Thomas928

Hi guys,

1983 Porsche 928S EU

This is my first post here. Sorry for the long story, but I could really use some help diagnosing my issues

I bought a 'reasonably decent' 928s as a hobby/project car. It was running when I bought it (although the fuel mixture was pretty rich) and I am now doing small jobs on it one by one. I am by no means a trained mechanic, but I know my way around basic to medium stuff.

Next thing happened:

My car heater was constantly blowing hot air so I decided to take that as my next job to do.
I removed the console and cluster inside the car and I removed the air filter housing to see the hot water valve for the HVAC. Soon as I did that I could see some vacuum hoses not attached and some really old brittle ones. I replaced the brittle ones and I hooked up the other ones to the points they should be attached to. I also found out the whole airco build was removed from the car and found one vacuum hose not being attached to anything. this 'open' line was on the 4 way vacuum splitter near my brake fluid system. I plugged it so it wouldnt make the system lose the vacuum.

I then went back to the vacuum valve that arranges the hot water for the HVAC and saw that it was holding the wire of the connector that goes to the Kjetronic system ( underneath the fuel lines section ) was firmly wrapped (warping /choking the wire) on that heater valve, probably to keep the valve in position. I removed the tie wrap, unleashing the wire of the connector and went on with my work.

I then went back in the car and figured I could clean the ground point ( as per beginners stuff to do stated in this forum ) behind the dash cluster. I loosened the ground wiring and cleaned it up, and put everything back.

At this point I tried to restart the car, which was working perfectly one hour before and all of a sudden, it started, but running really bad, stalling after a couple of seconds.

I don't know why, and you can call me anything you like for it.... I got a tiny bit frustrated, decided to sin and change the fuel/air mixture on the K jet. I did not set a starting point and it is now in an unknown position. Believe me, I know how stupid that is.

So right now, I am at a point where I can try and start the car. It cranks, It fires for a second but then instantly drops and stalls. I tried to change the mixture a bit, and it starts every now and then after fiddling a bit with the mixture screw, but eventually it will stall again and it will go to the poinmt where I can start it, cranks, fires, but stalls again.

One thing that I noticed is that when I put the key in the ignition on, I dont hear the fuel pump. So I made a bridge with wires and a switch to activate the fuel pump. That also didnt happen. It still dies right after it fires.

Can anyone help me on diagnosing this? I have a vacuum tester coming in tonight to test all vacuum lines.

Could it be something in the ignition since I removed the cluster and worked in there?
How can I get that K jet tronic fuel mixture back to a working state?

Hope someone can help me out!

(and yes, I know I am stupid for tampering with the fuel mixture)

Jason89s4

I’m not responding to any mixture issue you may have , but it sounds like symptoms of your not getting fuel pressure to your motor as needed.
What you describe is likely the motor starting and running for a few seconds just off of the initial “squirt” provided by the cold start injector, but thereafter you are not getting fuel to continue running as designed. (Sounds like you do have spark since it fires for just a bit….so fuel is issue)
My experience is that with your situation the injectors are like clogged and need cleaning it replacement.
Try this simple test (best done with helper and it will tell you a lot and for cheap.
Remove the air filter and start as before, then spray Starter Fluid into the intake area under where the air filter was. With constant pulses of spraying starter fluid see if it will run. If it is fuel related/injectors/pressure you will be able to start up car as you have (cold start squirt starts it) and after that with a steady hand continuing to supply starter fluid you can literally run the motor until your can of starter fluid runs out!
try that and report
Also have you vacuum tested the Fuel Regulatirs and damper? They operate together off vacuum and if bad then fuel oressure will be an issue.

Thomas928

Hey Jason,

Thank you for responding and sharing your thoughts.

I have some extra questions, if you don't mind.

With spraying in the intake you mean the plate of the k Jet? ( as shown on picture )

Also, that wire that connect to the K Jet is all strangled up by that tie wrap. Could that also be a cause ( before I cut it open to check ) ( as shown on picture )

Jason89s4

Last thing first…ANY suspect wiring could be an issue. Fix and test all wires and plugs that look suspect.
yes, that is where you spray. You are mixing starter fluid with the air going in.

Thomas928

Hey Jason,

Thanks! Went to the shop for some quickstart and vacuum hoses. Replaced everything.

Then tried to start without help. Same thing. Fires up, then dies.

So I asked my wife to start the car for me and used the quick start like you described and yes. It starts and runs.

Now the weird part (for me at least). It keeps running. It just needs a tiny little squirt. So I had it idling up to the point where it was at nominal driving temperatue and I tried throttling a bit. Now if I do that gently, its ok and it just surfs back to a nice idling rpm. However if I let it go to 4000 rpm fast, it will die again.

So I tried restarting. When the car is hot/normal cruising temp, it will start. If it s cold it needs that little squirt...

I feel that I am getting closer towards a solution, thanks to you. However... not quite there.... any more advice?

Thanks!!!

mkhargrove

this is pretty similar to the symptoms i had on my 84 (usa)....bad resistor in the air flow meter. it would start and sound like it was going to run but it would die immediately. the check was simply to unplug the afm....if it's bad afm resistors (or probably a broken wire in the afm connection loom) it would start and run like crap. i'm not sure about the euro...does it have the same type of air flow meter?

Thomas928

Hey Kevin,

Thanks for your reply.

I'm not quite sure the MAf is the problem right now. I didn't really touch it and all I did was work on the car for an hour orso and it didnt start anymore after that.

Right now, I can get it running, but only if I use quickstart fluid in the inlet. If I do that, the car picks up on it and runs perfect up to the point where I start revving it.... then it stalls again...

Adding to the above: it really smells like gasoline.... I dont see any leaks or such in or underneath the car, but my wife is starting to complain when I enter the house after trying having it run for a bit :-)

Maybe its also worth mentioning the car has a WUR, and it looks fairly new and untouched.




Anyone? thanks!