Starter motor, occasional problem

[Gareth E]

9 times out of 10 my starter motor turns and the engine starts, no problem. The tenth time (or so) I get the familiar clicking sound of the starter motor jamming. Or at least, that's what it sounds like. I replaced the motor last year as the previous one was knackered (constant clicking sound). 

 

Before I consider taking the motor off to have it fixed is it possible that this could be caused by a poor connection somewhere? If so, any suggestions where I should check?

 

Thanks.

[Arthur Marshall]

Mine was unreliable because of a dodgy earth lead. Covered in oil and muck.  Moved it to a different bit of the engine mountings and no further problem.

[Ian F B]

I agree, dodgy connections are the first thing to check,pay particular attention to the crimped connections on the ends as these can be a problem especially as they age. ?

[zenataomm]

A loose or dry connection will create a drop in black magic getting to your starter. As it uses between 50 - 200 amps to turn your engine over it needs all it can get.

Clearly that amount of juice can't be allowed to pass through your ignition switch as it would burn the contacts and melt your cuff links. 

So your ignition merely powers up a beefy solenoid that can cope with all those sparks, however if you have a puny connection somewhere (usually the earth) the starter doesn't do more than twitch.

What you hear is the solenoid clicking.

[David Mack]

And a bad electrical connection may well have been the cause of the problems with your previous starter motor.

[Jen-in-Wellies]

Once you have checked and cleaned up all the big electrical cables, including the earth lead back from the engine to the start battery, the next most likely cause is the contacts inside the solonoid itself. These make and break the large currents used by the motor and the sparks from this will pit and erode the contacts over time. Brushes on the motor will also wear and pit and are another possible cause. Most towns of an appreciable size should have a firm that overhauls and repairs starter motors and should be able to help.

 

Jen

[Tony Brooks]

If by "constant clicking" you mean what is often called machine gunning then as long as you are sure your battery is well charged and in good condition the most likely cause, as already said, is a poor connection. I would suggest that you first clean up the clamps and posts on the start battery to bright metal. Again, subject to that incident being machine gunning the problem is far less likely to be related to the starter itself and more likely to be related to a low voltage. If it did not machine gun then measure the voltage on the small single solenoid terminal when starting. If its less than (say) 10 volts then consider the connections and cable size between ignition switch and solenoid, including the large multi-plug that is in most bat''s main engine wiring loom. If all that looks OK yet you still ave less than 10 volts then it could be a worn ignition switch.

 

 

 

 

 

[Boater Sam]

Loom multiplug, always suspect.

[dor]

On Vetus engines, and maybe others, there is a relay that operates the starter solenoid.  IF the contacts on this are poor, either external spade terminals or the internal contacts, then you will get the clicking sound you describe.  The relay(and one for the heaters) is in a black box on the back of the engine.  Giving this a clout and/or cleaning the contacts will fix it.  You can get a replacement relay in Halfords for a fraction of the price of a Vetus-branded one.

[Onewheeler]

If dodgy contacts in the starter solenoid it may be easy to dismantle it and apply a file to them (I can only speak for having done it on a BMC engine). H&S warning: disconnect power first!!

 

Martin/

[Tony Brooks]

The OP says new starter last year so although not impossibly, especially if the boat as a lot of water & oil in the engine tray, that diagnosis is less likely than other things that have been mentioned.

[Gareth E]

For now I've re done all the connections, cleaned etc. It is a Vetus engine, I wondered what the little black box on the back of the engine was, now I know! 

[Tony Brooks]

4 hours ago, Gareth E said:

For now I've re done all the connections, cleaned etc. It is a Vetus engine, I wondered what the little black box on the back of the engine was, now I know! 

If one little black box feeds the starter solenoid it is very unlikely to be any thing to do with the ignition switch or cable.

[Gareth E]

1 hour ago, Tony Brooks said:

If one little black box feeds the starter solenoid it is very unlikely to be any thing to do with the ignition switch or cable.

Any thoughts what it might be? It's similar to the split charge relay near the batteries.

[dor]

Inside the black box on the back of the engine are two standard relays.  These are smaller black boxes about 30mm cube.   I can't remember offhand which one is which, but one has large spade terminals the other standard small ones. One operates the starter solenoid the other is for the heaters.  Pull the relay off - just lift upwards - and make sure the contacts are clean.  When you reinsert it, make sure the spade connectors fit and are not pushed down without engaging.  Just removing the relay and reinserting it is usually enough to clean the contacts, but it is possible that the relay itself is failing.   The intermittent nature of your problem as initially described is exactly what you get if these relays are not working properly.

I wouldn't bother replacing the outer black box - mine came off years ago!  It makes it easier to give the relay a tap if you get the problem reoccuring.  Relays are standard automotive relays.  Get them from Halfords or ebay rather than pay Vetus prices.  Make sure it has the correct size spade terminals.

 

Just dug out my notes:

 

Edited August 19, 2018 by dor

[Momac]

Different engine but the same issue on my last boat was a loose connector on the stater relay - so keep looking for it.

[Tony Brooks]

9 hours ago, Gareth E said:

Any thoughts what it might be? It's similar to the split charge relay near the batteries.

If you have a small relay near the batteries its anyone's guess what the boat fitter did. If its a twin alternator boat it MIGHT be a relay to energise the second alternator but I would expect that to be close to the instrument panel to save wiring.

 

It MIGHT be a relay for the glow plugs.

 

It MIGHT be a relay to energise the starter solenoid as has been discussed.

 

If you mean does it look like a split charge relay then usually yes but smaller but with all blade terminals.

 

I simply do not know. You need to trace the wires that are on it. and one should go to what its controlling. One  will be energising it, one a negative, and one a positive supply. If two cables are a bit thicker than the others then one is the pos supply and you are interested in where the other ends up.

 

Dor is 100% right about avoiding Vetus prices but there are a few different terminal arrangements so make sure any new relay has the same number of terminals and when you look at the base or the image printed on the case the numbers by each terminal are the same and in the same place relative to the others. You do not need a relay with a diode in side it although getting one will not hurt  except the diode might just blow when you use the rely but it should then make no difference.