional detail on the throttle start system, voltage regulators, vacuum switches etc, I have lots of images and some additional documentation. Since I don't get on the forum regularly, please contact me directly: kanas<at>qadas.com