Curing a sticky starter solenoid

[KenMcCulloch]

The starter solenoid on my Yanmar 1GM10 has been intermittently sticking so we took it off and I took it to bits today. There's no obvious major gunging up or whatever; I cleaned the moving element of the solenoid and all the terminals etc, lightly greased the yoke and drive, and put it all back together. This is the first time I have stripped a starter that didn't have the old Bendix inertial thingy so I'm not quite sure what might cause the sticking solenoid. Is there anything else I should do?

 

[2Tizwoz]

Some earlier Bosch starter solenoids have a plastic former for the coil in which the solenoid plunger moves. Unfortunately, perhaps due to dampness they swell and the effect is as described. Later mdels have a different plastic which is not susceptible. Changing the solenoid requires a heavy soldering iron to dismantle the end cap which has the contacts internally and connection studs externally. If the contacts are poor it would be as well to change them whilst you have it in bits.

This all supposes that yours is a Bosch starter.

 

[huldah]

Are you sure that the problem is due to the solenoid?

My starter may be different to yours. I have had problems with the relay that drives the solenoid. In my case, the current passed through the centre of the relay. High resistance, caused by corrosion in the riveted area, restricted current flow.

The solenoid must do two things. Engage the starter pinion, and then make a contact, to switch on the starter motor. There is often an adjustment on top of the starter motor. This must be adjusted so that the pinion is almost fully engaged, and at the same time the contacts meet. If the pinion is against it's stop, there may not be enough movement for the contacts to engage.

Usually, this is adjusted by slackening a nut and turning an eccentric pin.

I have seen a rather risky test for this. The engineer slammed a spanner across the solenoid. The motor stared without engaging the pinion, proving the cause of the fault. However, the shower of sparks and damaged spanner encourages me to avoid such tests! Perhaps a meter would be safer. (The meter should read zero, if the contact is made).

It could, of course, be a sticking brush. In this case the meter should read zero, but 12 volts if taken to earth, while the starter button is engaged.

Philip

 

[KenMcCulloch]

[ QUOTE ]
Are you sure that the problem is due to the solenoid?


[/ QUOTE ]
Well, on the basis that the last time the fault showed was when the boat had been left for nearly 3 weeks, yes, fairly sure. Pressing the starter button produced no effect, not even a click. 'Percussive maintenance' (a sharp tap on the solenoid with a handy sized spanner) and a second attempt produced a fully functioning starter.

 

[William_H]

I tend to agree with Huldah in that if you get power to the solenoid you usually get some sort of click action.

Incidentally I disagree with Huldah in that a multimeter will not usefully tell you if the contacts are making properly. The resistance required of the contacts for good stater operation will be less than .002 of an ohm. Most multimeters are useless below one ohm. So the spanner test is actually usefull. Perhaps 2 heavy wires connected properly to the solenoid terminals and shorted together in a safe place or with another purpose built solenoid would be less scary.

Anyway back to t he original post. Coingratulations on pulling the solenoid apart and cleaning it. I always admire/ encourage DIY.

As suggested you should provide another wire to the operating terminal of the solenoid. I don't know if it needs + or an earth to activate the solenoid. It needs an earth if the other side of the coil goes to the battery connected lug of the contacts. Anyway see if an alternative circuit to your normal start switch will bypass the fault.

Sometimes the circuit uses another relay to carry the high (relatively) current of the solenoid coil other times the current goes through the start switch. You coulld fit a relay as a way of getting better power to the coil while coping wityh a poor start switch.
good luck olewill

 

[Taffy]

Hi,

I saw this problem this summer and took the solenoid apart. Finaly traced it to a loose earth/negative connection on the battery.
Have you checked your earth connection to the engine ?

 

[Guest]

We had an old TK Bedford 330 truck that we used to short the solenoid on ... if you are positive and do it with force - the sparks are a lot less ... I reckon we ruined 2 or 3 screwdrivers before our mechanic fitted replacement ...