sethrupenthal

Background:

Phase 1: aquired 1988 Porsche 924s in non-running condition. No crank, no start. Replaced battery.

Phase 2: after new battery and jostling loose wires under dash/fuse panel I have a crank, no start condition. It sounds like there is no combustion occurring at all. Just the starter turning the flywheel/crankshaft with seemingly no resistance. Tested for spark. No spark.

Phase 3: replaced ignition coil, plugs, wires. Have spark. Still crank no start. Still same sound of no resistance or load when cranking. Checked compression. Zero compression in all 4 cylinders.


Possible causes:
1. Worn piston rings. Would not be surprising on a car of this age and condition, but ZERO compression? On ALL cylinders?? Unlikely.

2. Blown head gasket. Also wouldn't be surprising, however any failed head gasket I've come across in my years of turning wrenches still generates SOME compression before leaking down - at least while cranking.

3. Broken timing belt. I thought I had a winner here until I pulled the cover off and discovered it was not broken.

4. Timing belt improperly installed. I'm leaning toward this as the most likely cause at this point. If the belt was installed with the timing marks in improper locations, the cam rotation would be consistently off, resulting in valves opening/closing at the wrong times and allowing any air to escape through the exhaust valve before the piston compressed it. (Or if the intake valve was closed on intake stroke, it would pull a vacuum).

Thoughts? Does this sound consistent with an abandoned and neglected 2.5 of that era? Any other possible/probable causes I may have failed to recognize?

Thanks!

Seth

BGMacaw

Very strange for sure that all 4 are down.

A couple of random thoughts -

Compression tester malfunction maybe?

The engine is an interference engine.
If the timing belt had broken on the previous owner while he was driving
the valves (at least some) were most likely damaged and rather badly I would think.
I recall reading a post somewhere a while ago where one guy lost all his exhaust valves and one intake.
If the previous owner put a new belt on thinking it was the only problem they would be sadly disappointed.

sethrupenthal

In the process of removing the timing cover and distributor cap, I found a broken piece of orange molded plastic. Ironically, right after finding this is when I pulled the distributor cap and the piece matched perfectly to the distributor rotor (which looks brand new). Clearly, someone has been in there to replace the rotor and I can only assume that maybe they re-installed everything with the cam 180 degrees off. Intake valves closed on intake stroke and open on exhaust. Vise versa on exhaust side. Also presuming the valves aren't toasted.

The more I take this thing apart, dropping a 460 under the hood seems much more rewarding. I found one locally for $275.