James_944

I pushed the plus wires home until they snapped into place. Also made sure they go around the distributor in the firing order on the cam tower.

One thing I forgot to mention is the fuel pump does not seem to pump when initially turning the key to position 1. I checked the pump (which is new) by jumping the DME relay and manually running the pump, that works.

Maybe the stall is the lack of fuel pressure if not running properly via the relay?

What about miss/back fire though?

Thanks

divil

The fuel pump isn't supposed to run until the engine is cranking/running.

Have you double checked that all sensors are plugged in - DME temperature sensor, AFM etc.? It might also be a big vacuum leak.

James_944

Ah ok that explains the pump.

ARM is plugged in ok
DME temp sensor. Is that on top of the cylinder head?

Vacuum pipes have all been replaced with new and I am pretty sure I have them all back in the correct place. I have followed the info here: https://rennlist.com/forums/924-931-...m-diagram.html

divil

Yes the DME temp sensor is on the head, at the front.

James_944

I replaced the wire for that as the old one had gone brittle and started cracking with the heat. I am sure I put it back as per the way it came off. I will double check in he morning as I am losing light here in the UK.

I think that vacuum diagram is correct and I am quite sure I have reconnected everything as the diagram shows. Interestingly when I was removing the old vacuum tubing I found some oddities such as the line from the temp sensor at the rear of the head was blocked off with a bolt inserted in the pipe.

divil

Not sure which line or temp sensor you mean...that description doesn't match anything I know of. There should be 2 temperature sensors on the head (one for the DME and one for the dash gauge) but neither of them have a line you can block off with a bolt...just wires.

James_944

http://workshop-manuals.com/porsche/...ons/page_2535/

There is a thermal vacuum valve at the rear of the head next to the coolant inlet at the rear.

This is the one that had one side blocked off.

James_944

OK here is my plan of attack.
Double check spark plug leads at both ends. Maybe take out plugs and check for any fouling, they are new so would be easy to spot.
Take off distributor - turn over engine by hand to TDC, check alignment with OT mark on flywheel window, fingers crossed it shows TDC at cam sprocket also. Check balance timing marks (although not critical) for a startup issue).
Check rotor points to Cylinder 1 at bottom right. If it does not worry lots.
Check for vacuum leaks around intake and hoses.
Keep fingers crossed I find something simple and can fix it.
Pray, not sure to whom, anybody who will listen.

James_944

Another update.
Distributor cap was a little loose, possibly even upside down, rectified that.
Rotor was loose, rectified that.
Moved to TDC by observing the camshaft timing mark.Checked flywheel TDC marking through bell housing window. OT seen on the mark. Relief, so all sounds good there.
Leads all checked and ok, from bottom right of dist cap being 1, I have the leads going 1-3-4-2 in a clockwise direction, as it should be.
Coil checked, no signs of overheating etc. Sprayed contact cleaner anyway.
Plugs are sooted, so running rich?
Cleaned DME temp sensor plug and socket.
Cleaned AFM plug and socket.
Resistance of DME temp sensor is 2.6K when cold.
Resistance from DME temp sensor plug 13 to ground is 1.16K

Now it does not start at all. It does not fire, I think I have lost my spark.
I am also not convinced I am getting fuel pumping as it cranks. If I jumper the DME relay all is ok.
Faulty DME relay?

konakat

Yes. If jumpering fixes everything, then it is just the relay or relay wiring.

plumbum

The relay could cause this, when mine crapped out I was able to pull it apart and see the crack in the solder...I used my key to scratch the solder which gave enough of a connection to allow my car to start... Now I carry a spare just in case.

I don't know if that would be your issue or not as it was trying to fire last time you tried but if somewhere near you has a relay you can swap it would be an easy test.

Tiger03447

Are you getting tach bounce? If not, check the reference sensors gap between them and the flywheel..8mm.

James_944

OK I have taken the ignition coil off and checked it over according to the Haynes manual
Primary is 0.6 ohm
Secondary is open circuit.

There is my first problem. Strange it did manage to fire up a little and now the coil is dead, although it is near 30 years old so maybe it just freaked out and failed.....

I was getting oil pressure and tach bounce on crank.

James_944

OK, just double checked against this:
http://www.porsche924-944.nl/manual/...on.htm#_05_015

Which gives me totally different instructions and resistances compared to the real paper book I have Confused.

Anybody know what the resistance should be on a coil?

Thanks

divil

This has the correct values:

That info is lifted straight from the factory manual.