Starter labours when the car is warmed up

[Jimb]

Hi guys,
When I first start the car the starter turns over great, but if I shut the car off after a run then go to start it agin the starter really labours. It turns over slowly before it fires.
Any ideas?
Jim

[2ndwind]

I'm wondering if you have a weak battery or poorly charging alternator . Here's my thinking: battery sits overnight with no load other than the clock, starts ok in a.m. Driving along, battery is being drained by engine and car functions, very little available to restart.

I can't think of how something mechanical would change causing "back pressure" after warming. Can a clogging catalytic converter do this?

[Jimb]

Yes after giving more thought I would agree with you. I've just checked the terminal on the battery and they were a bit loose so I'll start with that.
Thanks,
Jim

[So Cal Mark]

voltage drops are a huge problem. Supplying low voltage over a long period will ruin a starter. Starters draw more amperage when hot, so hot cranking can be an issue when a starter is failing

[Jimb]

voltage drops are a huge problem. Supplying low voltage over a long period will ruin a starter. Starters draw more amperage when hot, so hot cranking can be an issue when a starter is failing

Yikes!, So you're saying it's time for a starter rebuild?
Damn! I wish I had known that when I had the engine out.
Jim

[So Cal Mark]

very possible, but first fix those poor connections. No connection should have more than .1 voltage drop

[stpher]

Could also be a problem with the bushings in the starter drive end getting hot and slightly expanding causing too much drag on the starter but, I agree , with the connections. Make sure those are all good, check the main power wire and the one coming from the ign. switch for both corossion and overheating. The corrosion usually shows up as the copper core wires go bluish or for overheating the cable gets blackened, either one can be fixed by ctting back the wire ( if you have enough of it ) to where the inner wire core is nice and clean. Put new connectore on the ends.

Good luck

Thanks, Rick

[76was124]

Starters draw more amperage when hot,

Well the electrical geek in me is now confused so pardon my slightly irrelevant question.

Does the starter really draw more current when hot, or does it just become less efficient (weaker) and get over heated?

I am just thinking if copper resistance raises with temperature, wouldn't less current flow due to more voltage drop across the copper, thus causing more heating and weaker magnet field? Or is it that it's something mechanically happening, or because it's weaker and resulting in a locked rotor (heavy load) effect that makes the starter effectively a dead short. Which then drives the current through the roof and will quickly make it toast?

[So Cal Mark]

this usually occurs when the bushings in the starter are worn, letting the armature contact the field windings. With the various parts experiencing expansion due to heat, the armature can get stuck to the windings. This is why rapping on the starter while cranking will sometimes cause it work (temporarily).

[76was124]

Thanks Mark,I can sleep now:)