Starter Driving Me Crazy

[JGrad]

H Everyone. Hope I'm in the right place for some advice.

Could someone offer advice with my starter issue, please.

I have inherited a Marshall Tractor which apparently started fine a few years ago.
Now when trying to start it, there's a massive clunk from the starter with battery instantly drained.

I took the starter off and connected a 12v battery to + and - to the starter casing
Shorted out switch connection to positive and saw the bendix fly forward with a clunk, motor does not turn.
So based on everything I see on YouTube, figured the solenoid is OK but there's a problem with the starter.
Then connected + directly to the starter, bypassing the solenoid, and the starter motor spins correctly.
I'm at a loss and spares for this old Magneti Marelli part might be very expensive. I believe they were made by Ferrari or something

Any ideas would be appreciated.
Many Thanks

[E-bmw]

So you have just proven your starter seems to be ok, so change the battery.

[JGrad]

And I thought I had covered everything that I'd done in my first post!
The battery was fully charged and tested, just in case
Thanks for the reply....

[Elliot2000]

Can you manually turn over the engine at all? It may be seized

[finlo]

Elliot2000 said:

Can you manually turn over the engine at all? It may be seized

My thoughts exactly.

[GreenV8S]

A seized engine does seem the most likely suggestion. If you have convenient access, a squirt of light oil down each bore and time for that to soak between the bore and piston would help free the engine up. I suggest you resist the temptation to apply brute force to turn the engine over, but you should be able to nudge it over with a bar on the front pulley.

[E-bmw]

JGrad said:

And I thought I had covered everything that I'd done in my first post!
The battery was fully charged and tested, just in case
Thanks for the reply....

Tested how exactly?

[JGrad]

Many thank for the replies.

The starter is actually on the bench so I don't think that the engine being seized can be the problem.
(Scared the life out if me though so I checked anyway with a screwdriver on the flywheel. Thankfully not seized :-) )
Sorry for the late reply - it seems the forum was closed to new users due to abuse some where.

[GreenV8S]

Sounds like there may be a short within the solenoid, then. Some solenoids use two windings to close the solenoid and just one to keep it closed - so the solenoid switches itself as well as switching the motor iyswim. Maybe there is an internal short there. The internals are probably pretty basic and I expect a competent electrician would be able to find the fault if they dismantled it.

[JGrad]

Also, the battery is the one out of my car which is six months old. When it first happened, I checked the voltage and had it on charge overnight, just in case. Although its a tractor, its a two cylinder compact and so doesn't require a large battery.

[JGrad]

Thanks for the replies. The solenoid suggestion definitely seems to fit the symptoms. If they can test for that, I think the next step should be to take it somewhere and try and get it tested.

[E-bmw]

JGrad said:

I checked the voltage and had it on charge overnight, just in case.

I don't mean to keep pushing, but when you tested it what exact voltage did you get?

It should be between 12.6 & 12.8 volts for a freshly charged good battery.

Every 0.1 volt less than 12.6 is around 20% charge drop. 12.1 or under is basically completely flat.

[JGrad]

No problem, thanks for taking the interest. To be honest I can't remember what exactly the voltage was, but it was twelve something so I didn't think any more of it. It's just that I'm testing on the bench now so didn't think it was that critical. Do you think that would make a difference in the solenoid action? Bearing I mind that the motor does turn when bypassing the solenoid?

[GreenV8S]

JGrad said:

No problem, thanks for taking the interest. To be honest I can't remember what exactly the voltage was, but it was twelve something so I didn't think any more of it. It's just that I'm testing on the bench now so didn't think it was that critical. Do you think that would make a difference in the solenoid action? Bearing I mind that the motor does turn when bypassing the solenoid?

In your original post you said 'battery instantly drained'.

Do you mean the battery voltage dipped way below 12V? If so, if the solenoid/starter is causing that you'll have been drawing huge current from the battery. On the other hand if you're only drawing tens of amps and the battery voltage is plummeting, that suggests a battery problem. If think this is what E-bmw is referring to.

[paintman]

JGrad said:

Thanks for the replies. The solenoid suggestion definitely seems to fit the symptoms. If they can test for that, I think the next step should be to take it somewhere and try and get it tested.

If you put where you are you might get some suggestions.
For those in the Leicester area I've used these for years for car alternator & starter motor repairs:
www.facebook.com/Greens-Starter-Motors-Alternators...

[JGrad]

Yes, the battery seemed to lose all power. Ignition lights wouldn't even come on. Took a few minutes to come back on

I'm in the very north of Scotland so no specialists close to me.

[GreenV8S]

JGrad said:

Yes, the battery seemed to lose all power. Ignition lights wouldn't even come on. Took a few minutes to come back on

I'm in the very north of Scotland so no specialists close to me.

Try it with a known good battery.

[E-bmw]

JGrad said:

Yes, the battery seemed to lose all power. Ignition lights wouldn't even come on. Took a few minutes to come back on

Which is exactly why I was pushing you, it seems your battery is stuffed as I said originally.

Lots think when you see 12v on a 12v battery that it is good, anything under 12.1v is completely flat as far as practicalities are concerned.

[JGrad]

Thanks everyone for the replies.

I tested the battery again, it read 12.73 volts before trying the starter multiple times and 12.53 immediately after.
The battery is six month old and is the battery from my car.
The battery drained when the starter was still attached to the engine but now that I have the battery on the bench it is not draining.

To try another test that I saw on YouTube, I connected a + connection from the battery to the solenoid post and a - connection to the body of the starter.
I then connected a test lead between the spade connection on the solenoid to the + connection on the solenoid. The suggestion was that this voltage should be 0v once the solenoid has fired and the starter motor is turning. That didn't happen. Before I could measure the voltage, the test lead started to melt.

It seemed to me that the solenoid was continually activated and that's the reason why the Bendix stays forward, Am I right in assuming that the solenoid is supposed to switch off at that point?

[GreenV8S]

No, the solenoid stays activated while the starter is running. However, there are usually two coils in the solenoid: 'pull' and 'hold'.

The pull circuit does the main work of mechanically pulling the solenoid into the operating position i.e. moving the drive gear into engagement and closing the contacts to power the motor. This circuit is in series with the starter motor so that when the contacts are closed this circuit is effectively powered off.

The hold circuit is between the supply and ground and holds the solenoid in the operating position.

These two circuits can carry tens of amps and could easily overload a light gauge wire. If you were using heavy gauge wire, this overload is consistent with a short circuit within the solenoid that we have been speculating about.

What's the resistance between the solenoid terminal that receives cranking power from the ignition switch, and ground? On a normal light vehicle starter motor I'd expect to see several tenths of an ohm here.

Edited by GreenV8S on Saturday 20th July 16:23

Edited by GreenV8S on Saturday 20th July 17:00