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Car in question: 2002 Renault Thalia 1.5dci (engine same as Clio Mk2, also known as Symbol)

Last autumn, I stopped using this car. Filled the tank, parked in the garage and let it there until spring.

After charging the battery it would however crank very slowly. Tried with different, known good battery and even with two of them in parallel - still slow crank.

I removed the glow plugs to see what happens - and despite not having compression to fight against, still cranks waaay too slow, somewhat quicker though.

When cranking, there is quite a bit of electricity flowing: wires get very warm, and starter motor gets warm to the touch too.

Now this car has the starter in an impossible to reach location (back of the engine, surrounded by the exhaust parts, turbo charger, EGR, etc so it is a major undertaking to even just get it out so trying to avoid doing that - if possible... (if I need to get it out I might have to ask around here on how to do that :) )

What other steps can I try in order to diagnose what the problem is? Another suspect for me could be the high pressure fuel pump but not sure how that gets power.

Additional info:

  • Battery was charged using charger prior to start attempt for several days
  • The starter motor is able to make the whole car move when in gear - almost no change in RPM compared to when only turning the engine
  • Just 10-15 seconds of cranking makes the wires at the battery hot and there is a faint plastic smell even
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    Do you know for sure that the battery posts and battery cable clamps are clean and tight? For example, if you removed the battery for charging, then cleaned the contact surfaces of posts and clamps before reassembly and properly torqued the clamp fasteners, they're good. If not, suggest you do that before further diagnosis. Also, a voltage reading at the battery during cranking will go a long way toward solving this mystery.
    – MTA
    Jun 4, 2023 at 22:21
  • @MTA Thanks - cleaned all connectors and conductive surfaces and even applied contact cleaner spray. Also, checked the battery voltage at the clamps, and even with two batteries in parallel, it drops very low when cranking. Also, if I crank long enough, the - reasonably thick - wires do get really hot, so there is very significant current flowing. I even checked the ground cable to the engine, that seems to be in good shape too. I suspect either the starter motor, or something else has gotten mechanically stuck. Or the starter motor has developed fault resulting in high current and low torque.
    – ppeterka
    Jun 5, 2023 at 7:25

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I think you have a bad battery. Leaving a car to sit for months should not harm a starter, but it can definitely kill a battery.

I was hoping for a more precise answer to my comment about battery voltage while cranking. "Very low" voltage is not very useful for diagnosis. I was hoping for a number! So let's play the percentages and take a reasonable guess at what's happening.

I think your battery has at least one shorted or dead cell. I think you "charged" your battery -- inadequately -- by connecting jumper cables from another car and fast-idling the other car for a few minutes. When you tried to start the car, your battery was still nearly dead. Charging a nearly dead battery takes hours, not minutes.

When you connected two batteries, most of the starting current was trying to get through your jumper cables. Of course the cables got hot, they are too thin to pass full starting current.

A starter that is struggling to crank an engine with a nearly dead battery and/or inadequate voltage coming through too-thin jumper cables will overheat the starter and the cables.

If you want this car to start, you must remove the old battery and install a known good battery into the engine compartment using the car's own battery cables, properly installed and tightened. Forget jumper cables.

If you don't have the equipment to properly charge and test the old battery, take it to a garage or parts store where they can charge it and test it for you. After charging for a few hours or overnight, if it produces less than about 10-10.5 volts under starting load, the battery is lost and must be replaced.

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  • Thanks, testing the battery would not hurt, I'll try to assemble a test load to be able to assess the internal resistance. I added some details to the post to add clarity. I'll get exact numbers of how deep it goes. Actually, the vehicle's own internal cables (original factory parts, not tinkered with) are getting hot when cranking - after being taken off of the proper charger, not by jumper cables. I still suspect either some sort of a short inside the starter, or a mechanical failure of some sort. (Tried the well known battery swap too, actually with a brand new, fully charged one...).
    – ppeterka
    Jun 5, 2023 at 16:44
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    @ppeterka Well, that's the chance we take trying to answer a question that is short on essential details -- a wrong answer! Listen, just to make sure that there is nothing seriously wrong with the engine itself, you can loosen or remove the glow plugs, put the trans in the highest gear, parking brake off, and push the car by hand to move it a short distance. If it moves easily (almost like a car in neutral) and you can see the engine turn, all is well. If you can't move the car pushing it by hand, there is an internal problem with the engine.
    – MTA
    Jun 5, 2023 at 17:39
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    Aha! I think I've got the issue (or at least one of the issues)... I tried the method you suggested and the car felt stuck when pushed forward without glow plugs. So I tried cranking a bit without the plugs - to see what I can notice. And I got lucky: I ran my hand over the engine and felt hot on the end of the engine near the alternator. And bingo: the alternator's pulley was hot. So my guess is now exactly that... BTW without glow plugs the battery reads 10.5V when cranking - with a stuck alternator so I think that is not quite dead yet... Next I'm going to take the belt and try cranking.
    – ppeterka
    Jun 6, 2023 at 15:40
  • @ppeterka Good show! But lucky? Luck comes to the prepared mind. An alternator should spin freely with almost no friction when ignition is off. If your water pump is driven by the same belt, then perhaps check that too. I would expect a seized water pump before a seized alternator after sitting for months. And 10.5 volts is not bad, considering the extra load. Hope this brings you close to a final diagnosis.
    – MTA
    Jun 6, 2023 at 17:03

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