82 308GTSi fuel injection

Gentlemen:
I believe my 82 308 is running rich. I say this because it gets terrible mileage (approx 8 MPH) and the plugs are black - as they would be if the car was running rich. Does anyone have experience with the "how-to" books on Bosch fuel injection? I've read mixed reviews on other web sites. Finally, for those of us who have graduated from British SU carb vehicle there is a tool called a "Color Tune". Basically it is a clear spark plug which allows actual combustion to be viewed. The idea is to tune the car by color of the combustion. Might this work with the Bosch FI or should I let someone else set the injection?
Thanks in advance.
Steve Schroeder

Stephen,

Welcome !

Color Tunes are definately not just for SU's anymore! I have several and use them for a wide variety of helpful procedures, including looking at the ignition spark itself, besides inspecting the fuel mixture..

I'm sure one would be helpful leaning down idle mixture, however on the CIS systems Fuel Pressure is what controls the mixture the system runs at. To properly check your engines mixture conditions you will need to check exhaust emmisions at idle & part throttle before the Cats and record CO & HC readings and also check the Fuel System Operating Pressures and compare to the specs called for in the WSM.

If you want to do this you will need some special tools, an Exhaust Gas Analyzer & a Fuel System Pressure Testing Kit.

If you need more info just ask and we can guide you along the testing and setting procedures.

HTH's

Regards, JRV

This information is great, thank you. Perhaps I'm better off leaving this alone as the car does run well. I was under the impression that the mixture could be "adjust" at the fuel distributor (WSM page D-53). It states that turning a spanner right while enrichen the mixture while left will lean it. Do you happen to know the initial setting at the throttle body (throttle position adjustment and idle speed adjustment screw). Since I live in Oklahoma City it is a wee bit difficult to find mechanics that will work on something besides a pick-up.
Again, thanks for the information.

>>I was under the impression that the mixture could be "adjust" at the fuel distributor (WSM page D-53). It states that turning a spanner right while enrichen the mixture while left will lean it.<<

Stephen,

the adjustment you refer to only sets idle mixture. It raises or lowers slightly the FD plate/piston manualy, which in turn gives a little more or a little less fuel at idle only, afyer the engine comes off idle, the mixture is controled by system pressure and relative position of the FD plate, if pressure is to high, the plate is hindered in it's travel and the engine runs lean, if the pressure is to low, there is inadequate pressure on the plate, it travels too far and the engine runs rich. Of course there are other factors, but just wanted to give a simplistic overview of operation principal.

Leaving an engine running rich is very hard on the rings, cylnder walls, valves, guides and oil. So it's not really a good thing or something that should be ignored as the long term effects can be expensive.

Regards, JRV

Now I believe I might be getting a handle on this.
Basically there are two "circuits"; the idle circuit with rich/lean controlled by the initial position of the plate in the fuel distributor and a "running" circuit with rich/lean controlled by fuel pressure. That accounts for the accumulator and the fact that a clean fuel filter is very important. Perhap, it light of the special tools involved, I should take the vehicle to a mechanic with some experience in this area.
Thanks again.
Steve Schroeder

Steve
Good analogy, and it is even simpler than that. The whole thing runs on fuel pressure - the injectors are spraying all the time the pump is on, and the flow to the injectors (governed by the fuel pressure to them) is controlled by a valve controlled by the big plate.

More air flow - plate moves up and opens the valve allowing more flow to the injectors.
So the more the plate is up, the FI thinks there is more air and it allows more gas to flow to the always open injectors.

In addition to the cold start valve which just sprays gas into the plenum to richen the mixture at the start, all those other doofers around the fuel distibutor (the controlling valve) serve to control mixture strength by changing the pressure response of the valve (e.g. warm up regulator)or by modifying the air flow.

A change of the responsiveness of the main flow valve in the fuel distributor is what JRV is talking about: the control pressure.The control pressure is a seperate circuit where fuel pressure is used as a 'spring' or 'resistance' as it were against which the actuator plate must push against to move upward as he describes. So, if this 'control pressure' is not within design spec, the main metering valve will not control the flow to the injectors in the right proportion.

For what it is, the Bosch K-jetronic is a really brilliant piece of fuel control engineering for when it was designed and what it was designed to do.

JRV can better elaborate on the specifics of the system failures, but that's how I understand it: More air flow (pressure on the plate) gives more gas flow (pressure at the injectors).

Hope this helps
best
rt

The car occasionaly, and I mean occasionaly, acts as if it is "rich" before completely warmed up. This only happens right after the "warm-up" light has gone out (140 F or so I believe is correct) and lasts only 15 to 30 seconds. It is beginning to sounds, at least to a novice such as myself, that the idle "circuit" may be rich while the running "circuit" is fine. I suspect that the vehicle is on the idle circuit until perhaps 2,000 RPM or so at slow speeds - throttle plate not open very much. Does this sound right?
Steve Schroeder

Unlike carbs, there is no idle circuit. There is really only the main circuit which is modified by time, temp and vacuum through changes in the contrlo pressure. Later versions also have a feedback from an O2 sensor which modifies the control pressure we spoke of. It may be running rich across the band which may only show up at slower speeds. The WUR may lag the light going off in it's response.

There are also air bypass valves which can fail, but JRV could address that better than me.
JRV would be the 'Man' on this.

Hey you guys feel free to answer these questions....

much of this stuff certianly doesn't require my input as it's obvious many of you possess all the knowledge of systems and operational itricacies to carry on without me. In fact I really like it when guys are helping out (and impressing me at the same time {})and willing to help others.

The above is what community involvement and commradere is all about !!

The real underlying purpose here (to me at least) is to share with/create as many knowledgable guys as possible that can expertly diagnois and repair their own Ferraris and help others when needed. I like to see my role here more as a sounding board or just someone to fall back on when things really get tough rather than the guy who has to answer all the questions. IMO it is very helpful in any learning/renewing proccess for everyone to openly share.

Best Regards, JRV