K-Jetronic Fuel Injection System Overview

[Phalcon51]

Here's a good educational resource I found this morning on the K Jetronic system.

http://www.auto-solve.com/mech_inj.htm


This British company has a technical CD ebook for sale with this and a lot of other information on it. Here's a complete list:

http://www.auto-solve.com/description.htm

They also sell some 2-pin break-out leads for multimeters and oscilloscopes. I'm not sure of the usefulness for the typical DIY'er - maybe one of the more technical types here can comment on that. Here's the link to that:

http://www.auto-solve.com/products.htm

and a list of the uses for the multimeter leads:

"Typical applications are: multi-point injectors, some Lucas / Rover spi injectors, crankshaft position sensors (inductive), camshaft position sensors (inductive), coolant temperature sensors, knock sensors, some Vauxhall ignition coils, some Austin Rover ignition amplifiers, pulse air solenoid valves, Bosch K-Jetronic thermo-timer switches, cold start injectors and warm up regulators, to name but a few."

They also have a discussion board available, though it doesn't look like it's used a lot. Could be useful, though.

Hopefully, this will help those of us who think that fuel injection is just a bunch of black magic

Gary

[afmcorp]

gary

thanks for this good info link.

[Mike Murrell]

The last URL shows a 2-pin break out lead that looks very much like the baumtools.com connector used to measure EHA current.

A few months ago this connector was $20. It's now $40.

[Phalcon51]

So should we all run out now and buy one before it goes up to $80?

Seriously, though, would this be something that would be useful for the average DIY'er? Can it give us some useful information for some of the more common problems these cars have?

Gary

[Mike Murrell]

If you want to read EHA current, you'll need MB part # 102 589 046300 or reasonable facimile. I'm reading it straight off the tag.
Again, I bought it from baumtools.com. I'm sure there are other places that sell it.

Some MB dealer sells tools/test equipment and some do not. The one in my area will not sell any special tools.

The part is mentioned by number in these threads:

http://www.peachparts.com/shopforum/search.php?action=showresults&searchid=563285&sortby=lastpost&sortorder=descending

The part number varies in some cases.

Look at these threads and also search on EHA.

[locry]

great info,

i have a question though, where does the 02 sensor fit into all this? what/when/how does it regulate whatever?

[sbourg]

Computer control of engine operation requires a completed 'loop' to properly make needed adjustments. For mixture control, the O2 (lambda) sensor is the input to the loop that tells the computer whether the mixture is too rich or too lean. The EHA is the electro-hydraulic device by which the computer makes the necessary adjustments to get the O2 sensor reading back into the correct zone.

Steve

[locry]

thanks for the response.

so in actuality it just regulates how much fuel is injected? what happens when the o2 sensor fails or is removed? i found out that i've been running my 190e 2.3 8valver w/o an o2 sensor, it seems to run ok, one click starts, idles smoothly... though there's a strong exhaust smell...

[sbourg]

The basic Jetronix K mixture control is via a pushrod connecting the flap of the airflow meter to the control slits inside the fuel distributor. Fuel delivery to the injectors varies by the position of the flap - i.e. airflow demand. All the ECU does in the KE is fine-tune that by varying secondary fuel pressure via the EHA. If the car won't run with the ECU out of the loop, something is mechanically misadjusted.

Steve

[locry]

cool! so it just fine-tunes the mixture... i read somewhere that without the 02 sensor the injectors would be injecting constantly, or at full power, so without the 02 i'd be running super rich than normal.

so right now i'm running w/o an 02 sensor, i'm running rich aren't I? but not super rich...

[sbourg]

You could be rich, lean, or at stochiometric ideal. Basic mixture setpoint is a mechanical adjustment, and EHA compensation works either way. Enrichment and fuel shutoff conditions can't be met without loop control in a KE system, though, but the ECU may still respond to the airflow meter potentiometer, which will provide enrichment information. Other inputs likely still active are altitude compensation, cold start valve (O2 sensor not active until warm anyway), and temperature sensors.

Steve

[locry]

thanks mr sbourg for all the info! appreciate it.

i'm not used to this injection stuff...