Jump to content

Robert Bosch's K jetronic CIS fuel injection

Recommended Posts

I have a Ford sierra 2.8 xr4x4 from 1986, its been in the fam since new and is exactly as it left the factory in Genk, Belgium all those years ago. It starts and runs pretty good although no longer as smooth as it was and I'm thinking the injection system has been working away for thirty four years and has never been given any attention, not even the injectors themselves which, according to the maintenance manual, require replacing every 100kkm and there's at least 300kkm on the clock.

The injection system is the Bosch constant injection system, mechanical of course, not a computer in sight. This system was used through the eighties by VW, Mercedes, Porsche, Audi, Volvo and maybe Jaguar so anyone out there with any of those vehicles from that far off era will know what I'm talking about. So if there is anyone who has experience of dealing with this system especially the fuel distributor, I'd like to hear what you have to say because sometime soon I'm going to have to take this old thing off the road and yes, it's our daily drive, and yes, we know we're crazy, and I'm going to have to at the very least replace the injectors, and rebuild the fuel distributor and, you know, give the old thing some love.






Link to post
Share on other sites
3 hours ago, ajg193 said:

@kws is the resident expert

It does seem that way.

The first step is to run some injector cleaner through the system, and change the fuel filter. You might find if you haven't done this in the while it clears up a bit anyway. If it doesn't, you will need to start delving deeper (as long as you know its fuel related, and aren't heading into a world of pain for nothing if its ignition or intake/vacuum leak related instead). You should also do your valve clearances if you haven't recently.

After going through the pain of making the non-functioning KJet in my TVR (which will be exactly the same as in your Sierra as its the same engine) work again, i made a series of guides to help anyone else through the testing, diagnosing, troubleshooting and configuring of the system.

Part 1, The Basics

Part 2, Testing

Part 3, Tuning and Fixing

Hopefully that helps you get it sorted. Happy to help if you have further questions.

  • Like 6
Link to post
Share on other sites

K jet is a funny old thing, don’t fuck with it till you are 100% sure, 


I run Moryes upper cylinder lube with every tank of fuel, and almost 3 times the recommended amount, the tops of the intake valves and intake manifold are silver with no carbon, used to be black when I 1st got the car.

  • Like 3
Link to post
Share on other sites


Thanks for the reply, your guide is just the thing, incredibly detailed and covers everything, quite a piece of work.

Thanks for the numbers. Those injectors are available from Oz ex Deutschland, actually cheaper from Oz at $54 plus shipping and stuff than if I buy them in Deutschland itself. The fuel distributor is weeping a little from the bottom of the plunger so I'm eventually going to have to do the seals in the thing but I don't feel it's urgent at this stage. The car runs well, plenty of ancient grunt, the only real concern I have is the motor has a significant vibration at 2 - 3000rpm and I finally figure it must be a power imbalance between cylinders or bangs of different intensity, so new injectors can't do any harm. Meanwhile nothing's going to get done until I get less busy and find space and time.


Thanks for the tip, radical and I'll try it.



Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...