CIS injectors injecting continuously
 

OK, I got the ingine in and mostly installed without bugging the board much, but now I have questions:
I bought a 1974 911 2.7 with CIS with a wrecked engine, almost all parts included but the ignition and CIS in pieces. These have been re-assembled in a fashion that appears to match the diagrams (here and at the enormously helpful CIS primer http://members.rennlist.com/jimwms/CIS/CIShome.html).
But, when I turned on power to the pump, expecting to check the spray pattern while fiddling with the air plate, all injectors started spraying continuously. This richness does not seem like a cold start valve problem, so what would be the next adjustment? Moving the plate does not affect the pressure.

Thanks, and I have already looked for obviously titled threads in the archives.

Perhaps the fuel distributor metering valve is stuck?
-Chris

CIS....Continuous. Injection. System.

Yes... continuous injection is correct vs. sequential fuel injection.

targa911: Sigh. Yes CIS = Continuous Injection. He knows that. CIS squirts when the air meter is moved up by air - not when the just the fuel pump is running i.e. the fuel distributor only supplies fuel to the injectors when the motor is running.
kellzey: CIS is not the "flip side" of sequential injection. Sequential is just a flavor of Electronic Fuel Injection
-Chris

Dr. No,

First of all...'sit down'...(sorry no caged spider available ;) )

I have the same '74 motor...the idea is that these spray continously from the moment power is applied to the fuel pump...air sensor plate meters the volume delivered depending upon condition...this is normal operation.

Btw, sorry Crab Key was destroyed...I was just doing my job...;)
Ryan (007)
:cool:

i bet chris is right. the injectors dont spray when the engine is not running. you need the pillow of air to hold up the sensor plate. take the fuel dist off partially and peek under it, is it stuck. a good indication, is also; when you lift the plate manually, do you feel any resistance? no resistance like a perfectly balanced balance (that was an awkward sentence, sorry) usually indicates a stuck control plunger. even zilcho fuel pressure, there would be a tiny bit of resistance. but you already proved there is fuel press.

cliff

Ack...my bad...Cris is right...they only should flow while the engine is running and the air sensor plate actively metering a fuel volume. Started to sound like maybe a stuck comtrol plunger...need to think a moment here...
Ryan

I did some work on a '74 CIS that had been sitting for a 10 years. The fuel distributor was gunked up enough that air wouldn't lift the plate but I could lift it by hand. To start the car I needed to lift the play by hand but after running it for a couple of days it worked fine.
Thinking out loud...
If your fuel distributor is stuck open I would think that the air meter plate would move with no resistance at all and then hit the "pill" that meters the fuel. If the "pill" is really stuck, the plate would stop right there. If the pill is just gunked up, you would be able to move the plate up further with some "gummy" resistance.
-Chris

I'd also start at the fuel distributor.

I'm with Chris on the stuck control plunger...it's the only think that would allow fuel to flow to the injectors...should be closed without engine running, but yours is apparently open. It's possible that the pivot lever between the air sensor plate and the plunger is having no bearing because the plunger is already stuck 'open' or 'up'....so movement of the plate has no impact, matching your symptoms.
Ryan

try just cranking the adjuster counterclockwise until they just stop spraying. if the piston was stuck you would feel no pressure on the sensor plate arm when you lift it, or at least some freeplay. the arm lifts the piston.

Chris: sigh, that was tongue in cheek. I know nothing about CIS. I leave that to you experts. I've got my hands full with my MFI.

Sorry. I must be grouchy today.
-Chris

I understand...it's cool.

Thank you all for your replies.
Yes the plate bounces up and down with no resistance or effect on the spray.
Is there a way to free the piston without taking the whole fuel distributor apart? I have "spare" CIS unit from a Rabbit I will dissect later for more data (it also bounces freely, but there is no fuel pressure to deal with).


And, yeah, I didn't thing 'continuous" meant filling up a couple of cyliders before applying spark.

You can blow compressed air into the top, center port to loosen the stuck plunger. You'll probably want to remove the fuel distributor from the sensor plate housing first. Be sure to catch the plunger so it doesn't go flying. I wouldn't recommend disassembling the fuel distributor unless completely necessary. I've done it, but it was a huge pain to get it sealed up properly afterwards.

-Rob
1980sc

I think I'll try the compressed air route. The fuel distributor can be removed from the air box without dissasembly. Here are pictures from the 4-hole rabbit version. http://forums.pelicanparts.com/uploa...1079492183.jpg http://forums.pelicanparts.com/uploa...1079492198.jpg

And by the way, that was not really Crab Key--it was a decoy. Your day will come, Bond...

But...I saw you disappear into the radioactive vat...?! Curses...
Ryan