1981 FI starter problems

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fiatfam
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1981 FI starter problems

Post by fiatfam » Thu Jul 25, 2019 4:38 pm

I am having a problem with my starter. It seems to be drawing a lot of power and cranks slowly even with a fully charged battery. There are times it won't operate at all. Does this sound like a bad starter or solenoid. I am thinking of replacing it with a new high torque version. I will be doing this on a 1981 FI spider. Will I have to remove the intake to gain access to the starter bolts?
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bartigue
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Re: 1981 FI starter problems

Post by bartigue » Thu Jul 25, 2019 6:08 pm

Sounds like a bad starter (the big part). Solenoid sounds like it is working as it's just a big power relay. A gear reduction starter will be nice to have.

On the FI car access is worse than the other cars, and generally speaking it is bad on all of them. Unplug the battery, disconnect the electrical part of the starter and solenoid, then work the bolts out (the hardest part). You'll be able to wrangle it out of the bottom of the car. Easier to install than remove and the reduction starters are smaller, thankfully.
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18Fiatsandcounting
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Re: 1981 FI starter problems

Post by 18Fiatsandcounting » Thu Jul 25, 2019 7:41 pm

I would also check the battery terminals and cables. They may look OK, but all it takes is some corrosion on the terminal connections to really drop the voltage that the starter actually sees.

If you have a voltmeter, the easiest way to do this is to put your voltmeter leads directly on the battery posts (not the connector). Red to positive and black to negative. Have an assistant crank the engine, and if the voltage drops below 9 volts or so, your battery may not be up to snuff even though it is fully charged. Over 9 volts or so, probably fine. You may have to remove some spark plug wires to allow you to crank the engine for a few seconds to get a good reading when the battery is really under load. Next, put the voltmeter leads directly on the terminal connectors and crank the starter again. If your voltage drops to the same voltage as before, your connections are good. If the voltage is lower than before, one or both of your connections needs to be cleaned up and retightened.

If you want to get really adventuresome with your voltmeter, you can connect it between a good ground and the fat cable that connects to the starter motor solenoid. Crank the engine, and if the voltage is less than 8 or 9 volts or so, your issue is likely a weak battery or the connections from battery to starter. Also an old battery may be fully charged and able to run lights and such, but when asked to provide 200-300 amps, just can't do it anymore.

-Bryan
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Re: 1981 FI starter problems

Post by bartigue » Thu Jul 25, 2019 7:51 pm

Good point, Bryan, I jumped right to "just replace it" - which maybe isn't the right answer. Last time I worked on someone's starter they had installed new battery terminals. The terminals were painted on the mating surfaces. So it delivered 12V but when you hit the starter it all went dead flat. Took a bit before I decided to remove the battery and saw the paint. Now I usually clean the terminals first (and unfortunately assume others do as well and should know better!)
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zonker
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Re: 1981 FI starter problems

Post by zonker » Thu Jul 25, 2019 11:00 pm

On my 1971 field rescue spider, I had a slow crank issue too, even with a decent battery, I come to find out the main lead coming from the starter body to the lower terminal on the solenoid was corroded enough to make a great deal of resistance. I loosened the nut and retorqued it, problem solved (until the bendix drive failed but that's another issue).
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spider2081
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Re: 1981 FI starter problems

Post by spider2081 » Fri Jul 26, 2019 8:44 am

old school test for poor connections is to feel the connection for heat. If a connection is warm its likely poor.

Recently I cam across a Spider that was cranking too slow to start. The car had one of those green knob battery disconnect switches on the negative posts. Right after the owner showed me his problem I felt his battery terminals. The positive felt cool but the disconnect switch felt warm. I removed the switch and connected the negative cable directly to the battery. Car starter right up.

Feeling connections in the starting/charging system of our cars is fairly easy and requires no meters or tools. The feel test has also worked for me on the fuse panel to isolate poor connections.
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18Fiatsandcounting
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Re: 1981 FI starter problems

Post by 18Fiatsandcounting » Fri Jul 26, 2019 2:13 pm

Good idea on the heat test, and since I also dabble in tube radios and amplifiers, I of course had to go off and do some quick calculations.

If a poor battery connection is dropping (losing) 2 volts across it, and the starter is drawing 100 amps under those conditions, Ohm's Law tells us that the resistance across that poor connection is 0.02 ohms. Power is voltage squared divided by the resistance, so that would be 4 divided by 0.02, or 200 watts dissipated as heat. Definitely would be noticeable by touch after a few seconds.

-Bryan
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