bad starter solenoid?

[Formerly Steve Wilkinson]

Once every 50 starts or so, the starter on my '83 SC won't run. Nothing.

If I have a bad starter solenoid, would this allow the starter to motor without engaging the flywheel, or does a bad solenoid prevent the starter from running at all?

I suspect the solenoid because sometimes--not always--the starter will work if I whack the motor with a mallet.

[Joe Bob]

Do you get a click? Or just nothing? Does it do it when hot, cold or both?

You can do the hot start fix, you can pull the solenoid and open it up and check the dielectic grease or simply have it replaced. My vote is new grease or replace the solenoid.

[Formerly Steve Wilkinson]

Only does it when cold. Often, in fact, when the engine warms the starter works again. I frankly can't tell you whether I'm getting a click or not; too many years of flying loud airplanes have affected
my hearing. At least I can't hear any click...

[Joe Bob]

Pull the starter, do the solenoid.....bet the grease looks like cold, black butter. If you have an old fashioned rebuild shop around, have them do the repair. They can also test the windings and give you a warranty.

[IDGAF27]

Solenoid makes starter engage with flywheel. So even being bad(solenoid) you should here starter spinning , I think.

[Formerly Steve Wilkinson]

Hmmm...I would think that a starter solenoid would be rigged so that the starter motor doesn't work _until_ the instant the starter gear is engaged with the flywheel ring gear. Otherwise, you'd be trying to engage a rapidly spinning small gear with the stationary big gear, which doesn't sound like a good idea. So if the solenoid doesn't work, the starter doesn't turn is my theory.

[LM3929]

Check/replace the trans ground strap it can cause the same problem.

Lorne M.

[ischmitz]

The solenoid moves the gear to engage with the starter ring gear AND shorts the +12 Volt to the starter motor. If you get nothing at all (not even the engage click) my guess is either a hairline crack in solder connection of the wires inside the solenoid to the spade connector on the outside. You can easily fix that yourself with a soldering gun. The solenoid comes apart pretty easy and it will be very obvious. Or maybe the spade connector itself is grimy and needs some cleaning.

The other possibility is a bad ignition switch (the electric part) not making contact.

Cheers,
Ingo

[IDGAF27]

Originally Posted by Formerly Steve Wilkinson

Hmmm...I would think that a starter solenoid would be rigged so that the starter motor doesn't work _until_ the instant the starter gear is engaged with the flywheel ring gear. Otherwise, you'd be trying to engage a rapidly spinning small gear with the stationary big gear, which doesn't sound like a good idea. So if the solenoid doesn't work, the starter doesn't turn is my theory.

You right..
I should of typed : " If you jump wire the starter........................."

[Ned, NYNA11]

Stephan,

Ingo is correct regarding the way it all works. Do the following to find out whats wrong.

First, disconnect the wire that connects the solenoid to the ignition switch and rig up a test circuit with a couple of long wires connected to a vom on the passenger seat. Twist the ignition switch 100 times and if the connection is good you will get 12 volts on the vom each time. I once had a loose connection where the loom with the yellow wire from the switch is brought through the firewall via a plug.

Next remove and clean both battery cables. Then do the same for connection strap between the transmission and the frame.

Next step, remove the starter and the battery and test the starter on the floor. Secure the starter before testing it because it will do more than spin.

Next connect the battery + to the big solenoid connection. Connect the frame of the starter to the - battery. Hook another piece of wire to the battery + and just touch the other end to the terminal that is normally connected to the ignition switch.

The starter will spin and the Bendix will fly forward each time you do this.

At this stage you will be getting close. Next you will have to remove the solenoid and have a look.

[ischmitz]

You could also buy one of these remote starter switches. Extremely handy when doing valve adjustments. It has two aligator clips. One goes to the positive terminal on the starter and the other to the spade where the yellow wire attaches. It simulates the start signal. Every time you hit the trigger you should hear the solenoid and the engine will bump over.

MAKE SURE the car is out of gear.

[psalt]

Hello Steve,

The elusive 911 dead starter problem can be hard to solve. You can swap out a lot of parts and still have the problem. You can check all the connections, wires and grounds in the circuit, you can replace the ignition switch and starter and still have the occasional dead "click". The starter solenoid does two jobs, it engages the starter drive and connects the heavy cable to the starter motor. These solenoids need more current to work as they age and you can have a full 12 volts at the yellow wire and still have this problem. The factory rebuilt Bosch starters have solenoids made in Mexico that can exhibit this problem after a few months. If you have CIS, be aware that the CSV may be spraying fuel everytime you turn the key to start and nothing happens.

If your battery is more than a few years old and you don't use the car every day, I recommend putting it on a charger for a minute before attempting a cold start. Many times the symptom will disappear, especially if it only occurs on a cold start after a few days of idleness. If so, you can debate a new battery or a trickle charger, or both before replacing the starter. You need to get under the car to diagnose the intermittent problem, so I like to fit a starter button, like on old Jag's, in the engine compartment, to test all the wiring at the moment it occurs. Even with the remote switch I have seen this problem on several 911's, some with 1 year old starters, and getting to the bottom of it can be frustrating and expensive. I am also suspicious of the A/C and heater blower relays which are grounded through the solenoid circuit. Good Luck.

[RoninLB]

on 911 starters the first thing I do is see if I can jump it at the starter solenoid when the problem occurs.

if it takes the jump from the large battery black wire lug to the solenoid "start" small lug it's a voltage problem.

also the yellow wire goes through the 14 pin connector.

[Shaun @ Tru6]

new starter solenoids are around $40, takes 5 minutes to put a new one on after starter has been removed.

[Formerly Steve Wilkinson]

It already being winter in the Hudson River Valley and the day after an enormous ice storm here, I must admit I just dropped the 911 off at the local independent Porsche shop and told Tom Florio to either replace the starter solenoid or re-lube it, his choice.

Battery is new, cables and connectors are new, alternator is new, ignition switch electric cassette is new, starter (Tilton) is relatively new, transmission ground strap was replaced when the car was restored five years ago, so I don't think I'm having any of the classic old-Porsche problems.

[RoninLB]

why not tell him to install a momentary direct power start button in the engine compartment while he's in there. Large battery lug to switch, then returned to solenoid "start" lug.

10' of 10ga or 12ga wire, a $15 20amp marine Cole-Herse, and 30 minutes labor.

[Formerly Steve Wilkinson]

Ron, I'm not clear on what that accomplishes. Sounds like a kludge. Can't a German "luxury sports car" be reliably started like a Chevrolet, by turning the ignition key? I'm getting really tired of hearing about all of the incredibly basic failings of this machine... Where is the Luftwaffe when you need them?

[ischmitz]

Originally Posted by Formerly Steve Wilkinson

... I'm getting really tired of hearing about all of the incredibly basic failings of this machine...

hm....a 25 year old car. I wonder how many domestic cars make it to even half that age before the their final journey to the press. And you wouldn't believe how much crap that 200o ML430 is giving me. There is not a week going by w/o something electrical failing. Door switches, lights, window switches, tank sending unit, you name it That makes my 74 ultra-reliable in comparison.

[rick-l]

Let me ramble here and present opinions on how I think starters work that have never been confirmed by an independent source.

When you turn the switch you have to move a fairly heavy piece of steel to compress a spring and close some contacts.

To do this there are two coils of wire around the solenoid plunger, one is fairly large guage, low resistance and would fry the yellow wire if it were engaged continuously. This coil gets the plunger moving and compresses the spring.

The other is a smaller wire, draws less current, and provides a magnetic field just strong enough to hold the plunger in position.

The small coil gets power from the yellow wire and the other side is always grounded to the case of the starter.

The large coil gets power from the yellow wire but gets its ground through the very low resistance of the windings of the starter motor. When the plunger finally moves the contact into position it applies 12 volts to the motor and the other side of this coil which essentially shuts it off. Included in this circuit path are the brushes and segments on the commutator.

How many segments are there on the commutator? I'd guess about 30??? What happens if one winding on the rotor is open? What are the chances you hit that spot?

Edit: What I mean to say is that in order to get current through the pull-in coil you need to have the brushes make contact.

[RoninLB]

Originally Posted by Formerly Steve Wilkinson

Ron, I'm not clear on what that accomplishes.

it provides as much current as the solenoid can absorb.

it's a trouble shooter.

it may also be useful when doing engine work.

imperfect factory wiring and a solenoid & starter that slowly deteriorates and sometimes must operate under extreme conditions is a perfect storm imo. I solenoid drawing 10 amps is not out of the question imo.

you can spend $500 for a new starter install that should be problem free for a year or two. Then it'll be time to party again.


all good info posted but above is only what I do.

I may use the engine compartment switch once or twice/year.