Looking for a picture or description how the thermostat is connected to the throttle body of a ljet motor (maybe the same a djet setup). What other components are involved in the warm-up circuit of a ljet motor?
Thanks...if you got a picture, all the better.
Mark

Mark; Oh boy. the cold start/warm up of the L-jet is way more complex than what you are asking. All the links to the info are on this site. read up/try to understand how it works. then maybe we can help diagnose.
Randy

Oh, it's easy. The throttle body is bolted to the engine, and so is all of the warm-up stuff. That's the only connection between them.


....Oh, a real answer? OK, let me try...

There is the cold-start valve. It is, contrary to what lots of references will tell you, not a part of the warm-up stuff at all. It is merely to help the engine get some extra fuel while the starter is cranking so it can light off easier. It is run by the starter circuit and the thermo-switch (or thermo-time switch on the 1975 1.8s).

There is the head temp sensor, in the head near the #3 spark plug. It tells the ECU to make the mixture richer when the head is colder.

Finally, there is the Auxiliary Air Regulator. This is what keeps the engine from stalling at idle when it is cold. It acts as a bypass to the throttle, in much the same way that the idle passages in the throttle body do. But this is a separate part, up to the left-front (I think???) of the manifold. It has one vacuum hose that connects to the manifold, "downstream" of the throttle valve, and one that connects to the intake boot, "upstream" of the throttle valve. When the AAR is cold, it lets lots of air go through it, bypassing the closed throttle. When the AAR warms up (and there is a heating element in it to make sure it warms up), it closes so that it doesn't let any air go from upstream to downstream.

That's pretty much it. I don't think the 74 1.8 has an intake air temp sensor (the 75 does), but that isn't exactly part of the engine warm-up part.


OK, one other thing that has nothing to do with the fuel injection: There is a thermostat on the bottom left side of the engine, shaped like an accordion. When it is cold, it pulls on the wire attached to it, which pulls the flaps inside of the engine tin to the "warm this engine up please" position. When the t-stat warms up, it expands, and the spring on the flaps cross-shaft pulls the flaps into the "maximum cooling now" position.

And the latter system is what we usually mean when we talk about a thermostat in a 914. But it's not fuel injection related, other than being bolted onto the same engine as the FI system.

--DD

Dave & Randy,
Thank you for your comments and guidance. I am fairly familar with the function of many of the components mentioned above, but let me provide a bit more context for my question.

I have a 75 1.8 with an automatic which runs wonderfully and does seem to run through a warm-up cycle, but then again the weather is pretty warm now in CA. It seems it should have a faster idle than it does when the engine is "cold."

On the throttle body there is a lever on the top that is not connected to anything. The accelerator cable is connected and a "kickdown" for the automatic is also connected. It's been years since I've seen a stock 1.8 throttle body setup, so I'm trying to figure out if that top lever should be connected to the thrermostat coil, or what does it connect to.
Mark

I believe the top lever on the TB is for attaching the "emergency" return spring

If you don't get a rise in RPMs at start up; pull the AAR and see if it's working. While cool, the orofice ( hole ) in the AAR is approc 1/3 open. Hook it up to a 12volt source and watch it close. Mine take an average of 1 1/2 minutes to close from ambient temp. If you put the AAR in the refrigerator ( or freezer ), the orofice will open even wider as the temp drops. WD40 is a safe lubricant for it

I get a a rise in RPMS to about 1600 until the AAR closes, then the drop back to 900 as the AAR closes.

Good thing is that it's easy to test.