New battery, but won't turn over when hot

[BrianK 25]

The last couple times I've driven the car, after a short drive, the car won't start.  It doesn't even turn over - you hear the click when you turn the key, but the starter doesn't turn. It starts just fine when cold.

The last time this happened, I waited until the end of the day to return to the car, jump-started it, and happily drove home.

Not knowing the history of the battery, I replaced it with a brand new one yesterday.

Today, after my short drive (15-20 minutes, mostly in traffic), after parking and returning to the car, it again failed to start.  I called a friend to come give me a jump-start (who arrived about 20 minutes later - engine still warm, ambient temps still high), but even with the jump, it's not starting.  Always the same symptom - click but no start - much like the battery was dead.

From my quick research, this sounds like either a problem with the starter or problem with wiring to the starter. It could also be that the starter gears were in perfectly wrong alignment with the flywheel, so I rocked the car back and forth while in gear to see if that would "free" it...  No help.

Any thoughts on the issue - does it sound like starter? More importantly, recommended test procedures to help me track down the problem?

I'll be returning to the car after it cools down tonight, in hopes that it will accept the jump-start. I'll also accept tips on getting the thing started just so I can get it back home without a tow truck.

FWIW, the battery I'm using has 750/660 cranking amps (normal/cold).

 

Edited to add: this is a '74 Elite

Edited August 16 by BrianK

[tom kilner 110]

Sounds like a classic starter solenoid, although it could be dodgy wiring.

It could even be a bad earth if the battery negative connection is poor. the starter is the highest load on the system,  so the first to fail.

Another thing to check is there's still voltage in the battery - it could be going flat due to failing alternator or some unknown load. Turning on the headlights gives an idea if you don't have a multimeter.

If it's not the battery...

You might find if you bang the starter with something, it works, as yours is borderline.

With the ignition off : It would be worth jumping power straight on to the starter live terminal on the solenoid to see if the motor works ok with direct power  - that's the large terminal on the solenoid nearest the motor body. The motor should spin but won't engage with the engine.

 

Also a positive voltage applied to the small spade terminal should operate the solenoid with a heavy clunk.

 

The other large terminal (outer with yellow connector in the photo) is the positive to the solenoid (It's  a mechanical switch). Turning on the ignition should live that up,  then a positive to the small spade should then close the switch, and then power the starter, and crank the car. this can be done with a spanner off the outer terminal.  Turning the ignition key to the start position applies live to the spade - the fact your car clunks at this point means this bit is working.

Be sure all parts of clothing, anatomy etc are clear of any moving engine parts. It's also important there's no petrol or vapour around as testing will produce large sparks.

A fire extinguisher and a helper are a good idea.

The starter motor is easy to remove - you can have a go at dismantling  and cleaning the solenoid assembly as it might just be dirty - you can also file the contact  plates flat again,  but ultimately you'll need a new solenoid,  easiest you just replace the starter as a professional repair will probably cost you more.

If you need to start it tonight and it's not a flat battery,  you can jump the solenoid switch with a spanner. Turning the ignition gives you the clunk of the solenoid engaging the motor with the engine - if you then put a spanner across the two solenoid terminals, you can supply voltage to the starter directly bypassing the solenoid switch. It could also be done with a jump lead to that inner terminal,  allowing the"electrician" to live the motor up at a safe ish distance by touching the other end on the jump battery. Hard to get a firm connection with a clip though - some cabling might be required.

See warning above though. It might just be easier and safer to bump start the car.

 

[oilmagnet477 602 2 Vehicles]

Tom - spot on I reckon. Had EXACTLY the same problem with an old ride on mower (no offence intended lol). Could start with a spanner (Sparky!!). Put in new solenoid and problem solved!

[tom kilner 110]

 well interestingly I have 2 starter motors as my original solenoid is falling apart.

The "jump the solenoid" trick spins the motors:

But the "throw the starter  pinion"

Works on one without a live supply to the solenoid,  but not the other.

The spanner methods shown should work with live to the yellow tab...

Assuming a decent earth to the motor body.

Doing this on the bench you have to watch out for the starter jumping right off the surface and landing on your feet.

[ramjet 912]

My bet is on the solenoid as well, or a dodgy earth that faults when things are hot.

If the starter will turn the engine when it is cold, that rules out the motor itself and the gear throwing into the flywheel.

Only leaves the two things up the top as the culprits.

[BrianK 25]

Thanks for the replies, all. Tom, I really appreciate the time taken to get pictures.

For what it's worth, I was able to jump-start the car later in the evening after ambient temps dropped.  I did, previously, attempt to whack the starter, with no luck (admittedly, I only had a small spanner on hand - so not much of a whack)

I'll do some testing based on these suggestions, but it's sounding like a new starter is in order.

Thanks again.