Dave928S

That's the best one around .. and was the one I was going to send broken into three files ...

That's the connection for the fuel consumption meter gauge which only some cars have ... Euros??

Jim ... You say the car gave this idle problem when the car was hot and you also had the A/C on ... when it was hot did you only get the issue when the A/C was on? Have you checked the A/C idle solenoid?

jwillman

I have never noticed an appreciable change in idle RPM when engaging the A/C. How much should I see? Is there a bench test for the solenoid?

karl ruiter

If you want to try removing the decal valve, you can use endcaps for 1/2 copper pipe to block the two large hoses.

jpitman2

I see a definite idle lift with AC on. remove the hose from one side of the solenoid, turn on ign and ac, and you should be able to blow through. Turn off ac, idn, should not be able to blow through.
Is there a down side to removing the decel valve ?
jp 83 Euro S AT 54k

Podguy

The very early cars do not have the A/C valves. I have never observed any change in idle due to the A/C on.

I do not see the Decel Valve as an issue with the description of the problem. If the car jerks as it decellerates when coming to a stop then the decell valve is not working correctly - probably the diaphram is shot. The purpose is to burn some unburnt gas to help with smog. I have always found the car to drive better when the valve is blocked. I have never seen a smog shop test it.

jwillman

I have no issues with deceleration and the car is not subject to emissions testing so no worries there.

karl ruiter

The function of the decel valve is that under super high vacuum conditions it lets some air past the throttle valve. The problem I have seen with them is that sometimes they leak intermittently and let air past when they should not. This results it a higher idle. Suppose you set your idle speed when it is leaking and then at a different temperature or vacuum condition it seals up tight. Suddenly your idle is gone. I have had this issue on two separate motors.
The down side of removing it is that when you do drop the RPMS fast sometimes the idle speed will undershoot....go very low and then come back up.

jpitman2

Dave,
I dont have any sort of economy meter....so I dont know what the funny FD connector is for. Reconnecting it seemed to improve the hot start issue for me back in the early days.
jp 83 Euro S AT 54k

Dave928S

That's interesting. It definitely connects to the fuel economy meter on mine, so maybe on yours it might be necessary for it to connect to a dummy load to replicate that ??? .. have you ever traced it out to see where it goes?

Jim .. I checked PET and Dan is correct about the A/C solenoid, which ups the idle when the A/C's on ... I don't see it on the early cars. Sorry to send you off on a tangent.

jpitman2

I have never even thought to trace it out. I have the hot start solenoid thing on the heater outlet that I mentioned earlier, and I thought it was relevant to that. Have never seen this on PET I dont think, buts in the WSM, covering diagnosing if its leaking or not.
jp 83 Euro S AT 54k

Luis_M

@jp: Are you talking about the hot start solenoid valve 928 605 103 00? (NB:corrected p/n; thank JP) It is #1 on illustration 107-30 in the 82 and 86 ROW PET PDFs.

The fuel consumption gauge started appearing in 1982 but IIRC the connector for CIS cars is supposed to be on the side of the air guide/meter housing, not on the actual fuel distributor. What is the part number stamped on the fuel distributor? Is it original? A plug on the distributor itself makes me think it was lifted from a CIS-E car (maybe a Mercedes)

Added: Here a pic of the fuel-economy-gauge plug (circled) lifted from another thread (not my car, see plug on the air guide housing): https://rennlist.com/forums/8737661-post38.html

____
Luis M
1981 928S Euro 5sp

SMTCapeCod

Interestign, I thought that was frequency valve for KE Jet (other applications). What creates signal for the fuel eco gauge? Potentiometer on the armature for the throttle plate?

jpitman2

I make the solenoid 928 605 103 00, item 1 on that page. I dont think I have the damper, item 13. Next time I have the air cleaner out I will take a pic of the connection on the FD and post it. Looking at the pic, maybe it is on the air housing, and not the FD itself...getting curious now.
jp 83 Euro S AT 54k

Dave928S

Here's the connection point on mine ... original motor in my Oz delivered car with economy meter ... must be some sort of rheostat connection to the plunger?

Luis_M

thanks, typing too fast I put the part number on the next line. I corrected my post with the right part number.
I assume you mean item 15 for the control pressure damper. My car happens to have both.

Does anyone have the technical bulletin mentioned on this PET page? "for subsequent installat. see technical information GRP.2 NR.9". I'm interested to see when Porsche would have recommended installing the hot-start solenoid valve, damper, or both, since the diagram shows several variants of the hard lines for installing both together or one without the other.

Luis M
1981 928S Euro 5sp