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        General >> Problems >> Starter motor solenoid going bad ?
        
(Message started by: Jonnycab on Jul 30^th, 2010, 2:30am)

Title: Starter motor solenoid going bad ?
Post by Jonnycab on Jul 30^th, 2010, 2:30am

Got a starting problem....in that occasionally when starting the car, the starter doesn't engage & all I get is a sound like a 'machine gun' coming from the starter motor. After a few attempts it finally engages & the engine comes to life.

....so obviously the starter motor is on the way out....or is it ? :-/

The reason I'm undecided, is because when this happens, the dash needles flick about & the dash resets, as though there is a problem with the battery ???

Okay, so maybe it's a battery problem ?....but the battery is under a year old. It's a full battery tray size 'type 100' job (round post) & battery voltage reads between 12.4 - 12.8 volts before starting (depends on how long I've been sitting on the taxi rank with the engine off & roof light/radio on). Also the alternator is charging at 14.4 volts & all battery leads are on nice & tight.

9 times out of 10, the car fires up as soon as the key is turned, so I'm pretty sure it's the starter motor solenoid at fault, but am not sure why the dials are flicking & the dash is resetting.....any thoughts ? :)

Title: Re: Starter motor solenoid going bad ?
Post by Tompion on Jul 30^th, 2010, 4:54am

It certainly sounds like the battery.
I’m sure you know, but it is easy to get caught out – if you’re checking the voltage via the instrument diagnostics the needles will always flick round next time you turn on the ignition.

I’m not sure where the instrument cluster picks up its earth if it’s from the main earth & not from that extra earth wire to the battery then check that dodgy looking main earth to the bodywork & bodywork to engine.

A car I had a while back gave me starting problems which turned out to be the crimp on the earth strap.
You could leave a jump lead from the battery earth to a decent engine earth to see if the problem goes.

Title: Re: Starter motor solenoid going bad ?
Post by Highlander on Jul 30^th, 2010, 9:24am

Want a starter motor to try Jonny?

I have about half a dozen lying here! :)

Title: Re: Starter motor solenoid going bad ?
Post by Oilyspark on Jul 30^th, 2010, 2:48pm

Try turning various lights on, and see if they dim excessively when you get the machine-gun noise. If so it is most likely a bad connection or the battery. The fact that it usually works fine makes me think it's not so likely to be the battery itself, but a corroded terminal that has high and variable resistance. After a start attempt, the offending connection may well be warm or hot to the touch.

Lucien

Title: Re: Starter motor solenoid going bad ?
Post by Mike H on Jul 30^th, 2010, 3:07pm

I concur, low battery seems most likely.

I think it's easy to underestimate how quickly it gets depleted. Doesn't matter how new the battery is if you're sitting idle using juice for longer than you can recharge it by actual driving it'll go down. An idling engine doesn't do it ether. Add every time you turn the key to start that's X hundred Amps which may need 30 minutes or so of usefully high revs to actually replenish.

Example, I was on a camping trip last weekend for 4 days, 135m run there so well charged battery on arrival.

Move the car a couple of times, opening closing windows a few times cos of the hot weather, little bit of country lane driving (i.e. <=30mph) looking for pubs and so on.

Had the radio on for a couple of hours while I was packing up to leave, when it comes to start the engine, got the flicking needles! It had gone down that much in just 4 days.

Title: Re: Starter motor solenoid going bad ?
Post by Mike H on Jul 30^th, 2010, 3:11pm

on 07/30/10 at 14:48:09, Oilyspark wrote:

The fact that it usually works fine makes me think it's not so likely to be the battery itself, but a corroded terminal that has high and variable resistance.

Despite my forgoing that's a good point actually

An old favourite 'cure' was to very lightly tap the battery terminals with a hammer ;D

Title: Re: Starter motor solenoid going bad ?
Post by Jonnycab on Jul 30^th, 2010, 5:46pm

Thanks for the tips guys....I nipped down the garage this morning & had the battery tested with one of those big two pronged testers & the battery checks out fine.

I've checked all earth straps for tightness & found one which could possibly be a cause.....The nut holding the short earth lead to the solenoid from the starter motor wasn't really tight. I managed to nip it up half a turn & I'll just have see how it goes tonight.

Stuart, thanks for the offer of the starter :), but there's no point sending it a the moment, cos I'm off on me hols on Sunday.....a weeks camping in sunny Norfolk...I hope ;)

Title: Re: Starter motor solenoid going bad ?
Post by Highlander on Jul 30^th, 2010, 5:51pm

on 07/30/10 at 17:46:40, Jonnycab wrote:

The nut holding the short earth lead to the solenoid from the starter motor wasn't really tight. I managed to nip it up half a turn & I'll just have see how it goes tonight.

Sounds like you've found the problem :)

Title: Re: Starter motor solenoid going bad ?
Post by Oilyspark on Jul 30^th, 2010, 6:11pm

I'm not convinced about that short link cable. It's not an earth, it's the feed from the solenoid contacts to the motor. If it were making poor contact, the starter itself might be erratic or sluggish but the problem would not influence the instruments or other equipment, since it would not cause voltage drop in the shared parts of the circuit.

Lucien

Title: Re: Starter motor solenoid going bad ?
Post by Cosray on Jul 30^th, 2010, 9:55pm

Jonnycab, do the following test please.

Put the car in a dark area, no lights on, have the engine idle and watch your charging light on the dash. It is probably glowing very faintly which in daylight you will not notice besides - the wheelspokes are in the way!

I gave seen many Scorpio's here with identical symptoms and problems with a faint glowing charging light. It means the battery is starving day by day, whether you dirve around town or motorway, it is never enough.

Almost always diodebridges packs in the generator are gone; like 1 pack out the two or three. It is a € 50 repair job and batterylife is up to three years minimum.

Here's the schematics:
http://public.blu.livefilestore.com/y1pCTGnp4tvDRmAraxz2bnq8stM708rOMgtqvepu5nUgZNqGpE9ZJOTfZ-XrcpfXHDWw7zAxx6wIFQ-SvGa-jehog/CHARGING%20SYSTEM.pdf?download&psid=1

HTH
Ray

Title: Re: Starter motor solenoid going bad ?
Post by Jonnycab on Jul 31^st, 2010, 2:20am

Hi Ray, I already thought of that one (I work nights) & there is no faintly glowing charging light :)

Oilyspark, are you sure it's not an earth ?....It's a thick braided wire, one end bolted to the solenoid & the other end attached to the body of the motor :)

Anyway, touch wood, I've had no problems tonight. That doesn't necassarily mean it's fixed though, as the car can go for days without having any problem....only time will tell ;)

Title: Re: Starter motor solenoid going bad ?
Post by lesterlad aka Rodders on Jul 31^st, 2010, 9:47am

I used to have the same intermittent problem on my old granny 4x4.
It would start with no problems for a month or more, another month I'd get the fault a couple of times in a week.
It was a (thinnish) wire that was attached to the starter by a push on type connector, if it didn't turn over I'd put my hand under the starter and give the wire a wiggle, instant turn over after that.

Title: Re: Starter motor solenoid going bad ?
Post by Mike H on Jul 31^st, 2010, 11:02am

Does sound quite typical. A bad contact causes a resistance which drops the Volage.

So like the "machine gun effect" is because the solenoid is energised OK, but then this extra current through the resistance causes the Voltage to drop too low so the solenoid drops out, then it's OK again so back on for 2nd attempt, then it's not, etc. etc.

Did I tell you the story of my mini where the entire electrical supply for the whole car was off just one quarter inch push-on terminal? ;D

Never went anywhere without some good pliers to crimp it up again whenever it got overheated and went loose.

Title: Re: Starter motor solenoid going bad ?
Post by Cosray on Aug 1^st, 2010, 10:21am

Scorpio friend had identical problem the other day. Sometimes the "machinegun" would fire.

We found the the startermotor employs two relaycoils/solenoids/coils in parallel.

Once the IGNkey provides current the the two of them it makes the startmotor engine contacts close for big power. Then the first coil is shorted by design and is powerless, whilst the second holds the contacts locked in place as long as the IGNkey provides current during a long start.

The second solenoid however being dirty proved to be unable the hold the contact once the first was shorted.

So the contacts opened, enaging the first solenoid again, closing the contacts etc. and the system started to oscillate.

Remedy: clean solenoids, both.

Look here for schematics:

http://cid-eb36f845ea9b8fb6.office.live.com/self.aspx/WIRING%20DIAGRAMS/STARTING%20SYSTEMS.pdf

HTH
Ray

Title: Re: Starter motor solenoid going bad ?
Post by Oilyspark on Aug 1^st, 2010, 10:46am

Ray makes a good point there - if the hold coil is intermittent or disconnected, the solenoid with just the pull-in coil resembles a kind of electric bell arrangement. I am unsure whether this would make your dashboard act funny though, unless the pulsing voltage at the battery terminals causes it a headache!

Title: Re: Starter motor solenoid going bad ?
Post by Cosray on Aug 1^st, 2010, 10:53am

Ah yes Oilyspark, I forget to mention friend had the flicking needles too, which of course we first attributed to a weak battery.

From earlier experience I remember the instrument cluster resets when line voltage drops below 10 V and what with the currents and inductionvoltages involved when staccato starting the engine that could easily happen, however short.

Ray

Title: Re: Starter motor solenoid going bad ?
Post by Jonnycab on Aug 6^th, 2010, 11:36pm

Literally just got home from a weeks camping using the wifes 2.3 Scorp estate as the workhorse.....behaved impeccably as usual with a full boot load & full up 450 litre roof box.
Started my 2.3 (to move it from the estates usual parking space in front of the house) & it fired up first time on the button, so I think we can safely assume that the battery is okay ;).

Interesting reading about these relay/coils. I'm useless at reading schematics, but am I to assume that these relay/coils are the pair of heavy contacts that are inside the solenoid ?....thus making it a problem with the starter motor solenoid, as I first thought ? ;)......:)

Title: Re: Starter motor solenoid going bad ?
Post by Cosray on Aug 7^th, 2010, 6:24am

Hi Jonnny, good everything worked OK for you but mind the lurking electrical Scorpio gremlins...

Here's a bit of light reading on the startercircuit. Though written for VW it is principally correct. Scorpio uses two coils though - one for engaging, one for holding the contacts.

http://www.ramva.org/dragenwagen/starter.html

HTH,
Ray

Title: Re: Starter motor solenoid going bad ?
Post by Mike H on Aug 7^th, 2010, 10:21am

Glad to see the back of those inertia type Bendix starters ;D

The pre-engagement type seems pretty universal now. Even got it on my two motorbikes. Also got a really good workshop manual for one of them that goes into great detail for overhauling the motor.

With a solenoid you can have a high power energising winding and a low power holding winding.

How it works is the high power winding is in series with the motor windings (field magnets and armature and brushes); these have very low resistance compared with the solenoid hence it operates. To do this the high power winding is connected across the starter terminals.

When the moving disc contact closes the terminals it shorts out the high power winding, leaving just the holding winding (other end goes to earth). Simultaneously the whole battery voltage is then applied to the motor windings.

If say the holding winding was broken it couldn't hold it and would keep "buzzing"

What isn't obvious is that the solenoid is doing two things, it's acting like a solenoid to engage the pinion, plus, it's acting like a relay switch to make the motor work. For the old bendix starter motors the solenoid was typically separate and was basically just a big relay. Had nothing whatsoever to do with actually engaging the pinion.

And before that it was a big switch mounted in the floor that you pressed with you foot ;D

Title: Re: Starter motor solenoid going bad ?
Post by TomP on Dec 13^th, 2010, 11:17am

Hi Jonny,

Did you ever get any more problems with this? This is the exact same problem I have my my 2.9 12v at the moment. Satrted getting the 'machine-gun' noise but starter motor would eventually kick-in. But now this weekend only 'machine-gun' noise and no starting. Although the battery isn't new, like, you, I feel it isn't battery related.

Looking at the notes on changing the starter, is it and the solenoid only accessible from underneath the car?

Meant to be picking up my daughter from uni (with all her gear) at the weekend, help!!!

Title: Re: Starter motor solenoid going bad ?
Post by Highlander on Dec 13^th, 2010, 11:21am

on 07/30/10 at 17:46:40, Jonnycab wrote:

I've checked all earth straps for tightness & found one which could possibly be a cause.....The nut holding the short earth lead to the solenoid from the starter motor wasn't really tight. I managed to nip it up half a turn & I'll just have see how it goes tonight.

Title: Re: Starter motor solenoid going bad ?
Post by Jonnycab on Dec 14^th, 2010, 12:06am

on 12/13/10 at 11:17:08, TomP wrote:

Hi Tom....Since I tightened that strap on the starter back in July, I've not had any problems with the car 'machine gunning' when starting....& it's still got the same battery :)

....and yes, you have to lay under the car to get to the starter ;)

Title: Re: Starter motor solenoid going bad ?
Post by TomP on Dec 31^st, 2010, 7:22pm

The cars been left idle for a couple of weeks. Battery was flat today so have charged for a few hours. Getting the 'machine gun' noise now but does not start. Got underneath, removed lower engine cover. Could see 2 nuts on the solenoid (I think) tried to tighten but they were fine. Looks like a smaller nut in mddle (of solenoid?) but bit difficut to get spanner on so couldn't get to, although cable seemed tight.

Jonny, are these the 3 wires you were referring too? Are there any others I should check? Guess my next step is to remove starter motor so garage can test...

Title: Re: Starter motor solenoid going bad ?
Post by gozz on Dec 31^st, 2010, 10:12pm

Have you given the starter a d**ned good clout whilst someone turns the key,if that temporarily cures it you need another unit. We assume the battery is OK ?
GOZZ.

Title: Re: Starter motor solenoid going bad ?
Post by TomP on Jan 1^st, 2011, 1:02pm

Thanks for help and suggestions, much appreciated. After trying to tighten up connections on starter/solenoid yesterday (without any positive effect) I left the battery charging overnight and surprise surprise the car started no problem this morning....no machine gune noise, fired first time. Tried starting a few more time and seems fine. I'm going to take it fo a run later then leave it overnight and see what happens. Not sure how old the battery is, but it's over 4 years, so maybe time for a new one.

Any suggestions on what type/best place to get a battery?

Title: Re: Starter motor solenoid going bad ?
Post by Simmo on Jan 1^st, 2011, 4:57pm

The battery details are Here (http://www.fordscorpio.co.uk/battery.htm). The 71ah and 650cca are the vital figures. :)