New CIS problems...for me

911fan77 · 05-22-2005, 08:05 AM

I've got a 77 2.7 with new SSIs and muffler.

I had really bad exhaust leaks on the old OEM HEs and I replaced two defective fuel injection lines. It ran pretty good when the old HEs were on and the injection lines were replaced. Ever since I replaced the HEs with SSIs, my startup when cold is horrific. It takes along time and then sounds like only 4 cylinders are turning. After a minute, it evens out and sounds like 6 cylinders are going. The smell of gas is in the air like it is flooded for a small time. I'm also having the same problem of it occasionally backfiring thru the air nozzle when cold but runs good after a few minutes. After it runs warm for a bit it has backfired thru the exhaust when warm once while it was idling. It also will backfire on deceleration thru the exhaust occassionally when driving. I suspect that after the exhaust leaks were fixed via the new SSIs, I might be running a little rich. Before I start replacing the WUR and AAR (as suggested on other threads), I'd like to get the opinions of others on where to start. Should I try to adjust the fuel mixture first?

I also have a few questions about the vaccumm connections like where do they connect? Is there a general vaccum diagram?

From the WUR:

and from the value on the back of the throttle body:

Any help is appreciated.
Thanks,
Dean

Jim Williams · 05-22-2005, 11:22 AM

For starters, check out this web site, it'll have the answers to your questions about the vacuum line connections.

http://members.rennlist.com/jimwms/CIS/CIShome.html

cmonref · 05-22-2005, 11:31 AM

Right after you check Jim's website for information about CIS, resolve to NOT start adjusting things!! If the engine was running OK before you replaced the SSIs, then something you did during that process has caused the running problems.

In answer to your questions, correlate Jim's information with the parts pix that are on the Pelican website. For instance, for 78-83 SCs, pix 1-7-2 shows both of the items in your posted pix. Check for similar pix specific foryour '77.

The poor running upon cold startup could be related to the missing vacuum hose in your top picture. Hoses missing from the decel valve in the bottom picture could be related to warm running problems. Other missing hoses could be producing serious vacuum leaks that would produce the symptoms you describe.

Don't adjust ANYTHING until you get all the pieces in place and hooked up. If you did not adjust the fuel mixture as a part of installing the SSIs, then do NOT adjust it now.

Good luck tracing all of those hoses.

911fan77 · 05-22-2005, 11:55 AM

Thanks Jim and Brian. Those hoses were not there before the work was done but I wanted to figure out why. I've also been wanting to check/replace existing vac lines anyways. I'll track those down and move on from there.

Thanks,
Dean

Paulporsche · 05-22-2005, 06:40 PM

Check the exploded views section of this site for diagrams on vacuum line routing.

911fan77 · 05-29-2005, 08:32 AM

Ok. Hate to revive a dying horse here but I just got around to checking the vacuum hoses. Looking at Pauls exploded views (which is exactly like my diagram from the 77 parts catalog)

http://www.pelicanparts.com/911/911_Parts/1978-83/1-7-2.JPG

I see a thermo valve labelled 17A that is connected from the WUR and also connected via a t-connector to the front of the throttle body and to the top of the decel valve.

First off, where is the thermo valve located? I can't seem to find one in the engine compartment. It looks as though I am without a thermo valve and the leftmost connector on the WUR is open.

As my connections look right now is I have no hose off of the WUR (lower left which in the diagram is connected to the left-most connector on the thermo valve). My decel value is connected to the back of the throttle body mid way down. On the front of the throttle body I have one hose leading from the top connector to the WUR (as shown in the diagram) and one from a valve on the distributor which connects on the bottom connector on the throttle body (which the diagram shows hooked from the thermo valve).

Is the thermo value required? If not, what is the valve on the distributor? Also, what do I do with the open connector on the WUR?

Help help is appreciated...
Thanks,
Dean

bigchillcar · bigchillcar's Garage

your distributor should have either vacuum advance or retard, depending on model..if you have a vacuum connection attached to it. as many pelicans as should be in north carolina, i'd try to hook up with one who's very familar with the cis layout and properly baseline your car..once you have confidence that all vacuum lines are in place, then i'd find a shop with a gas analyzer and resolve the mixture question once and for all. oh yeah, then go enjoy the car with confidence. good luck.
ryan

Jim Williams · 05-29-2005, 03:32 PM

Dean,

Look on my website

http://members.rennlist.com/jimwms/CIS/CIShome.html

Find "CIS Components" and scroll down to Thermal Valve. Click on the words "Thermal Valve" to see a photo. It should be on the left side of the engine just under the heater blower if your car has one.

Yes, it is required if you want the engine warm up mixture that this valve helps provide.

If you'll look on this same page, check out the WUR photos. Look at the bottom photo. This shows where the vacuum lines should connect to the WUR for the different model years. The connection in your photo at the bottom of the WUR is an "atmospheric" connection. It should go to a place on the throttle body that develops no vacuum, a port above the throttle plate. If you leave it open, the only effect could be that it will get some contaminant in the hole, like water or ?. The Pelican drawing is from the Porsche factory parts manual, and actually shows the connections for a '78 - '79 WUR. The '76 - '77 WUR vacuum connections are actually opposite to this.

The problem with using the Porsche factory parts manual as a connections diagram for a particular year of car is that this diagram is a generic diagram covering several years of CIS, and is meant only to serve as an illustration for the part numbers. For example, the thermovalve and the connection of the WUR fuel return line to the Fuel Distributor didn't occur on the same year model.

I think the hose you are describing as connected to the top of the throttle body is not a "vacuum" hose at all but rather the atmospheric connection for the WUR, so my guess is that your WUR may not be receiving any actual vacuum input at all. (The "front" of the throttle body is usually described as the side nearest the front of the car.)

Hope this helps.

911fan77 · 05-30-2005, 03:59 PM

Jim,

Thanks for the explanation. The top vacuum port goes to the top port and the vacuum advance goes to the bottom port on the back of the TB (towards the rear of the car). Currently the atmospheric conn. on the WUR is open and the top of the decel valve is connected to a port on the front side of the TB. Now if I add the thermal valve and lines from the WUR atmos port to the TV and then from the TV to a t-connector, I could add the top of the decel valve and all others to the same port on the front side of the TB. Does that make sense? If the port the decel valve is currently hooked to is an atmospheric port. Which I have no clue. Does anyone else?

Here's a pic of another TB and the current connection of the decel valve: