Mysterious component - electrical fast idle maybe?

[rbgosling]

While tinkering with Lilith at the weekend, I came across a component that is clearly not currently functioning, and wondered what it is for and how it should work? Sorry, I'd have taken a photo, but the camera on my 'phone is buggered...

Anyway, it's mounted at the front top of the engine, and looks like a solenoid. Both wires were disconnected; whether they fell off of their own accord, or the PO had done it on purpose, who knows? By the looks of it, when activated it would push a lever that would open the throttle a bit - except it would push on an adjustment screw that was screwed all the way down, so wouldn't actually do anything (unless I re-adjusted the screw).

I theorised that this might be a device for opening the throttle when the choke was engaged - but a voltage test on the connecting cables remained at zero whether the choke was in or out (engine cold at the time). It would seem a good idea, since the engine always seems to struggle to keep running when cold, and I can't see any mechanical linkage giving extra throttle when the choke is pulled.

The Service Notes don't seem much help, the "Fuel System" chapter seems to give a detailed description of the working of the carbs but doesn't, as far as I can tell, mention this device.

In the Electrical section there is a Throttle Solenoid, that is activated either by a "Decell Relay" or the A.C. Compressor (not relevant, no A/C on Lilith), is this what I'm looking at?

Any pointers would be useful...

Thanks!

[amarshall]

Yup - that's the throttle jack solenoid. Designed to stop things closing too quickly, particularly when the extra load from the A/C compressor is on.

Detailed discussion here : http://www.lotusexcel.net/phpbb/viewtop ... ottle+jack

[Lotus-e-Clan]

It also helps clean-up over-run emissions.

All part of the development Lotus did to refine the 912 SE into a nice road engine. wink:

[rbgosling]

OK, thank you, that explains it all! I reconnected the wires, but since the adjustment screw is all the way in I doubt it'll have much effect.

So, is there anything that increases the throttle when you pull the choke out? As far as I could tell on a quick glance at the carbs, I couldn't see anything. Idle is fine when warm, but I often have to keep a bit of throttle on to stop it stalling when cold (a PITA when I have to get out of the car to close the garage door behind me!). I wonder if I could rig this device to do the trick for me...?

[AndyC]

The fuel enrichment mechanism in the carbs handles everything unlike the old SUs etc where they relied upon a external cam to open the throttle.

[Lotus-e-Clan]

When you pull the choke it raises the spring loaded plunger in the choke tower which lets in more air (a bit like throttle bypass function) plus extra fuel determined by the starter jet.

So no direct connection with the the throttle (it's a bypass system).

If pulling the choke fails to raise the revs from cold something is wrong obviously.

With more alcohol in modern fuels the risk will increase for water getting into the choke and or idle circuit, evaporating and leaving deposits which messes up the AFR (weaken most likely) or makes the choke plunger stick.

Also check freedom of accelerator levers (and state of the weak lever spring) below the carbs....