Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault

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Sun 8 Jul 2012 23:58
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - Johnxair

I've had a 5th occurrence of what appears to be a straightforward bad-connection problem on the starter motor. Can anyone offer advice? Is this a common Shogun fault? Have I misdiagnosed the root cause?
The engine refuses to crank on the starter motor, although the panel lights go out, the interior light dims and the battery voltage dips to about 10 volts. No obvious solenoid "Clack" is audible. Removing the solenoid connection (spade terminal) from the starter & connecting the voltmeter to it - you get 12 volts when the starter key is turned. Reconnecting the solenoid & putting the voltmeter onto the starter-side large terminal gives about 10 Volts when the key is turned. Access to this terminal is really difficult with the starter motor on the car, so on each occasion the fault has occurred, I have removed it at this point. This is easier said than done, needing about two and a half feet of socket extension pieces and a UJ to remove the upper bolt.
On each occasion, the starter-side large terminal (the one switched by the solenoid) has been overheated & burnt. Giving this connection a good clean has cleared the fault each time. The starter motor tests ok, giving a good "clack" when the solenoid connection is energised. On the first happening & again last time, I completely stripped the motor, checking for worn brushes or any signs of cracking, but it all looked fine. The last time, I also renewed the nut since there was slight corrosion of the steel.
I realise some of my fault description appears to contradict itself....and this may be a clue to why I haven't solved it. The battery voltage is being pulled down to 10v, suggesting the motor is drawing current, but there isn't an audible "clack" when the solenoid energises & the motor doesn't turn.
Five times I've been lucky that it's let me down at home, since it would be almost impossible to fix at the roadside. It did it today only 2 months after the last time. Can anyone help me get to the bottom of this?

Many thanks

John

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Mon 9 Jul 2012 10:58
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - Peter.N.

I don''t know your specific car but the problem certainly sounds like a faulty starter but its not your run of the mill failure because for it only to be pulling the voltage down to 10 volts would indicate that its not drawing the full current, unless you have a huge battery I would expect to go somewhat lower than that. The fact that you cant hear the solonoid engage but it is still drawing current would point to the solonoid itself as being the problem I have had one develop intermittent shorted turns which causes insufficient flux to pull in but a fairly heavy current draw, if this is the problem the solonoid should be getting hot.

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Mon 9 Jul 2012 13:37
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - Johnxair

Thanks Peter, I think you have a good point about suspecting the solenoid. The first time it happened (about 4 or 5 years ago) I tried to measure the solenoid's current draw. Not having a heavy enough ammeter, I did a d.c. resistance check & used Ohms Law. From memory, this gave an estimate of about 30 A, which I took with a pinch of salt because the inductive effect of the solenoid winding will reduce this somewhat. I haven't got a resistance meter which is good enough at the low-end range to make an accurate measurement at present. The battery is about 95Ah, heavy duty & in good order.

This morning I removed & cleaned the switched-live terminal on the starter (previously reported as burnt). There was no burning as far as I could see, but I did it without removing the starter from the car. On reassembly, the first attempt at starting resulted in the fault still being there. The next 3 starts were sucessful and normal. When it cranks, it does so at normal starter speed & when it doesn't....it doesn't. It never cranks slowly.

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Mon 9 Jul 2012 17:54
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - Peter.N.
Certainly sounds like the solonoid, you could try shorting the heavy terminals together with an old screwdriver, if it turns the starter under fault conditions you have your answer. I am sure you are aware of the currents involved which is why I say and 'old screwdriver'.
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Tue 10 Jul 2012 21:17
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - Johnxair

I believe it's going to be around 450 Amps, which needs a certain amount of respect! When it happened last (2 months ago) I used a flying lead with a spade terminal & connected the battery directly to the solenoid. Nothing happened! The baffling thing is why playing with the switched-live contact clears the fault. The problem goes away for up to a year, then reappears & immobilises the car.

I think a replacement starter motor is the next plan. I really appreciate your input, Peter.

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Tue 10 Jul 2012 22:40
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - elekie&a/c doctor

Does look like the starter is at fault,but have you checked the engine/chassis/battery earth strap?A poor connection here will give the same symptoms.hth

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Wed 11 Jul 2012 11:06
Mitsubishi Shogun 3.2 DID Auto LWB 2002 - Starter circuit fault - Peter.N.
I did have a strange fault on my sons pickup where the starter operated intermittently, by complete accident I found that although the terminals were tight one of them was not making contact. I only found this when I shorted the tag to the bolt and it sprung into life. I can only conclude that some electrolytic action had turnd the surface into an insulator/semiconductor, a good clean cured the problem.
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