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Cranks slow or not at all on re-start when car run for more than a half-hour

Battery was replaced about three weeks ago after noticing slow cranking start-ups. Prior to that, the most recent repair was to replace a faulty coil assembly and ignition wires about nine months ago. The faulty coil assembly caused the car to sputter and lose power.

Currently, after the car has been run for at least a half-hour, and after the engine has been off for a few minutes, 5 or so, the engine will barely crank or won’t turn over at all on re-start. I found that after letting the car rest and cool for a little while, I can get it to start, but it cranks very slowly. Once started, the car runs fine. The car always starts fine and cranks over very strongly if the engine is cold.

I’ve had the charging system and alternator checked, and everything appears to be normal. I’ve not had any warning lights illuminate on the dash. Fluid levels are all normal. The engine runs fine and does not overheat. Battery connections are tight and wires look okay.

Any ideas on what else to check or what could be done to diagnose the problem?

The problem might be caused from a worn out starter being effected by the engine heat. Or a starter that’s heat soaking.

A worn out starter may function normally when cold. But as it gets hot and things move/expand inside the starter it can cause the starter to drag which causes it to turn slowly.

0ne way to check for this is, test the amp draw of the starter when cold. Then once the engine is up to temperature, test the amp draw of the starter again. If the amp draw is significantly higher when hot, the starter is worn out.

Tester

+1 for Tester. A heat soaked starter that is going bad is a royal pain in the behind.

I had the exact same problem and coincidentally it was on a Ford Taurus. I had a starter replaced because the starter drive would not always engage the flywheel. I took the car to Western Auto and had the starter replaced. I then began having the exact same problem as the OP. I went back to Western Auto and they claimed that they couldn’t duplicate the problem. I then went to an independent garage that I had never visited before. The car was hot and cranked very slowly. They did the exact same test the Tester prescribed. The current draw was excessive. The prorietor wrote down the current draw on his letterhead and told me to take it back to Western Auto. There was no charge. When I showed the findings to the manager of Western Auto, the starter was replaced on the spot. This was 22 years ago. The upside is that I did find a great independent shop where I am still a customer.

Thanks to all for the input. I also suspected the starter motor becoming “heat-soaked” (I hadn’t heard that term before) and will be getting that looked into. I’ll post again later with results.

Okay, had the starter checked and replaced. Works like a charm now. Thanks again to all pointing me in the right direction. Have a great day.