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Chaps,

I've been trying to start my car after winter hibernation but having difficulty getting it to spin. The engine only turns over quite slowly - not quick enough to catch. The battery had seen better days so I spent ?200 on a new one, charged it up but the problem still remains.

Over winter, I have drained the water to remove the water jacket plate which I've painted and refitted with a new gasket. I've had the radiator and distributor off but I don't see how these could be the problem - the engine turns but not very quickly and there's no untoward noises.

All connections to battery and starter are good

I thought maybe the water pump had seized as it has been dry all winter but I'd expect the belts to slip if this was the case

Any ideas what could be the problem?

Assuming it's not a mechanical or electrical problem of some sort, what weight is the crankcase oil and how cold is the temperature? With heavier (summer) oils in cold temperatures, faster cranking can be obtained by using a dipstick heater to warm the oil first. Dipstick heaters used to be a cheap purchase at better auto parts stores, not sure anymore.

Hi Dave,

No the oil will be fine - the garage is heated and in any case we finally have some spring temperatures: 7 degrees C

I'm beginning to think its a case of bad connections / earths. I did disconnect the starter motor so I'll double check that the connection is good.

I've removed the starter motor and tested it on the floor direct from the battery.

It turns but starts slow and then speeds up. Its not really fast - difficult to estimate rpm but I would have thought it should have leapt in the air when powered up without any load.

Can anyone say how it should be?

I worked out that the starter motor should spin at about 2500rpm in order to turn the engine at, say, 250rpm - enough for it to start.

Well I've checked the starter motor again on the floor and I'd say is it spinning at about 300-500 rpm, so there's my problem.

Now I'm not sure if its an issue with the starter motor itself or the new battery I just bought, although the old battery was just about the same.

The motor turns freely enough and all 4 brushes have meat left on them and they seat on the commutator nicely with pressure from the springs.

A thought on the battery though. The book says that the 745 should have a 160Ah battery. The one I've fitted is 120Ah (its the biggest one that would fit in the box!)

The capacity in Amp-hours should be irrelevant to the cranking power. Thing is, with these traditional 6volt batteries, no cranking power rating is given.

Any thoughts?

I'm not particulary familiar with the starter on a 745 but typically the Owen-Dyneto starters on the larger Packard in-line 8s had no-load speeds of 6000 rpm, drawing 60 amps at 5 volts. At lockup they should draw about 600 amps.

Kts68,

Had a similar problem with a car that was stored over the winter wouldn't turn over come spring. Finally traced it down to a film of corrosion on the starter commutator. The commutator looked fine, dull copper color, but the thin film of corrosion / oxide was enough to insulate the brushes. I pulled the brushes out, lightly sanded them with 400 grit sand paper. Did the same to the starter commutator. The starter fired right up after this.

Some handy reference info attached.

Regards,

Dave

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Thanks Gents,

I did sand the surfaces of the brushes as they looked a bit dull (they are copper which seems unusual to me).

I also cleaned the commutator with alcohol but it looks to be clean. I also carefully removed copper residue from between the strips. I was reluctant to start sanding the commutator but I think I'll go back and do this gently. Maybe the alcohol wouldn't have cleaned off any residue.

To be fair, once I'd cleaned the whole starter motor and tried it with beefier jump leads it did spin faster but still not what I'd expect.

Be sure that any wire terminals inside and outside the starter are SCRAPED with a knife blade or coarse file to shiny virgin bare metal. Put a lite film of white grease or silicone on them.

kts68: The brushes are not copper but are either copper-impregnated carbon or copper flash-plated due to the very high current needs. Question - do the brushes arc signficantly when you power the starter? If so I'd examine the commutator to see if the mica separators between the conductive segments are properly recessed below the copper conductors. If not, to get proper brush contact you need to cut the mica back so it is recessed slightly. This is shown in most any text on starter or generator service and is a standard process when servicing a commutator. There are special tools for it but a piece of broken hack saw blade works as well as anything; then finish up by polishing the commutator and perhaps refacing the brushes so they give full contact.