Project Rabbit GTI: Repairing and Rejuvenating Our Bosch CIS Injection

Our VW Rabbit GTI, turbocharged by Callaway back in the day, now looked good. The blemishes had been fixed, and we even redid the bumpers.

Now it was time to bring the car back to life.

We figured that we would start by eliminating any ignition problems before we even dove into the fuel injection system, so we installed a tune-up kit: new plugs, wires and distributor cap. We turned the engine over and had good spark.

Next we got both a wiring diagram and checked the entire system. We found some frayed wiring behind the engine and corrected that.

Now to look at the injection. The Rabbit GTI uses Bosch K-Jetronic CIS fuel injection. This essentially a mechanical continuous injection system (as opposed to a modern pulse-type fuel system) with some electronic add-ons, like the cold-start injector and the warm-up regulator.

This video provides a good explanation of the system.

While this system was also used by Porsche, BMW, Audi, Mercedes-Benz and others up until the mid ’80s, these days parts and expertise can be hard to find. Plus, CIS doesn’t like to sit.

We replaced the battery and fuel filter and, not surprisingly, the engine wouldn’t fire. We couldn’t hear the fuel pump.

We determined that we had power and a good ground to the electric fuel pump (located near the fuel tank in a Rabbit), but since the fuel pump still would not work, we decided to replace it and the relay that accompanied it. Still no running engine.

We then tested the fifth injector–aka the cold-start injector. It was now getting fuel and seemed to operate fine.

We were also able to trigger the sixth injector, added by Callaway and controlled by a crude, kind of cute auxiliary ECU hidden under the glove box.

We also tested the injectors (which were somehow fine) and replaced the injector shrouds and O-rings as they are inexpensive and fuel leaks are rather dangerous.

This got us fuel to the engine and little else. When we manually lifted the metering plate, however, we could start to make the car sputter. Call it a sign of life.

The fuel metering block (or unit, or distributor, depending on who you talk to) seemed like the logical culprit.

While you can rebuild these yourself, we were warned that our chances of getting it right due to all of the little plates and seals was slim to none. Fortunately, we were pointed towards the Fuel Injection Corporation, who could rebuild our unit (if we supplied a core) for about $300.

The rebuilt and returned our unit. While we could now get the engine running, it would only fire for a few seconds. Then silence.

Next we tested the warm-up valve that helps this rather crude system deal with a cold engine. We were able to clean and rebuild the old warm-up valve, which is good since these valves have become expensive.

So, we tried firing the engine again. It would now idle–making progress–but would not accelerate.

Time to look at the distributor. Sure enough, we were not getting any vacuum advance.

As Techtonics didn’t have a replacement distributor in stock, we found a Bosch unit on eBay for less than $150. It was close, only needing some connections changed–no big deal.

Now, finally after spending about $500, we got the car running.

At this point, we could really hear the exhaust leak that the previous owner had warned us about.

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View comments on the CMS forums
Stefan (Forum Supporter)
Stefan (Forum Supporter) MegaDork
9/21/20 2:46 p.m.

Need a spare engine?

Maybe you could build one up with some more modern aftermarket bits?

I think everyone who has a CIS equipped car should read this post.  CIS is a huge pain to deal with if you're inexperienced with them and many, it seems, are not experienced with them.


Tim Suddard
Tim Suddard Publisher
9/22/20 5:53 a.m.

In reply to Stefan (Forum Supporter) :

Once you have it back up and running, it seems pretty decent. Our goal was to restore a cool old car of the eighties and not slide down that slippery slope to make a new car out of this one.


Stefan (Forum Supporter)
Stefan (Forum Supporter) MegaDork
9/25/20 5:34 p.m.

In reply to Tim Suddard :

Understood.  It seems that Porsche 924 folks struggle more than other cars equipped with CIS and I don't quite understand why.

As for building one up, I was thinking it might make an interesting set of articles discussing whether small improvements like converting to EFI or a more modern turbo make enough of a difference to take the plunge.  Something that is often discussed, but often falls into the "butt-dyno" territory.

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