Pulled it in the garage last Saturday, running well. Sunday - won't fire. Almost seems to catch on first crank after sitting for a while. So far, I've swapped relays around (fuel pump, LH, EZK), and jumpered the fuel pump relay pins. Fuel pump is working, still no joy. My suspects are cps, temp II and LH, just not sure what I need to do to test these or what else I'm missing.

 

Got spark?

 

http://www.jdsporsche.com/fault%20find.html

 

First pull the hoses off the dampers and the FPR remove the aircleaner to get to the rear units smell the vacuum lines if any smell like gas then all three of these parts should be replaced .

Remove both coil wires and inspect the ends for corrosion,
and make sure the wires are not rubbing on any part of their run,
if they are rubbing then the wire may be damaged and should be replaced

if no gas smell, then hold the pedal to the floor and crank it for up to 1 minute till it starts,
from the description you may have flooded it by starting it and moving it and then shutting it off ,
the engine never got to operating temperature/.
the plugs got fouled.

NOTE the early LH/ EZK computers dont usually fail,
usuall suspects are MAF,
and temp 2,
and O2 sensor,
along with the crank sensor,
and the TPS short connector wire with a broken connector, cause running issues,
as well as the FPR and the dampers leaking

 

Sounds like it may be flooded.

Foot to the floor, hold it there, crank.

 

Similar experience. 1987 S4. Turned out to be the brain.

 

87 and later computers need a rebuild once in their lives
84 Euro , 85, 86 computer dont usually suffer the same

 

Hey MrMerlin. Is that a guarantee that it will never happen again?

 

Check the battery? Just replaced mine today.

 

Depends where you had your brain repaired.


85/6 seem to have a flooding problem when started and moved a short distance, like on a driveway.

They also seem to have an issue with either a short or a ground fault within the main engine harness. We've seen 15 to 20 guys experience random no start.

So, the key here is it tried to catch. If so, its flooded.

Doesn't address the root cause, just gets it running. Nobody has addressed it yet, based on my 5 years of reading here, including me.

Regarding the harness problem, observe as I struggle. After this video I moved the harness 50 times. It has never repeated the problem, but the problem had plagued the car for months.

 

If your tach needle bounces/moves at all then it's possibly flooded. Pull a plug and check.

If the needle doesn't move, replace the CPS

 

Is this %100 for certain? I don't recall mine ever moving while cranking.

 

It should move a little on them while cranking yes

 

IIRC the tach will only bounce on the 1987 and newer cars when cranking.

Chris to answer your question ,
I think its a combination of a few things that go bad to cause the rich condition on the 84, 85, 86 cars .
In no particular order
A worn ISV they are a wear item,
the MAF going out of spec, though it can be readjusted
the O2 sensor, replace it as well as fitting fresh MAF.
The TPS short wire connector fails at the water bridge,
The temp 2 sensor.
The dampers and FPR
The ignition wires and coil wires .
The CPS connector
The grounds


I have done a few of these early cars where most if not all of the parts listed were needed to bring back a solid running engine.
Also had a few with damaged computers most likely from jumping the car due to weak battery,
or running the battery down because the engine wouldnt start,
and of course the bad ground connection in the hatch

 

Wiring is the same for the tach from 85-88 and it bounces on all that I've done.