elgy

Today I had the intention to head up to Mont Tremblant to watch a Driver’s Education day at the course there. It was the first time on the freeway for more than 10 minutes for my 928. I ended up turning around and coming home after only about 40 kilometers because it just wasn’t fun. The engine felt flat at cruising speed and stumbled slightly. My experience has been that each time I don’t drive it it is very rough until it has gone a few kilometers and has been forced to accelerate hard a couple of times. It then runs reasonably well, but not perfectly. I had hoped that a highway run would help clean it out and get it running better. Didn’t work that way.
I have a new fuel pump coming this week that I will install just to make sure that that is not the problem and I will have a look at the spark plugs.
But sooner or later I am looking at cleaning and rebuilding the CIS system. Before starting I want to pull together as much as I can to be ready. I have read the following thread (and a few others) to get an idea of what is involved.
https://rennlist.com/forums/928-foru...b-wan-s-2.html
See post #33 in the above thread for a troubleshooting flowchart.

CIS primer (included from a link further down), this document has a huge amount of info. It applies directly to 911s with CIS but the theory and troubleshooting are useful for all CIS systems -
http://jimsbasementworkshop.com/CIS/
It includes a link to this theory of operation PDF -
http://jimsbasementworkshop.com/CIS/...IS%20Print.pdf

This video is a visual explanation of the system, Saturday comics for the technically minded. Warning the images are a bit jerky.

NB. - on the Warm Up Regulator. The above CIS primer calls the WUR the CPR (Control Pressure Regulator) which is a more accurate name, in my opinion. The CPR/WUR controls fuel pressure at all temperatures, not just during warm-up as the WUR name may suggest to the uninitiated (like me).

I have bookmarked the following sites for reference for the nitty-gritty:
6 page baseline procedure, this document is GOLD! -
https://928classics.com/resources/bo...onic-cis-fuel/

CIS resources -
Bosch manual entitled "Gasoline Fuel-Injection System K-Jetronic."
https://www.dmcnews.com/Techsection/...chtech-12d.pdf
--------------
as of February 2021 these links no longer work...
http://www.ferrari400parts.com/
including several documents available at:
http://www.ferrari400parts.com/kjetdownload.php
-------------
The above site talks about three kinds of Fuel Distributors: alloy adjustable, cast iron adjustable and non adjustable. I have not yet tried to figure what is on my ‘78 euro 928.
(EDIT - as mentioned further down in this thread I have a MB alloy adjustable FD. I have no idea how it got in my car)

A thread on FD rebuild with discussion on o-rings necessary and how to get the Richard Andrade rebuild instructions document.
https://rennlist.com/forums/928-foru...completed.html

FD rebuild video (Mercedes 8 cyl) -

Refreshing the air flow sensor
https://rennlist.com/forums/928-foru...ow-sensor.html

Post number #16 below has another good video on cleaning injectors for a Mercedes CIS.

Other FD rebuild instructions.
http://salvox.com/info.php?articles&articles_id=7

I found the following rebuild kits:
85 euros (dead link - see above)
http://www.ferrari400parts.com/catal...roducts_id/121
$128
https://cis-jetronic.com/index.php?r...product_id=147
$79.95
https://salvox.com
https://k-jet.biz/rebuild-kits/ $95 AUS?

Here is a discussion on CIS pressure testing equipment...
https://rennlist.com/forums/928-foru...equipment.html

Now some information on removing, cleaning and reinstalling injectors.
Injector removal
https://rennlist.com/forums/928-foru...oval-tips.html
… check out the video in post #2
More injector cleaning... back flushing
https://mercedessource.com/problems/...fuel-injectors

another on removal
https://rennlist.com/forums/928-foru...-injector.html

Injector assembly and installation
https://rennlist.com/forums/928-foru...tallation.html

Injector cleaning
https://rennlist.com/forums/928-foru...injectors.html

Advice on tuning...
https://rennlist.com/forums/928-foru...ext-steps.html

WUR repair and rebuild (warm up regulator)
http://www.ferrari400parts.com/Warmu...atorrepair.php (dead link - I have this document downloaded to my computer)
https://www.landsharkoz.com/tt/ttwur.htm

NB - I have added further links and info. in post #33

While in there I want to inspect and repair the vacuum lines and get my heater working and anything else that it would be logical to do (within reason… I am not ready to take the heads off).
I would appreciate suggestions on other reference materials, relevant threads etc. and what else I should consider doing at the same time.

Thanks in advance.

kiwiokie

AirtekHVAC

elgy

I have already done that, new hoses in the rear, new accumulator, new hoses in the engine compartment. My first aim is to clean the engine compartment components, but if I understand correctly they have to be taken apart for that so will rebuilt at the same time.
Thanks for the link.

elgy

Thanks Ron. I have started to reread the relevant parts of your "Official #30..." thread. Since the car is running and, as far as I know, has not been off the road for extremely long periods of time (2 years in my garage after I bought it and drove it for a few months), I hope it will not be as difficult as #30.

jpitman2

I found the Watson book on Bosch Injection very good, specially the troubleshooting areas. Price seems to have gone nuts since I bought mine, but keep an eye out for it second hand.
jp 83 Euro S AT 57k

linderpat

subscribed - looks like everything is being gathered here in hopefully a definitive thread.

karl ruiter

How about testing it to see where you are before you start tearing into it? Hook the system up the the fuel pump, get 8 mason jars and 8 lengths of fuel hose. Put the fuel hose over the injectors and run them into the mason jars. Energize the system, check your pressures, then look at what the system does as you vary control plate position. Total investment is about $30, and I always tend to end up here anyway anytime I have to mess with the FD.

STRIKEMASTER

KIWIOKIE is right. Be methodical about getting it to run right... I have an '83 Euro with K-Jet..Mine sat on a car dealer's lot for years and ran like crap when I drove it home. K-Jet is really a hydraulically controlled system.The system MUST BE SURGICALLY CLEAN inside or it will drive you nuts...For example: there's a very small port(.004") between the top and bottom of the F.D. that bleeds off 'control pressure' to the WUR...If it gets plugged you can't set the control pressure.....Start at the tank and work toward the engine, cleaning EVERYTHING...I replaced; Fuel pump, check valve, filter ( obviously). rebuilt the WUR, got a rebuilt F.D. from 928Intl. and replaced the injectors with M-B ****047 injectors...(I think the Porsche ones are NLA)....I cleaned all the lines out when I had it apart, blowing them back toward the fuel tank where possible.. You won't believe the gunk that came out.. The M-G injectors were about $40 ea. Now it runs pretty good, if I don't let it sit too long. LOL

kiwiokie

The Forgotten On

For anyone wondering, if your fuel distributor is a corroded mess you can replace it with an alloy one from a 450SL or similar Mercedes.

It bolts right in and just needs to be adjusted like the original with the same pressures to get it running right.

You can get the part at practically any parts yard.

Hey_Allen

That's good to hear.
I think I have one from a 500SE still sitting in my garage from when I was doing MB stuff, but it might flow too much for a 4.5L 928 motor.

The Forgotten On

You can adjust pressures on the metering head to fix that. Just get a A/F measuring device of some kind and go to town.

Jadz928

The MB flow similar or same. They use the same FPR, which can be adjusted to spec. The rest is done externally with correct injectors, WUR and AF screw set to spec.

gbgastowers