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Wiring difficulty - Landcrab
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peppiB



Joined: 30 Jun 2008
Posts: 686
Location: Newcastle upon Tyne

PostPosted: Tue Feb 12, 2013 3:53 pm    Post subject: Wiring difficulty - Landcrab Reply with quote

My starter motor was sluggish so took it off and cleaned it. Now the car turns over fine but wont fire. There is 12v at the positive coil terminal until I turn the starter then it drops to zero. A fresh cable from the fuse box (terminal A3, which is the correct one) to the coil and she fires and runs fine BUT the oil warning lamp doesn't work. Reconnect the original wire and the oil warning light comes on but she won't start. It's driving me nuts!! Anyone any ideas?
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1252
Location: Nottingham

PostPosted: Tue Feb 12, 2013 8:03 pm    Post subject: Reply with quote

Depends on car but it is likely to be an incorrectly wired ignition switch or burnt contacts within that cuts off supply when in starting position
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Wed Feb 13, 2013 7:56 am    Post subject: Reply with quote

I'd agree with Phil; when an electrical connection is poor or disconnected, the load can get routed via other components, with all sorts of odd results.

You may get 12v on the coil when the points are open, as there is no load, if the 12v is getting there via other components, as soon as the load is applied (points close) the voltage gets distributed proportional to the various resistance in the "circuit" as the coil is a fairly low resistance, the voltage will drop to virtually nothing.

One other possibility that crossed my mind (as you have been servicing the starter motor) do you have a ballast set up on the coil? if so when starting the 6v coil gets a 12v feed via the starter motor feed, has this feed to the coil been disturbed? Look for a white with yellow wire (normal colour for ballast feed) is it correctly connected to the ballast resistor at one end and the starter motor or solenoid at the other.

Dave
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peppiB



Joined: 30 Jun 2008
Posts: 686
Location: Newcastle upon Tyne

PostPosted: Wed Feb 13, 2013 11:49 am    Post subject: Reply with quote

Thanks guys. Don't think it can be a fault in the ignition switch as when a fresh cable is used the switch works fine.

There isn't a feed from the starter motor to the coil - the only wire to the starter motor is the one from the solenoid, earthed back via engine and body.

I suspect a weak connection somewhere in the circuit - it is just a question of finding it - and running without an oil warning light til I do!

Will have a couple of days rest to recover from cleaning starter motor (am in wheelchair) then tackle it again
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Penman



Joined: 23 Nov 2007
Posts: 4751
Location: Swindon, Wilts.

PostPosted: Wed Feb 13, 2013 1:36 pm    Post subject: Reply with quote

Hi
With the starter now working energetically could it be moving the engine about more?
If so flexing the LT feed wire could be revealing/causing a break in the continuity through the copper.

Disconnect the feed from the coil connect that end through a test bulb to a good earth and then with the engine switched on wiggle the wire about at any point where it can flex if the engine moves, if the light flickers on/off then there is a break somewhere inside the insulation.

I had a heavy starter cable fail once because of engine movement (Fiesta not Landcrab).
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Last edited by Penman on Wed Feb 13, 2013 4:30 pm; edited 1 time in total
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peppiB



Joined: 30 Jun 2008
Posts: 686
Location: Newcastle upon Tyne

PostPosted: Wed Feb 13, 2013 3:49 pm    Post subject: Reply with quote

Thanks Penman - that is a great idea. I think there is a weak point/break somewhere in the LT lead causing the problem, and that is a great way to find it
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emmerson



Joined: 30 Sep 2008
Posts: 1268
Location: South East Wales

PostPosted: Wed Feb 13, 2013 6:06 pm    Post subject: Reply with quote

By the time the oil light comes on, it's too late anyway!
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peppiB



Joined: 30 Jun 2008
Posts: 686
Location: Newcastle upon Tyne

PostPosted: Wed Feb 13, 2013 8:10 pm    Post subject: Reply with quote

But if the light comes on you are prepared for the 'bang' when it comes! Shocked
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Wed Feb 13, 2013 11:44 pm    Post subject: Reply with quote

Nearly always fitted oil pressure gauges to my cars which has saved me a big bill on at least one occasion Cool
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peppiB



Joined: 30 Jun 2008
Posts: 686
Location: Newcastle upon Tyne

PostPosted: Thu Feb 14, 2013 11:36 am    Post subject: Reply with quote

Back in 1965 mate of mine fitted a gauge to his mini. The oil warning light came on but the gauge showed a good pressure so he thought the light faulty, then .... bang. It was a faulty gauge. Not been well enough to do any proper work as yet but had a 'fiddle' late yesterday and found 1 spade connector hanging on by a thread. Not renewed it yet but it is a starting point
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Thu Feb 14, 2013 3:10 pm    Post subject: Reply with quote

Driving a Bedford CF in the 80's on the M62 near Heartshead Services; in the space of 10 seconds, I heard a ticking noise, the oil pressure light came on, just before a piston escaped Shocked

I did wonder if there had been a gauge, if I may have spotted the oil pressure change and possibly been able to stop before things got terminal Sad

It was a works van that had just had a recon engine fitted, my boss contacted the engine supplier, their warranty procedure was to return the engine for inspection, to the quality department...... on the Isle of Sky...

So we fitted an engine from a scrapped van!!

Dave
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