Starter - Solenoid Diagnosis

[Whippet]

Hi:

Moyer manual doesnt help on this one, so hoping you can point me to the right prior post in forum -- or new advice.

I'd like to know how to diagnose faulty starter - solenoid.

System description is:
1) push-pull ignition switch
2) push button starter switch
3) original 33 year old starter motor

Symptoms are:
1) a few weeks back (last sail) starter wouldnt fire with switch (even though just replaced a few weeks back when i thought symptoms were due to bad switch)
2) when i attached hotwire across terminals in back of starter switch, then starter did kick in -- and switch worked every time thereafter -- almost like i shocked the circuit into life
3) yesterday, no action when hit starter button. and hot-wiring switch didnt work.
4) I believe batteries to be good. Blower motor going full rev -- and battery indicator solid in the green.

Headed back to boat tomorrow. Assuming i give the battery a full charge with shore power and confirm full power, what diagnostics can i do to confirm bad starter or solenoid? Wire right from battery to starter - to rule out ignition circuit?

Thanks gents

[Al Schober]

The solenoid works by pulling a brass disc against the interior ends of the two big lugs on the solenoid. You can short them externally with a screwdriver (disposable?). That should make the starter spin.
Solenoids often go bad/intermittent due to arcing and pitting of the brass disc. This will be apparent by examination after disassembly. I've restored them in the past just by inverting the disc.

[edwardc]

There is a scenario that explains this. It's one I used to see on my Volkswagens.

The coil in the solenoid actually consists of two windings. This is because the magnetic field needed to pull-in the plunger and engage the bendix is much greater than the field needed to hold it in place once actuated. So they use two windings, and arrange things so that one is always energized when starting, while the other is only energized when the plunger is not actuated. One end of each winding is connected to the "S" terminal. The other end of one of them is connected to ground via the housing. It always gets power when +12 is applied to the "S" terminal.

The other end of the other winding is connected internally to the "+" terminal of the starter motor itself. Since the motor windings are such a low resistance compared to the coil windings, most of the 12v is dropped across the coil, generating extra magnetic field, helping to pull-in the plunger.

When the plunger pulls-in, it connects the heavy battery terminal to the "+" side of the motor, causing it to start. But this also connects the other side of the second winding to +12 too. Now, this winding has both sides connected to +12, and it draws no current, effectively dropping out of the circuit. But the remaining winding has enough magnetic field to hold the plunger engaged.

The "no start" problem occurs when some corrosion, wear, or dirt starts to build up on the brush contacts in the starter motor itself. This causes additional resistance, which in turn reduces the current through that second solenoid winding. If the starter just happens to land on one of these "bad" spots after starting, the next time you try, it won't start. Draws current, but no "click" from the plunger.

On the Volkswagen, I used to get out of this by briefly shorting the main battery terminal on the starter to the "S" terminal with a screwdriver. This would bypass all of the starter switch wiring (and its associated resistance) and provide slightly more current to the solenoid. This would be enough to "bump" the starter motor off of the weak spot, which would then allow starting with the key as usual.

So, in summary, I think it's the starter itself.

[Whippet]

Thanks for help

looks like a call to Ken-parts is in order for a rebuilt unit

i suppose after 33 years, it's time

[capnward]

I have a similar problem that seems to be getting worse. Occasionally, but more often now, when I push the starter button nothing happens. If I hold it in for a few seconds, sometimes longer, it will eventually trigger the starter. It's like the electricity takes time to burn through whatever is built up on the brush contacts on the starter motor. The wiring looks ok. Sounds like I may be due for a rebuilt starter; I start my engine several times a day quite often in the summer, and it's probably 15 years since the starter was rebuilt. I have used the screwdriver method in the past as well, to good effect. I have replaced the push button ignition switch when the real problem was probably the starter.

[Mo]

Originally Posted by capnward

I have a similar problem that seems to be getting worse. Occasionally, but more often now, when I push the starter button nothing happens. If I hold it in for a few seconds, sometimes longer, it will eventually trigger the starter. It's like the electricity takes time to burn through whatever is built up on the brush contacts on the starter motor. The wiring looks ok. Sounds like I may be due for a rebuilt starter; I start my engine several times a day quite often in the summer, and it's probably 15 years since the starter was rebuilt. I have used the screwdriver method in the past as well, to good effect. I have replaced the push button ignition switch when the real problem was probably the starter.

Might also be the starter button.

[joe_db]

How I fixed this issue on my boat:
http://www.moyermarine.com/forums/sh...3786#post73786

[edwardc]

Originally Posted by joe_db

How I fixed this issue on my boat:
http://www.moyermarine.com/forums/sh...3786#post73786

This is exactly what I ended up doing on my volkswagen too, using an old horn relay.

[capnward]

I should maybe describe my problem in more detail;
When I push in the starter button, often there is no click, only unnerving silence. If I hold the button in, after 10 seconds or so it starts. So far. When there is a click, the starter always engages and spins the engine. I think this means the solenoid is OK. Between the solenoid and the ammeter, I recently replaced the 30 amp inline fuse and its surrounding 12 gauge wire, with a 30 amp circuit breaker and 10 gauge wire, thinking the wire was too small to transmit enough juice. This didn't solve the problem. I have replaced starter buttons usually about once every two years, but the problem returns after a while. I have ordered yet another starter button, but I suspect the problem is worn starter contacts. I am trying to spend $40 instead of $240, which is the price of a Moyer rebuilt starter. I guess eventually I will have spent $40 six times to save spending $240. The relay idea is intriguing, I will also look into that. I will check the wiring again as well, but it looks good. The ground cable from block to negative battery terminal was new last year, still solidly attached..

[joe_db]

Like I said, this is EXACTLY what mine did. You can check this out by jumping the start terminal to the battery cable. If that starts the boat reliably, you can do my fix or replace the start button and wiring to it.

Originally Posted by capnward

I should maybe describe my problem in more detail;
When I push in the starter button, often there is no click, only unnerving silence. If I hold the button in, after 10 seconds or so it starts. So far. When there is a click, the starter always engages and spins the engine. I think this means the solenoid is OK. Between the solenoid and the ammeter, I recently replaced the 30 amp inline fuse and its surrounding 12 gauge wire, with a 30 amp circuit breaker and 10 gauge wire, thinking the wire was too small to transmit enough juice. This didn't solve the problem. I have replaced starter buttons usually about once every two years, but the problem returns after a while. I have ordered yet another starter button, but I suspect the problem is worn starter contacts. I am trying to spend $40 instead of $240, which is the price of a Moyer rebuilt starter. I guess eventually I will have spent $40 six times to save spending $240. The relay idea is intriguing, I will also look into that. I will check the wiring again as well, but it looks good. The ground cable from block to negative battery terminal was new last year, still solidly attached..

[Whippet]

Originally Posted by Whippet

Thanks for help

looks like a call to Ken-parts is in order for a rebuilt unit

i suppose after 33 years, it's time

I did get the rebuilt starter from MMI. Other than usual tight access on C&C27, two bolts and wiring and jack's your uncle, it was done. Fired right up, so starter must have been the culprit.

I tried to trace wiring so i can understand the functions. One clearly goes to starter, thus the "S" terminal. Can someone explain where the other smaller wire goes and its function? Appeared to head off to the OPSS?

Thanks for help as usual.
Steve

[JOHN COOKSON]

The idea behind the wire from the starter to the OPSS is that the fuel pump will operate while the engine is being cranked before the oil pressure comes up.
It is a factory installed feature of a late model A4.

TRUE GRIT

[ndutton]

Originally Posted by JOHN COOKSON

The idea behind the wire from the starter to the OPSS is that the fuel pump will operate while the engine is being cranked before the oil pressure comes up.

Please be advised on two points regarding the OPSS bypass wire to the solenoid 'R' terminal:

1. If you are not in the habit of running your carburetor dry when you shut down, the bypass is unnecessary for starting. There is sufficient fuel in the carburetor bowl to get the engine started and running at idle for about a minute without any pump operation (the OPSS closes anyway within maybe a second or two of cranking).
2. Facet is not a fan of the OPSS bypass. They feel there's a risk of pump damage from transient voltage spikes from the internal solenoid coil when the start circuit is shut off. That's how our ignition coils work, they build a big charge when energized and dump the entire load when power is removed.

[Stevenph]

This is a little off topic - but i'm new here and can't seem to figure out how to start a new thread...

I have a spare prestolite starter and solenoid that came with my early model A4, and i'm trying to determine what state it's in. When i hook up a battery connection and engage the solenoid with a screwdriver, i get some spark and a continuous whirring sound (from the solenoid), but the motor doesn't turn.

I took the motor apart and though the brushes are worn, they are still making good contact with the spindle.

I'm familiar with the solenoid click in automobiles, but have never heard this whirring sound or know what it means. New to A4's obviously...

Thanks!
Steve

[ndutton]

To start a new thread click on the category under 'Discussion Topics' in which you want it to appear on the main forum page. Once the category opens you'll find a 'New Thread' button on the upper left side. Click that and you're good to go.

As for your starter question, solenoids click, spinning starters whirr. It sounds to me like the starter is spinning fine but not throwing out the pinion to engage the ring gear on the flywheel.

And welcome to the jungle.