starter motor help please

[davehaynes1]

Good evening all

Ive got an old truck 1990 that has always had intermittent starting issues whilst ive owned it.. As far as i am aware the battery is in good working condition.

a quick run down of the problem.
I turn the key to IGN and let the glows warm up, when the glow light goes out i continue to start.
most of the time is starts first pop, straight away.
sometimes, maybe 1 in 10 starts it doesnt start straight away so i keep the key turned to start and after maybe 5 seconds it starts.

If i release the key from the start position without managing to start the truck it will do nothing no matter how many times i turn the key to start again i get NOTHING, no relay click, no starter noise, nothing at all.
Because of this i have got into the habit of never releasing the key from the start position until the truck has started

But today was one of the bad days..... turned key to start, nothing, kept key in start position for a good 20 secs, still nothing.
Released and tried again a few times, nothing
got a battery pack on the vehicle, nothing
hooked up another running vehicle with jump leads, nothing
swapped battery with a known good battery from another vehicle, still nothing
then, with the known good battery installed i had a helper hold the key in start position and i gave the starter a few light taps and it started up.
i then turned it off and started it back up again a good 20 times with no problems


When i got home i pulled the starter out, all contacts look good, nice and clean with no corrosion.
i pulled everything apart and brushes look good, still have alot of force pushing then onto the communicator.

Ive phoned local parts suppliers and none can source a new starter and have recommended either get one from a scrap yard or have my one rewound.

What is the cause of the starter motor 'sticking'? could a rewind fix this or would the issue be elsewhere?

Ive attached a photo of the kind of starter motor my vehicle has. Ive noticed the alot of starters have the electric motor directly behind the gearset with a solenoid attatched above.
Does this mean my starter doesnt have a solenoid?? i was under the impression from what ive read elsewhere that the solenoid is what 'sticks'

Cheers

 

[James]

They refer to the solenoid in that diagram as a magnetic switch.

 

[davehaynes1]

ok i see.
When i gave the starter a tap today and it started afterwards, the part i tapped was the motor itself because the solenoid/magnetic switch sits under it on the truck.

Is there anyway the motor itself can get stuck/ jammed?? i know people always talk about a sticky solenoid, never a sticky electric motor
or would you guess the tap sufficient to make the shock travel down to the solenoid/magnetic switch

 

[James]

Could be that a motor brush is sticking slightly, a poor connection of any wire,

 

[James]

It would be worth checking that the voltage to the starter solenoid (small wire) is 12v when trying to start, particularly when it is in fault mode.

 

[davehaynes1]

would this then indicate a fault in the ignition switch itself?

 

[plugsandsparks]

Fortunately there are only a few components that can do what you describe:

1. Ignition Switch (this can be checked with a multimeter on the wiring for the starter (small wire) if you can get to it.
2. All big cable connections : Battery to starter, battery to chassis, engine block to chassis
3. Starter Solenoid - located at starter, it is where the big wire from the battery goes to. If you dont even here a click then its not likely to be the starter motor sticking as you would here the click which is the solenoid.

I would start with all connections first, they really do need to be in top shape.

Otherwise replace the whole starter motor assembly including motor and solenoid switch.

Might also be worth checking all glow plugs are actually working (if you can get to them by checking the resistance using a multimeter between cable connection and engine.

Hope this helps

P&S

 

[davehaynes1]

I'm pretty sure connections are good, battery connections are definitely good, as are starter motor.
I haven't checked engine block earth.

I'm still a little confused about the starter solenoid as I don't have a 'normal' starter motor with a direct drive motor and a solenoid on the top.
After a little research it appears I have a gear drive starter with a magnetic switch. Not sure if this can still get 'stuck' like a conventional solenoid?

I'm an starting to lay suspicion on the ignition switch but won't be able to diagnose unless I'm very lucky/unlucky and have the issue occur again whilst I have someone under the truck with a multimeter.....

 

[plugsandsparks]

Some multimeters have an audible tone option, if you can ask everyone to be quiet, you may be able to hear it when you turn the switch, just jam the probes in and operate the switch and listen for the tone. Fiddle the switch to see if there is any play.
As for the starter, one way or another there must be a substantial "relay" , "switch" to take the signal from the ignition switch and be able to switch 100's of amps. As these are substantial you will hear the click for sure. Some starters use a clutch, some use a throw gear, either way if you dont hear a click the "relay" is not doing its thing.

 

[davehaynes1]

So I've been back under the truck today.
I've installed the starter motor again after cleaning up the brushes and communicator and all contact points for the wiring harness.

I've been for a drive and had no issues, but I've had this before. It'll work fine for weeks and weeks and then one day it doesn't want to do anything.

Battery reading show 12.7 when truck is off and drops to 9.5 - 10 when the truck is starting so I'm pretty sure now that the battery is ok.

I can't see how I can test anything else unless I can replicate the problem, which I obviously can't. If I could do something to replicate the problem I would know what was at fault.

I'm really at a loss here

 

[davehaynes1]

I've also been on a hunt for the starter relay.
When I had the starter motor unhooked and unbolted from the engine I tried to start it and listen out for a relay.
I found two, one for the glow plugs and one for the cooling fan.
There seems to be no relay in the cab of the truck for the starter motor

 

[plugsandsparks]

Sorry i think i may have confused the situation - "relay" is a general term in this context. The starter "relay" nowadays is usually located within the starter motor casing, sometimes it can be remote but the clue is the massive cables that must attach to it. The diagram you posted indicates the "relay" is within the starter motor housing. Other names for this "relay" as used for electric starter applications are: "Solenoid" - "starter switch" - "starter contactor" - the reason for all these differences is that the "relay" may be combined with other functions like operating the starter mechanism.

To be definitive the only way to really test this is using two people.
1. Put everything back together as normal.
2. Wait for the incident to happen.
3. Place voltmeter (multimeter on 12DC range) - red probe held on starter small wire whilst its still connected (you may need to expose either the wire or get probe onto an exposed part of the terminal , there should only be one small wire. Place other probe on engine block.
4. Get helper to turn ignition key.
5. If you get 12V but no clicking, its the starter solenoid
6. If you dont get 12V its either the ignition switch or engine block earth or power to ignition switch upstream.

Whilst the above is as general as i can make it, a photo of the starter showing all attached wiring will help determine if the "relay" is within the starter housing or remote.