cis injector idle problem
Thread Starter
8th Gear
Joined: Dec 2014
Posts: 8
Likes: 0
cis injector idle problem
Hi there, I'm new to rennlist. I am piecing together a Porsche 928, 1980 4.5l Euro model.
The issue that I have is that when testing the fuel distributor, when "idling" (no airflow, lever arm isn't pushed down at all), the fuel distributor only sprays out of 1 injector with a high pressure (so high it doesn't mist, and you can see the spray pattern clearly), but as soon as you push down on the lever arm then the rest of the injectors spray.
Is this the normal operation of the fuel distributor, and if not, any ideas on where to look to try rectify this issue?
Thanks
The issue that I have is that when testing the fuel distributor, when "idling" (no airflow, lever arm isn't pushed down at all), the fuel distributor only sprays out of 1 injector with a high pressure (so high it doesn't mist, and you can see the spray pattern clearly), but as soon as you push down on the lever arm then the rest of the injectors spray.
Is this the normal operation of the fuel distributor, and if not, any ideas on where to look to try rectify this issue?
Thanks
Rennlist Member
Joined: Dec 2007
Posts: 1,622
Likes: 13
From: Ringgold, GA
This is a great resource for CIS related issues
http://www.928classics.com/4/post/20...ide-78-79.html
http://www.928classics.com/4/post/20...ide-78-79.html
Thread Starter
8th Gear
Joined: Dec 2014
Posts: 8
Likes: 0
medipedicman: thanks for that, i'll definitely check that out.
LT Texan: they do all spray but only once i start to push down on the arm. As soon as the arm goes up to its resting position (all the way up), only one injector is open, the one right on top of the fuel line to the starter valve.
Jadz928: I have swopped out the injectors, and the same issue occurs. Sometimes though when I swop it out, the high pressure just moves to another injector, normally the one just over the inlet line, but sometimes its random.
LT Texan: they do all spray but only once i start to push down on the arm. As soon as the arm goes up to its resting position (all the way up), only one injector is open, the one right on top of the fuel line to the starter valve.
Jadz928: I have swopped out the injectors, and the same issue occurs. Sometimes though when I swop it out, the high pressure just moves to another injector, normally the one just over the inlet line, but sometimes its random.
Thread Starter
8th Gear
Joined: Dec 2014
Posts: 8
Likes: 0
Just an update: I tested the injectors, they're all fine and unblocked. I believe the problem lies in the fuel distributor, because I disconnected all the fuel lines that connect the injectors to the fuel distributor, and I sprayed carb cleaner into those holes while the arm up. There was no flow for 5 of the 8 holes, but for 3 of the holes there was a flow that leaked into each other and into the start valve outlet.
Any ideas what could cause that? My guess is that the small o-rings on the inside for the 3 that are leaking into each other aren't sealing.
Any ideas what could cause that? My guess is that the small o-rings on the inside for the 3 that are leaking into each other aren't sealing.
Rennlist Member
Joined: May 2001
Posts: 5,282
Likes: 16
From: Austin, TX
Well you've confused me.
There are 8 injectors to the intake runners and one "cold start" injector to the plenum on your model. (If I remember correctly.)
How can the 8 spray when you push down the arm with 3 clogged fuel lines to them?
And are you saying that the cold start injector is always open?
There are 8 injectors to the intake runners and one "cold start" injector to the plenum on your model. (If I remember correctly.)
How can the 8 spray when you push down the arm with 3 clogged fuel lines to them?
And are you saying that the cold start injector is always open?
Trending Topics
Thread Starter
8th Gear
Joined: Dec 2014
Posts: 8
Likes: 0
LT Texan: okay let me clear up the confusion. Yes that is correct, 8 runners and 1 "cold start" injector.
There is no blockage in any fuel lines. Its when the arm is in the "idle"/arm completely up that 1 of the runners is still spraying whilst the rest do not.
the cold start injector is always closed.
There is no blockage in any fuel lines. Its when the arm is in the "idle"/arm completely up that 1 of the runners is still spraying whilst the rest do not.
the cold start injector is always closed.
Rennlist Stories
The Best Porsche Posts for Porsche Enthusiasts
Talos Takes Your 991 Porsche 911 GT3 to the Next Level for a Cool $1.13 Million
Verdad Gallardo
9 Vehicles Porsche Helped Engineer that Aren't Porsches
Verdad Gallardo
9 Features and Characteristics That Only Porsche People Understand
Verdad Gallardo
I've Written 500 Rennlist Articles: Here's How Porsche Has Changed Along the Way
Joe Kucinski
10 Most Unnecessary Porsches Ever Built (And Why We Love Them)
Verdad Gallardo
Porsche 911 GT3 S/C vs 718 Spyder RS: 10 Categories, One Winner
Joe Kucinski
This Builder Is Turning Heads With Its Slantnose 911 Creation
Verdad Gallardo
Porsche 911 GT3 Artisan Edition Pays Homage to Japanese Culture
Verdad Gallardo
Porsche Reveals Coupe Variant of the Electric Cayenne With a Fresh Look
Verdad Gallardo
Rennlist Member
Joined: May 2001
Posts: 5,282
Likes: 16
From: Austin, TX
Since the problem did not follow the injector, You'll need to replace the fuel distributor with a new or rebuilt unit. Or rebuild it yourself. There is a link to a rebuild procedure on the link in the second post.
Rennlist Member
Joined: May 2003
Posts: 8,706
Likes: 153
From: Frankenmuth, Michigan
What's happening is your fuel distributor diaphragm (thin metal plate btw the two halves) is no longer sealing on at least one port.
Also worth noting, the link mentioned above offers a rebuild service too... for those not inclined to diy their FD.
Here's a shortcut to it - http://928classics.com/cis-service-and-parts.html
Here's a shortcut to it - http://928classics.com/cis-service-and-parts.html