White Electrical Box

Can you post a photo of the WURs and fuel distributors (and their generally associated plumbing)? (Might give a clue if things have been modified.)

Is/are there any O2 sensors mounted in your exhaust system?

 

That ballast resistor has me thinking it is a keyless entry device or perhaps rudimentary alarm of sorts, using a different value resistor as a coding device. Maybe I'm all wet.
Where do the wires lead?

 

Looks like an old 'D.C. Johnson' aftermarket O2 sensor controler

 

With Dave mentioning the brand name, I was able to find some pictures that I had previously saved (although the connector arrangement seems a little different, but maybe they did a couple of different versions as the physical box and the bit of label remaining sure look the same):
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Unfortunately, I've got nothing else -- and I would've guessed that you'd need two for a 400i (since you have two WUR), but don't know that for sure (as they may have done some unusual/creative "replumbing" ).

 

Common finding on the BBi's that were 'slid through' EPA at the time.

I have some old ones on the shelf that have the same connectors as photo'd but have a Coax plug for the sensor input in place of the 2 gray wires

 

What component on the K-Jetronic system in a 400i is subject to electronic control? I'm a rank beginnner on the subject, but I am not aware of any component which is electronically adjustable.

 

Here's a shot of an aftermarket system as implemented on a V8:
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They add a frequency valve -- i.e., an electrically controllable leak -- (and plumbing) that the aftermarket ECU controls (based on the O2 sensor output) to alter the control pressure (and, therefore, changes the amount of airflow metering plate deflection and the slit opening size for a given amount of air entering the engine). It can't be the fastest responding system in the world (with a lot of heavy moving parts) -- unlike the real "CIS with Lambda" systems that alter the lower chamber pressure (and the pressure difference across the slit) to change the amount of fuel delivered for a fixed airflow metering plate deflection and fixed slit opening size (no moving parts).

That's why it would be interesting to see if there is/are frequency valve(s) + plumbing added on Greg's 400i in a similar fashion.

 

Please have your grains of salt ready as you read my input. But these things I know: the K-Jet system meters fuel flow to the injectors by means of a piston inside the fuel distributor. Each injector line originates as a slit in the fuel distributor. As the piston rises in its bore, it exposes these slits to system fuel pressure.

Air flowing into the intake passage causes the piston to rise and to add fuel to the fuel-air mixture. But the K-Jet also uses the fuel itself, as a hydraulic fluid, to control the movement of the metering piston. This *control* pressure is introduced into the top of the fuel distributor, at the center of the casting. In your first photo, you can see where the control pressure line goes into the fuel distributor.

Higher control pressure pushes the piston downwards, decreasing slit exposure and leaning the mixture. Control pressure is controlled by the warmup regulator (WUR). The two plastic lines in your first photo lead to the WUR. The WUR has a valve which is at its minimum opening when the engine is cold. This allows the lowest level of control pressure, making the mixture rich. As with the choke on a carburetor, we need a richer mixture when the fuel is cold because cold fuel doesn't atomize properly. The WUR has a bi-metal strip inside, acting on the valve. This strip is heated by engine heat but also by electricity. That's why there's a wire attached to the WUR. As the strip warms up it bends down and opens the valve. Control pressure rises and exerts downward force on the mixture piston, decreasing slit size and leaning the mixture.

Here's where the grains of salt come in: I take it the system on the Mondial V8 has added an electronically controlled valve to one of the fuel lines that's connected to the WUR. This would allow electronics to reduce the control pressure beyond the WUR's base level. Reducing control pressure enrichens the mixture. This is generally bad for emissions, but good for power and to protect the engine from damage. OTOH, if you set the base level of the WUR's output to any artificially lean extreme, you could then use an O2 sensor and an ICU, acting on this valve, to enrichen the mixture to a safe level, while also minimizing emissions.

Unfortunately, I don't see such a valve in either of the two plastic lines running between your fuel distributor and your WUR. Again it's grain of salt time, but this suggests to me that, if your car was equipped with such a valve to federalize it, it's no longer there.

 

Have to agree with Bill that I don't see any obviously non-stock parts and/or plumbing modifications in your 400i K-Jet system photos (but I only have the 400i SPC for reference -- if someone knows where the 400i WSM is available online, please advise).

PS Next oil change replaces those Fram PH2804-1 oil filters with Baldwin B253

 

I was re-reading my Bosch fuel injection books today and I need to correct my previous post. When I was writing it I was thinking the WUR sits upstream of the fuel distributor, and that its action is to open its valve to apply additional control pressure to the top of the mixture control plunger (piston). In fact its action is the opposite -- "180 out" to coin a phrase. The direction of flow is from the fuel distributor to the WUR and then back to the gas tank. The WUR operates by bleeding control pressure from the fuel distributor. When its valve opens it bleeds off control pressure, allowing the plunger to rise in its bore and enrichen the fuel:air mixture. In a cold start, the WUR's valve is fully open. As it warms up it closes the valve and bleeds off less control pressure. Sorry for the confusion!

 

Not having read your story in the other thread, and not knowing what problems you are chasing.....

IF the Johnson system is still wired in and the O2 sensors are essentially dead from years of not regulating the mixture and resulting rich running, and then you re-make the connections putting them back in control of the mixture..... Yes, I would expect it to die at idle on occasion.

The power resistor, non shielded wires coming from the far right side of the Johnson box..... the list of reasons why this might not work is far longer than the list of reasons for it to work! When this was done initially, the intent was to get a stack of papers and a sign off. Very few were done with the intent of these bits remaining on the car for decades. The DC Johnson system was really a very well built, simple system and the ones I have on the shelf are still functional.

If you intend to make the O2 system functional again, may I suggest you start over again with a used Bosch Jetronic box from the 3x8/Mondials, and use shielded Coax wiring. Steve has very nicely documented the entire Jetronic system and the install would be simple, fairly inexpensive and could easily be made quite functional. If you intend to restore the Johnson system, be prepared to be chasing ghosts until all of the wiring and components are renewed.

 

Just my two cents. Remove the Johnson box and all of the attendant wiring and non factory parts. The system was not designed to run with O2 sensors. Yes, it can be made to do so, but why would you want to introduce one more thing that could potentially cause problems? Your car does not have a "check engine" light. So, unless you are going to add a wide band oxygen sensor with a guage to go in the cockpit FULL TIME, (actually 2; one for each bank) how will you know if the thing has malfunctioned and is creating a chronic lean run condition at cruising speeds?

Just put everything back to factory specs.

My daily driver is an old factory turbocharged BMW 745i. I bought it out of a salvage yard with most of the engine in the trunk back in the 90's. It had a Johnson box on it at the time, but I elmininated all that stuff. On the motronic, I believe the box was wired into the coolant sensor. It simply bypassed a bit of resistance when the O2 sensor was reading rich, which would make the signal to the ecu read as if the car were still a bit on the cold side, and vice versa for when it was lean, i.e. add resistance to that reading. I may have thow backwards, as I haven't actually looked at the resistance values in a few years, and can't remember off the top of my head. Last thing you need on a turbo car is constant lean running. Again, no "check engine" light. Might not know it until there is a hole in a piston. Then you will know it.

Again, just my 02 cents.

As long as you already have the bungs welded in for the O2 sensors, you might want to go ahead and add the wide band sensors and guages. Great car tool to have.

Lynn

 

Those are a stock part of the Bosch system -- they are the cold start injectors that give an initial squirt of fuel at cold start-up to add enrichment. I think it unlikely that they were unplugged as part of the DCJohnson system instructions, but once you get the CD you'll be able to confirm/deny. More often, they get unplugged as a "band-aid" fix to a warm restart problem caused by a bad Thermo-Time Switch (wrongly still squirting the cold start injectors during a warm restart) or if the WUR goes wacky and the cold control pressure is way out-of-bounds.

Once you get the CD, you should definitely do an "inventory" to determine just what you've got (and how it is connected), then decide next steps. Can't see everything in your photos, but it does look like you just have a stock system that may need some TLC. Have you ever tried following the wires from the O2 sensors to see where they go? Still think that you'd need two DCJohnson boxes on a 400i if you have two O2 sensors (unless they made a "2-channel" box)...

 

Better to test it before replacing it. Item 38 (Ferrari PN 113980) here:

http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=3282

http://www.ricambiamerica.com/product_info.php?products_id=192782

but better $-wise to buy it using the Bosch 0280130220 part number from a non-F part supplier