K-Jetronic issue solved

Well done!!!

My friend would always say that:
"It ran well, when it left Maranello!"

 

I have a zillion miles on K-Jet and L-Jet cars going back to 85 and that part of those cars has never been a problem. Not ever.

If they don't work, it isn't the system/design/concept that is a problem, is't just a busted piece somewhere down in there that can be corrected.

 

I have owned several cars equipped with the K or KE-jet systems, they are generally a very robust and dependable unit. My experience has been that the main plunger in the fuel distributor getting stuck or binding via fuel varnish, stuck AVV or an out of adjustment WUR is about the only things that go wrong outside of worn out injectors which I consider a maintenance item. I am currently rebuilding the distributor in my Audi ur-Quattro which suffered from a binding plunger due to sitting for a long time. They are pretty simple devices but have very tight tolerances.

 

I would second what others have stated in this thread. Over the years I have tested, rebuilt, and calibrated many Bosch distributors (and WURs) and I have found them to be quite robust and particularly reliable in cars that are run regularly. For those cars that sit, varnish and other debris most certainly effect port flows in unfavorable ways. Where it gets interesting is when mechanics (DIY'ers and professionals) start making changes to the individual port adjustment screws in an attempt to compensate for disproportionate flows. This is why it is imperative that you have the appropriate testing equipment to calibrate post rebuild noting that if you put everything back together as you found it after cleaning (adjustment screw lengths, spring seat heights, etc.) the unit most certainly will be out of calibration. See post #8 in the following thread for some additional information which helps support the discussion: How to tell a fuel distributor needs rebuilding | FerrariChat

 

You are all right, who mention, that long sitting periods are mostly the one and only problem with these FI-systems. Over here in Germany in the 80s there were zillions of daily drivers Bosch K- or KE Jetronic equiped. Like the higher performing Vokswagen cars. And they were reliable cars if driven regularly or better said, used as a daily driver throughout the year.
I had cars with Bosch K-, L-, and D-Jetronic and the only source of trouble was the auxiliary air valve on the
L-Jetronic, which I replaced almost yearly. But it was just around $50.00 back then.

Best from Germany
Martin

 

I have an 85 308 QV GTS.

The car starts immediately and idles rough when cold (San Diego so not really cold)- running very rich. When warm it’s like a different car - responsive end quick (still rich).
A couple of weekends ago took it for a weekend ride and the fuel pump quit, cranked for a minute or so - let the Car sit and it started up again only to go to the next exit and quit again. Back to storage.

Today
Instant start. Goes up to 2000 rpm then degrades to 1500 rpm on its own where is stays for a minute or so. Add throttle end its responsive. Release the throttle and the ROM Slowly degrades to 500 and dies.

Application of the throttle during the sub 1000 rpm is slow to respond, then all of a sudden goes to 2000 at a jump (like a lag) and then degrades again to 500 to stall with no throttle override for the RPM.

here are the patients history in light of recent issues and recent issues.
Over the course of the year, We have rebuilt the CIS octopus, replaced the fuel accumulator and the fuel pump, new injectors and bushings, new plugs and wires.
Corrected and updated some wiring and connections to the fuel pump relay as well as installing the bypass relay (they call it the TR update -testarossa that has a Bosch Porsche 928ABS relay with a fuse now on the ECU plate in the back.

New distributor on one side the other checked to be working correctly. Coils are working properly
The AAV (under the expansion tank) seems to be working the WUR is an unknown.


Seems like an Air fuel issue or a fuel pressure issue.
HELP!!!!!


Fuel pump relay.

 

"Seems like an Air fuel issue or a fuel pressure issue."

I would agree. When you state that the 'CIS octopus' was rebuilt, am I correct to assume you are referring to the fuel distributor? If yes, did you or the rebuilder ensure balanced flow of all 8 ports after the rebuild as well as confirm system pressure to ensure the internal fuel pressure regulator was set appropriately? Was the control pressure regulator (WUR) adjusted as well? When I perform pre/post fuel distributor rebuild testing I recommend testing with the WUR in place to ensure cold control/warm control/system pressures are all within specification. See post #6 above along with the reference to additional Fchat content within that post which describes the challenges of rebuilding distributors without confirming balanced port flows post rebuild. Also note that after installing a freshly rebuilt, balanced distributor back onto the air flow meter an adjustment in the idle mixture control screw will likely be necessary given that the ratio of the air flow sensor plate/sensor plate lever to fuel distributor plunger will be set to the pre-rebuild fuel distributor flows. At this point I would recommend confirming what your AFRs actually is at start up and after warm up followed by confirming fuel pressures are within spec (cold control pressure, warm control pressure, system pressure). For reference, the 0438100139 distributor fitted to the 85 308 QV should have a system pressure of 4.8-5.4 bar while the 0438140132 WUR fitted to the car should have a warm control pressure of 3.5 bar. Note that cold control pressure is dependent on temperature and barometric pressure. Looking at San Diego weather currently (68 def F, 30.05 inHg barometric pressure), cold control pressure should be 2.0 bar. Hope this helps

 

Thanks @SeattleM5
awesome input despite my comical description of the CIS fuel distributor. I’m hoping to have a fuel system specialist/guru look at it either from Ferrari or Porsche racing. Let’s see who has the first slot.

From my purchase the car has always run rich and we couldn’t resolve it with the actions taken.
I know that these systems become bulletproof when dialed in and that this dial in process can be patience breaking.

Sanjeev