Early Jaguar Auto Enrichment Device

How did you get it to make a nice hefty click off the car? And they don't normally go soft, but you may need to move it slightly closer to get enough initial pull in.

They're very simple devices - see here for diagram:

I took the solenoid part off the enrichment assembly and supplied it with

12v - the iron plunger/spring/disc retracted quickly and with a nice hefty click.

The winding part of the solenoid can only be in one position so there's no adjustment in relation to the plunger.

Logic would suggest two possibilities.

1) The disc is no longer firmly attached to the solenoid because summat's broken inside so manifold depression stops the disc moving when the engine's running.

2) The solenoid has lost its mojo.

I suggest the former. Strip it down and have a look.

I've already stripped it - the disc is still firmly attached to the plunger mechanism.

Looking mojo-ish...

What is the solenoid resistance?

Don't know - forgot to check it. What should I expect?

At a guess, about 4-10 Ohms, but that's a guess. If it makes a loud clunk when off the car then I'd still bet on either the contacts to the solenoid being crap or the live feed.

Hmm I'm wondering if the whole solenoid mechanism should be airtight - that way it wouldn't matter how low the pressure was on one side of the disc, it should have equal pressure on both sides iyswim? Does the coil etc. have a perished rubber seal perhaps?

It makes a loud clunk when it's on the car too - just not when the engine's running.

I'll stick a meter on it tomorrow.

No. At their fundamental they are nothing but a coil of wire and a lump of iron free to move around in the middle. So, nothing to "go off".

Mechanically though a different matter entirely. Gunge, s**te, rust, poor linkages and all that will make them sticky which may or may not be your problem.

Failure of the insulation between layers of the coil can make the solenoid much weaker.

Indeed, as can failure of the varnish between the layers of a laminated core, although car stuff isn't always that sophisticated.

Chris

Solenoids are generally air cored and have few layers.

Yep, certainly in car-type sizes; I've mostly dealt with ones several orders of magnitude larger in industrial situations, so very different.

I was really just agreeing with your statement that a solenoid can fail in a way that allows it to operate, but weakly.

Chris

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "sweller" saying something like:

Yes, they do. Especially ones of that era.

Duncan Wood submitted this idea :

At the back of my memory, I seem to recall they used to fit a manual switch to power the solenoid, bypassing the thermal switch.

steve auvache used his keyboard to write :

I also wonder if something might have become magnetised, which could be countering the solenoids action?

It'd have to be very magnetised :-) I note that Bentley still sell the original service manual , which probably answers the question of what it's resistance should be.

I have the factory manuals for the XJ6, and early cars appear to have the same unit. No resistance given.