A loud clunk but no turn over

[jagnut66]

Hi, 

I have an issue with starting my freshly installed engine.

I have recharged the battery and let it sit on 'Maintaining' for quite a while to ensure it was fully charged.

Also I have had a look round but can't see anything I've rewired incorrectly.

However, when I try to start the car all I get is a loud clunk / click from the starter motor and the smell of it 'cooking'. Also (at the same time) the battery earth strap appears to be getting hot, although I disconnect the battery immediately after, to try to prevent any permanent damage there.

The obvious thing (to me at present anyway) is that the starter motor may have gone faulty, yet it was turning the old 1200 unit over okay, up until I took her off the road, as I was unable to select gears (which is a different saga in another post).

So is this possible or am I overlooking something? Has anyone had this issue before after stripping the engine out and replacing it? Also is a standard 1200 starter motor okay for a 1300 engine?

As always, thanks in advance for any help and advice given.

Best wishes,

Mike.

[PeteH]

Assuming the engine turns by hand,? The issue is most likely that the starter motor is having to work twice as hard cranking a newly rebuilt. and by definition possibly “tight” engine. “Adequate” for the old conditions does not automatically ensure it is up to the same task now? The earth strap getting hot is also likely to be a bad earth connection. Try again with a heavy booster cable from a clean bright spot on the starter.  Direct to the battery negative. I assume it is neg earth? Here.

Pete

[jagnut66]

Yes, the car is Negative earth. 

So a jump lead from a clean spot on the (for example) wall of the starter motor to the battery Negative might get it turning the engine over but if not then a fresh starter motor may be required?

The engine is clean and freshly painted, would that impede the motor body from earthing?

Also, would a high torque unit do a better job? I ask as I've never had one on any car I've owned, so have no experience of high torque units.

Best wishes,

Mike.

 

Edited July 8, 2023 by jagnut66

[dougbgt6]

Yes, what Peter said. I would connect jump leads to both sides of the battery and both sides of the starter motor.

Doug 

[jagnut66]

I have just tried my heavy duty jump lead from the Negative side of the battery to the body of the starter motor, no joy. Just clunk and smell, although not as strong now, me thinks the thing is fried.

Any thoughts on a high torque unit?

My engine is tight, she did turn (tightly) when freshly rebuilt but I haven't tried with her in the car, spark plugs back in their holes etc. I suspect it may need a bit of extra 'oomph' to get her turning.

Best wishes,

Mike.

[johny]

could try spinning without the plugs in? Also of course you havent tried a jump lead on the positive side which is where theres more likely to be a problem...

[Josef]

I’ve never tried a high torque unit. I figure the original style has been perfectly adequate for my cars for 50+ years so not worth spending extra on! Dave at the Spitfire Graveyard I’m sure will be able to sort you out with a decent replacement if it turns out to be needed for a fraction of a high torque unit.

[Stratton Jimmer]

A starter motor when not turning over is effectively a short circuit - super copper conductors connected between +ve and -ve. Only when it starts to rotate does it develop a 'back emf' which is the resistance that prevents it from cooking. If the motor can't turn, it will cook! I would advocate removing the starter motor and making sure that it spins over OK when disconnected from the starter ring. That's a good starting point in your diagnosis. If it does, then your next step is to make sure that the engine turns over freely. A newly refurbished 'tight' engine shouldn't appear that way to a starter motor that is designed to turn it over. If you have any doubts about your starter motor. get it seen to by ROTATING ELECTRICS of Birmingham. These guys are brilliant and relatively cheap. https://rotating-electrics.co.uk/ 

High Torque starter motors are good but a functional standard motor should be just as effective at turning over your engine. How many people have bought a High Torque motor believing it will cure all of their starting blues only to discover that it hasn't made any difference as the fault lies elsewhere?

[jagnut66]

All food for thought.

I will have to 'extract' my starter motor then. Not an enjoyable job due to the tight space it sits in with all my other ancillaries in the way. C'est la vie.

As an aside I found this on 'You Tube' about high torque units, very useful for anyone who hasn't fitted one before, as it takes you through the installation process. I found in clarified things.

Best wishes,

Mike.

 

[jagnut66]

Well the starter motor has now been removed and it tested okay.

It was then put back in but not wired up, as I used my heavy duty jump leads again, plugs out........

Back to just a clunk. 

So whilst the engine turned (with an extension bar I admit) when it was out of the car, it's obviously too tight for the standard starter motor to deal with.

For me, draining the engine, removing the rad, then the gearbox and all the ancillaries, before pulling the engine out again will be a last resort (too p****d off to even contemplate that at present).

I want to explore other options first, so I'm going to have a chat with a local engineer I know, during the week, to see what he might suggest.

Best wishes,

Mike.

[johny]

It is still possible that the starter motor isnt giving full starting torque even though it spins ok on no load. Theres a test in the workshop manual but of course it needs specialised equipment to do it🙁About the best you could do is try to find another starter to confirm the engine has a problem before going any further...

[Wagger]

Take all of the spark plugs out, engage neutral and rotate the engine using a spanner on the front pulley nut. If you are having to use an extender bar, something is wrong.

[johny]

yes my favourite possibility is crank bearing caps mixed up or on wrong way round😞 

[johny]

However, although not ideal, the majority of the bearings are accessible from under the car with the engine in place... 

[Wagger]

Assembling an engine is a precise procedure. I have witnessed engines delivered with standard shells after a re-ground crank. This resulted in oil pressure falling off drastically when hot, and loads of big end noise. The opposite should be impossible and would guarantee seizure.

I check all con-rods with their shells fitted on the appropriate crank before fitting crankshaft to block.

Then, I fit the crank and shells, torque up and check for free rotation.

Next, fit pistons with rings and assemble the big ends. Check for free rotation again.

Make sure the camshaft totates freely before fitting the chain.

Check that the tappets are free in the block. There were some oversize ones around in the 1990's.

Cars with starting handles made things easier when the engine was in the car.

 

[Pete Lewis]

8 hours ago, johny said:

favourite possibility is crank bearing caps mixed up or on wrong way round

there must be a good few Tee shirts for that one 

Pete

[jagnut66]

Well I've drained and removed the radiator, the fan and slackened off the fan belt, so that it's loose. Spark plugs out.

I attached my 38mm socket to the crankshaft nut and with my long reach ratchet tried to turn it over........

Guess what.

It turned.

A  bit stiff at first, I admit, but then it has been sat for a while. However, the more I turned it over the freer it got. I gave my arms quite a workout in the end, alternating between left and right, as one got tired. 

I then tried the starter motor, using my heavy duty jump leads, one to the body one to the power connection, both shielded by the way. 

The result?

A loud clunk from the motor and a puff of smoke at the positive terminal on the battery, as I quickly removed the lead from it.

(NB: Only the jump leads were used, it's live connection was removed and tucked safely out of the way and the car's + and - leads were left off.)

I have bought a (stated as being in good working order) second hand replacement.

I hope (with the aid of a little more hand cranking while I wait, to be sure I've done all I can to free things up and get the oil moving round things) it does the job.........

Keep your fingers crossed for me.

As an aside, I got a good whiff of petrol whilst I was turning it, so I guess that's the carb primed 😉.

Best wishes,

Mike.

 

Edited July 13, 2023 by jagnut66
additional text added