Solenoid

[sp250boy]

Hello Gents,
need some guidance..

If I press the manual button on the solenoid the engine turns.. When I turn the key and press the solenoid on the dash nothing happens. I can not see a positive earth strap to the engine but the positive earth is connected to the chassis and then gearbox. I was going to add another earth strap to the engine, but run out of time this evening.

The other thing I find strange but don't have a circuit diagram to check is the wire that comes from solenoid starter switch that go to the starter button on the dashboard. The wire seems to be connected to the solenoid body itself, is this correct?

Thanks for any help and guidance...

[Simon Hyslop]

Hello, do I remember correctly that you have a 38 or 39 11? If so, I think these have a solenoid numbered 760039. This is a small electromagnetic switch mounted on the top of the starter, a bit like the shape of a small round junction box mounted on its side held on by two set screws into the starter case? The contact point for the wire from your starter push should be an insulated terminal, not the body of the unit itself. If it is connected to the body, you should be seeing a good going short circuit displayed on the ammeter. These old solenoids can give trouble. However, with a small bit of ingenuity it should be possible to substitute a more modern one if there is something amiss with yours. Perhaps if you could take a photo of it we can see to be sure. My vagueness is because the Lucas catalogue I have stops at 1938 but it may be that the same units were fitted in 1939 but a lot of makes had gone on to the end mounted solenoid that carried on into the early post war years.

[sp250boy]

Hi Simon,
attached pictures..

[HenryC]

The wire from the starter button on the dash should be attached to the small terminal with the two nuts, see your first photo. This provides the power (negative) to energise the solenoid when the starter button is pushed. The earth (positive) is through the casing when it is bolted to the bulkhead.

The two large terminals are for the supply from the battery and the feed to the starter motor. It doesn't matter which is which. There may be other wires connected to the battery side, leading to the regulator and other items.

If you have converted to negative earth, it still is wired/works exactly the same.

Hope this helps

[Simon Hyslop]

I see you have a meter. Excellent ! Connect a battery earth to the metal mounting lug, a live to the small terminal and measure with the meter for continuity between the two large terminals. If none, the solenoid is probably past it . If there is continuity, I'd suspect there isn't a good earth as Henry has alluded to on the car itself. If there is an earth, check for 12 volts at the solenoid end of the wire from the starter push when it is pressed.

Should you need a new solenoid, one of these should fit (or be able to be made to fit...) :

https://www.ebay.co.uk/itm/Push-button- ... Sw7VRgOBCs

There are cheaper solenoids available but they tend not to have the push button start on the unit itself.

[sp250boy]

Gents,
thank you for your help..

Three terminals on the solenoid...small terminal (brown) goes to the button on the dash
# 1Large terminal goes to starter
#2 Large terminal goes to battery negative.

The solenoid/body is mounted to plywood and therefore, not connected to positive earth. I wonder what could be wrong here

[HenryC]

I wonder!

[sp250boy]

Hi Simon,
thanks for link for the solenoid.

I have bought one just incase and will fit it over the weekend.

[simonp]

I prefer the old type solenoid which is extremely useful when tuning the engine, setting points and valve clearances etc.

SimonP