'77s CIS sensor plate stuck? Help please
 

I'm new here, and need some help getting my '77 911s back on the road. I bought the car and it hasn't run for 10+ years.

I've performed the basic fluid changes, ignition tune up, fuel tank, pump and filter change. What I've got now is a CIS issue that I need to get to the bottom of.

With the pump running, I've got the slightest drizzle of fuel at the injector, however the sensor plate appears or fuel distributor piston appears to be stuck. Inside the airbox, I can pull down on the sensor plate arm slightly, however have no movement upwards. If I press up the fuel pump will turn on, but I have no actual movement upwards.

I'm still new to CIS. What are the next steps to diagnosing this? Has anyone else encountered this problem?

Welcome! If you can, please post some pics of your car and engine - it will help the rest of us provide decent advice.

You most likely have gummed-up gas in the fuel distributor. Before tearing into the CIS, I highly recommend looking at this info:

911 CIS Primer - Index

I also recommend searching the forum here and reading through a few of the CIS rebuild threads. This will help you understand what you're in for.

With engine not turning and the fuel pump running, you should not have any fuel coming out the injectors. The sensor plate needs to lift to get the injectors to spray fuel.

In my opinion, there are no easy fixes for this and you'll most likely end up pulling the CIS off and doing a full clean-out...

[BIG EDIT - I originally had some instructions in here about recircing fuel with cleaner and trying to wiggle the piston free, but a post below reminds me about how much trouble you're in if the piston sticks completely in the fuel distributor head. I'm pulling this info to prevent spreading a bad idea.]

Good luck!

You'll need to free up the stuck control plunger in the fuel distributor; this is very common when these engines sit too long without proper storage measures.

You can pull the fuel distributor off in the car, just pull the lines and there are 3 flat blade screws screw on the top, remove those and you can wiggle the distributor out. If you can free up the piston great, free being that it drops with its own weight. More info here so you can see what you are dealing with:

http://forums.pelicanparts.com/porsche-911-technical-forum/272657-cis-fuel-distributer-cleanout-w-pics.html

Thanks for the links, and the great information. I'm going to spend the rest of the day reading up on the CIS primer and some of the links on here. Hopefully I can un-stick the piston, otherwise you might see a post from me seeking tips on removing and rebuilding the whole CIS system.

As requested, here are a couple pictures of the car and engine (1977 911s - Imgur). It's a 1977 911s Sportomatic. I was looking for a project SC or Carrera to compliment my Boxster S when this car fell into my lap at an amazing price. The body and interior is in great shape, and it spend it's 10 year hiatus sitting in a climate controlled garage.

If this turns out to be a stuck piston in your fuel distributor, you can try this: My piston was stuck and would not budge. I soaked in various penetrating oils without any luck. Somebody recommended a 50/50 mixture of ATF & Acetone. I tried that and the piston popped out so fast it almost hit the ground. I was amazed since I had been trying to get the thing loose for at least a couple of weeks.

So quick question - did you submerge the whole distributor into this mixture, or did you pour it inside?

After 10 years I would buy new injectors and send the fuel distributor out for rebuild or source another one. If those two components aren't working right you will always have problems. The wur is also a key to proper fuel delivery.

CIS components.......
 

Eric,

What's the Bosch part numbers on your FD & WUR? Are they -006 and -033 respectively? I don't know how urgent you want to get them fixed but if you would still need some assistance by March (Spring time) PM me. I'll be on the road travelling in six (6) days from today and won't be back home tinkering CIS components till this spring. Keep us posted.

Tony

don't try to push the FD piston into the body by lifting the sensor plate. it's easier to get out if you can grab the little tit on the end. do not drop it or touch the outside of the piston with anything that will leave even a microscopic mark or it will bind and/or leak gas.

I squirted a little bit into the top port (where the WUR fuel line connects) and also I turned the fuel distributor over and squirted a little into the center hold where the plunger moves. It only took a couple of minutes and then the plunger just popped out.

Tidybuoy, you are the king of CIS! Your trick worked perfectly. I bought Acetone and ATF, and mixed a 50/50 mixture in a plastic squirt bottle and shot it in every available port into the FD. About an hour later I was doing some other stuff on the car and I heard a PING sound, which was the sound of the piston dropping against the metal work bench! When I pushed it back up it moved freely!

I put the FD and sensor plate together, bled the acetone out of the injector lines, hooked everything up and the car started on the first try!

I let it run up to temp, tomorrow it moves under it's own power!