850 will not start

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850 will not start

Tiller

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Mar 29, 2014
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For the last 3-4 days my 1970's Fiat 850 have had a lumpy start.
Just like when the battery starts to run flat.
And yesterday it would not start. It was just like the battery was out of juice.
I charged the battery and it showed 12,7v.
I tried to start, but same "bad battery" symptoms.
I measured the constant 12v at the starter and it also showed 12,7v.

But the car has the same symptoms as a bad battery when i turn the ignition...

What could be wrong?
 
Check the ground wire from battery to body
 
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Measure the battery voltage while the engine is cranking on stater motor , report what it is.
 
Check the ground wire from battery to body

As jackwhoo says, check that black battery cable - the terminal may be corroded and needs cleaning, or where it attaches to earth - undo the nut that holds it to earth on the block/bodywork and retighten it. A 'bad earth' can cause the symptoms you describe.

A quick check if you have jump leads/booster cables... attach one end of the cable to the negative terminal, and the other end to any suitable earthing point on the engine or inner wing. If the car starts okay it's then pointing to a battery terminal/corroded lead/poor earth problem
 
The battery measures 11,8 when cranking.
The positive to the starter that turns on when cranking measures 10,9v.

It occupationally turns the engine (very very slow), but most of the attempt i only hear a clunk from the starter when turning the ignition
 
There is a problem causing the 0.9 volt drop between battery and other point you are measuring.
I am surprised there hasn't been a smell of burning or smoke from the point of resistance causing the voltage drop.

Check the ground wire from your battery as mentioned several times.
 
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As well as checking that the earth lead from the battery to the body is sound, don't forget that there is, iirc, another earth lead from the engine/gearbox to the body. This might be a braided earth lead/strap connecting the waterpump to the body or a black insulated lead under the car connecting the gearbox bellhousing to the body. The above suggestion of using a battery jumper cable to temporarily provide a good earth is a great idea.

Some Fiats (I'm not sure if this applies to the 850) use spot-welds to attach earth leads to the body, corrosion if severe can cause trouble here. You can either drill a hole through the earth lead flag terminal and body and insert a nut and bolt, having cleaned both sides of the hole, or fit a separate earth lead.

If the earths check out ok, it might be time to take a look at the starter solenoid mounted on top of the starter motor. This has internal contacts (like a big switch) which can burn or erode. You can compare the voltage at both large terminals while operating the starter to check for this.

Hth,

Al.
 
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The battery measures 11,8 when cranking.
The positive to the starter that turns on when cranking measures 10,9v.

It occupationally turns the engine (very very slow), but most of the attempt i only hear a clunk from the starter when turning the ignition

I'm not sure where exactly you're measuring the above two voltages but if you're measuring both large terminals on the starter motor solenoid then the solenoid is faulty, you shouldn't have more than 0.5 v difference, preferably less.

When you say 'It occupationally turns the engine (very very slow)'
do you mean it has always done this or only recently?

Fiat 850's used to wear out the carbon brushes inside the starter motor. Also it was found that undercutting the insulation between the commutator segments (not normal practice on car starter motors!) helped avoid slow turning of the starter motor when the engine was hot

Al.
 
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Just remembered, some 850's had an engine to body earth lead attached to one of the studs? holding the starter motor in place.

Al.
 
Took the starter motor out and the bushings were worn.
Changed the bushings, cleaned the connections and now it works again :)
 
I have an 817 engine ground crank new bearings when warm looses oil pressure never seen an oil system like this. help
 
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