bradartigue

Rummaging through posts I've seen quotes like:

"does your car have the cold start injector?"

and

"CIS wasn't really designed for an enrichment circuit but some cars have it."

Did all CIS cars, USA and Euro, have this? Like most early Bosch FI implementations it looks like a hack job on the 79, with two intermediate plastic air distributors inserted into the hoses and such. With the A/C hoses it offers more, uh, stuff to look at.

SMTCapeCod

I think all the CIS applications had a cold start valve.

Purportedly, some cars came with or were swapped to KE Jetronic, fitted with an sensor and electronics to modulate a frequency valve. I've never seen one operational on a 928, but that was the story.

The WUR, of course, is intended to modulate fuel pressure based on operating temp and the euros amplify that with a vacuum triggered enrichment function.

There is also a hot start valve that is only found on some model years, some of the time. It is pictured in the WSM, though I don't have the page handy. It is nestled down between the two back cylinders on the passenger side.

GlenL

There's the cold start injector that is on all cars and the cold start enrichment system. The later reduces pressure to the WUR and consequently the control pressure to the distributor. That causes an enrichment of flow from the 8 injectors.

SMTCapeCod

Oh, OK.
What part reduces pressure to the WUR then?

Below is what I was referencing.

GlenL

You've hit on the interesting part of this: it's not documented!

Check this post for pictures of the components.

"Hot start"

The active parts are a temp sensor and a valve. The poster thought it was about hot starting and others agree. In any case, the thermo switch controls a valve that controls pressure to the WUR.

I haven't found it actually documented anywhere. It doesn't show up in the standard CIS materials from BOSCH. Someone show I'm wrong and give some insight into this thing.

SMTCapeCod

The WSM calls it a "Hot Start Valve" and amplifies that with the description
"to Reduce Control Pressure for Warm Start" (in parens), that's sufficient for me.

Edit: As happens so often the OP of that thread decided to hit a couple different forums, and Landseer posted schematics, sourced from Morehouse CD, to PP:
http://forums.pelicanparts.com/porsc...t-valve-q.html

jpitman2

If its in the WSM, I would call that "documented" .
I have one of these on my 83 Euro - when the temp sensor (on the heater outlet elbow above cyl 4) closes (some funny range), AND the starter is cranking, a solenoid is fired (see wsm pic above) to reduce control pressure to assist starts when less than HOT, but more than COLD. The sensor on mine sort of failed - never less than 20 Ohms - which was enough to stop the solenoid firing. Replaced it, problem (waiting 10 mins more after stopping for 5-8 mins, and not starting) cured. The same system was used on CIS 944s also.
jp 83 Euro S AT 54k

GlenL

THe link shows a diagram from some sort of training materials. It's in German with English translations penciled in. Fun!

The crazy part is that reducing the control pressure will enrichen the mixture. Correct?

waynestrutt

http://www.mediafire.com/?j4cdfaaqiqggcw5

waynestrutt

GO HERE

http://www.mediafire.com/?j4cdfaaqiqggcw5

bradartigue

I don't have the warm start equipment; I have a cold start injector and aux. air regulator. All of this appears to be normal for a 79, even if poorly documented. The plastic multiport connector between the AAR intake side and the throttle body is a real afterthought piece, as is the "T" in the hose on the outlet side of the AAR for the A/C connector. Just not well thought through, which is why I ask, and the Porsche documentation is as vague as anything.