My friend's 964 has a fresh fully restored engine.
However, it just briefly fires when cranking, and stops after one or two seconds. It is possible to fire it up if we work the accelerator, but it runs very rough and it does not sound good at all.
Since it runs, (but barely) the ignition must be working, unplugging one distributor at a time makes it struggle even more, but theres no difference between them
If we unplug the flywheel sensor it does not start at all
Resonance flap and other intake actuators seem to work
Fuel rail pressure is over 3 bar
Injectors are new and getting the proper pulses
We have used a different intake air flow meter, but with the same result
We had no oscilloscope available, and have not had the chance to see if the distributor Hall sensor is OK
Motronic DME, no fault codes
Any tips?
Thanks in advance!

Cheers,
Tore

 

Very interested in the findings here as I'm chasing down a starting issue with my fresh rebuild.

 

Can you confirm that the idle microswitch is engaged when you are starting the car?
If you get it running, is it only rough at idle or all through the range?

 

I can have the switch checked.
It does not run at idle at all. Just briefly rev up as normal when starting, but dies instantly before reaching idle.
We are able to keep it sort of alive if we work the accelerator when starting, but runs very rough. No shooting though, but some smoke, maybe unburnt fuel.
T

 

On my car the rebuilt injectors had sat after cleaning and they were seized, 100%. Maybe your new injectors are partially seized? The next thought is fuel pressure, I would attach a gauge that lets you see where pressure is cranking vs running. You can do the test in the factory manual and jump the relay to check pressure without actually cranking the motor over.

I'm guessing it wouldn't run with the distributor 180deg out but check that nonetheless.

 

T

The reason was that I do not have a hose or plug on this pipe that sits on the intake