warm up regulator //Why?

[mr.flat6]

1981 911SC 104,000 Miles

I'm suspecting a warm up regulator problem.
What does this regulator, regulate?
Air or fuel?
If the CIS has constant fuel pressure to all 6 injectors, why the need for a warm up regulator, etc.
Anyone have a great technical answer to theses questions?
I'd appreciate it.
Tx!john

[jmohn]

It "richens" the mixture when the engine is cold and when you accelerate (sort of acts like both the choke and the accelerator pump on a carborated engine).

Jerry M
'78 SC

[dougcl]

The WUR controls fuel pressure. When the WUR opens, fuel in the control pressure circuit bleeds back to the fuel tank, lowering the control pressure in the fuel distributor. The control pressure acts against the sensor plate. The higher the control pressure, the less the sensor plate will deflect for a given air flow (leaner). The opening and closing of the WUR is determined by engine temperature (and manifold vacuum.) When the engine is cold, the WUR is open. When the engine is warm, the WUR is closed.

How the injectors deliver a varying amount of fuel with constant pressure escapes me. Perhaps someone can explain this.

Doug
75 911S

[MotoSook]

Why do you suspect the WUR? For good trouble shooting of the fuel delivery system, you have to have a CIS (Fuel Pressure) tester. Get one from JC WHitney for less than 70 dollars. That's less thatn one hour's labor at the dealer! AGAIN I ASK, why doesn't Wayne have that on Pelican for the same price? JC must make money on it, Why not Pelican, at the price? Actually, if Wayne was to start selling them, I'll fab some up. Having fooled around with fittings on the pipeline, I'm sure I can fab one up for cheap...just never did it as doing just one or two is not cost effective.

The CIS cars with the lambda circuit can really fool you, so learn about it and then start trouble shooting.

Lately there have been a lot of post about CIS problems, and I think some/most of it has to do with the cooler air this time of year. CIS (at start up) doesn't know that the air is cooler or denser than it was in the summer, so you may see idle that is not the norm.

Anyways, why do you suspect the WUR? I would not buy one, until you get a CIS pressure tester and verify your assumption.

[911nut]

Originally posted by dougcl
How the injectors deliver a varying amount of fuel with constant pressure escapes me. Perhaps someone can explain this.

The control plunger in the fuel distributor is acted upon by two forces as aptly stated by Doug; control pressure on top of the plunger and the sensor mechanism on the bottom.
The control plunger has six slits in it which allow fuel flow to the six chambers in the distributor via the plunger barrel. The position of the plunger dictates how much of the metering slit is exposed to the passages in the barell. The farther up the piston moves the more the slits are exposed to the passages and the more fuel is allowed to flow to the chambers, which, in turn flows to the cylinders.
Since the mixture is related to plunger position at a certain air flow, mixture enrichment can be varied by adjusting the mixture screw or, in the case when the car is cold, by varying the control pressure.
Hope that made sense