smcleod

Hi, I wonder if anyone has any information regarding a 1979 Porsche 928 4.5ltr V8. The car has been off the road for a long time. Got the car running after about half an hour, sounded good but was a little high on tick over. I then stripped the engine torque tube and back end out the car. The fuel tank was spotless inside, kept the original furl pump, replaced all the fuel lines, the fuel accumulator, fuel filter. When the engine was out I changed all the vacuum pipes on the engine timelining belt, water pump. All the usual stuff done then built the car back up but now the car is running very rich, wont tick over. Seems to be over fuelling. Suspected the metering unit K Jetronic part no 92811090600 and possibly the cold start. Tried 2 second hand parts but don't know if they were any good as the car I got them from wasn't running.
Wonder of anyone has any other ideas before I purchase some new parts.
Thanks,
Scott

Ducman82

K-jet = black magic. Try sacrificing a small animal. Even a Costco rotisserie chicken should work. :-). All the vac lines back to the original spots? Got spark?

BRB-83-911SC

I think you will need a set of CIS gauges (if you don't already have them) before buying any more parts. I'm sure some CIS experts will chime in here shortly with some specific things to check.

hlee96

The car was probably adjusted with high fuel flow to run at less than optimal conditions prior to your replacing all the parts that needed replacing. Now, with lots of new parts, the fuel is too much to run appropriately. Get a set of CIS gauges (I think Roger may still sell them, but I had to buy mine from Amazon when Roger was no longer selling them) and learn how to adjust the FD/WUR. If in doubt, send the FD/WUR out to be refurbished (not cheap!).

Good luck!
-Hoi

Mrmerlin

to adjust this system poroperly you should have a set of gauges to determine if the running pressures are good.
Once thats done then you can adjust the CIS mixture screw.
NOTE when the vacuum leaks are fixed the fuel will usually be very rich,
as someone probably adjusted the mixture to run with the extra air so now you have more fuel than it needs to run.

The CIS mixture adjustment screw is very sensitive and only a 1/4 turn or so will make a big change to the fueling.

You need a 3 MM allen wrench to adjust it and it needs to be about 12 inches long.
to lean it, turn the screw CCW about a 1/4 turn,
this should make the system run quite a bit leaner.

NOTE use your nose to smell for a reasonable mixture if you know what this means.
NOTE the Idle screw is on the front of the spider body to decrease the idle screw it CW.

STRIKEMASTER

I have an '83 S-2 K-jet Euro car...They don't like to sit...You really need CIS gauges, an AFR gauge and a "Color-Tune Plug to tune it. Check for proper pressure at the WUR, (System and Both Cold and Hot pressure.) Once that is set up, Turn the mixture screw closed( CCW ) then open it 9&1/2 turns. Close the Idle screw CCW then open it 1&1/2 turns...This,IIRC,is 'base-line settings' for 928 K-Jet... At this point it should run..(Mine did)..although it may be kind of 'rich'..Now the AFR can be adjusted with the mixture screw.. The book says always adjust from 'Rich' to Lean'..Every time you adjust the mixture screw, you have to change the idle screw setting also. They affect each other somewhat. The "BLACK ART" seems to be 'dancing back and forth' between mixture and idle screws till they are both 'sweet'.. The "Color -Tune Plug' comes in handy because it lets you see the fuel burn in each cylinder---White is too lean; yellow is too rich; proper 'burn' makes a "Propane Blue" flame...Because you can check the 'burn' in each cylinder, a clogged injector, (I had several) shows 'Lean burn'.. I had 3 partly and 1 fully clogged injectors. I could have played with mixture and idle screws all day and it would still have run like crap. LOL K-Jet injectors are fairly cheap, so I replaced all of them..Your Fuel distributor should have non-adjustable fuel ports, like mine...That takes "8 levels of complication" out of the process....It's almost like tuning a guitar: Tensioning one string changes the pitch of all the others..So keep at it, it just takes time to get it right.

jpitman2

Try to find an affordable copy of Watsons book on Bosch injection - very good on CIS, and its trouble shooting.
Check the fuel delivery rate is in spec - disconnect fuel return line at cam cover, run a hose from engine side into a container, bridge pump relay for 30 secs - should get around 1350cc; if not, suspect pump, filter or all the lines involved.
Get the gauge set, fit as directed at the WUR(warm up regulator). With tap closed you should see 65-75psi; tap open , cold -10-25psi; fully warmed through ~45psi; warm psi more than 55 will give almost no power. Usual problem is WUR clogged, holding control psi too high - suggest you load fuel with Berrymans or similar, bridge pump and allow fuel to circulate for several hours to try to dissolve sludge out and carry it to filter. If control pressure is high(based on gauge readings), follow Watson on troubleshooting to find the blockage - if fuel arrives at WUR, but doesnt come out much, WUR is blocked; if fuel comes out of WUR, but doesnt arrive at tank return hose, problem is in lines in between. Be careful - have a fire extinguisher handy! Dont mess with mixture adjuster until all pressures are in spec, then SLOWLY!
The injectors can be tested for spray and opening pressure readily - many 911s use fucntionally same units. Short MB brass units are cheaper and available.
jp 83 Euro S AT 57k