Engine issues

[900s]

Good day,

I am new to the forum, but hoping for some assistance.

I bought a 1990 900s a few years back. It was in great condition, but did not run. I tried about every thing I could find by searching the forums and to no avail. For the next three years I would occasionally try working on it again and never actually got it running. Meanwhile it has been sitting in my garage and still looks good as ever.

A couple weeks ago, with the help of a friend, I finally got it to somewhat run. We accomplished this by wiring the #15 on the coil directly to the battery. That will make it start and actually run quite nice. Until it warms up a bit (I think).
Then it will just shut off. I can then start it again. It will run again although not as long as the first time, and then shut off again. Repeat this until it wont start at all.

Let it sit for a few hours... and it starts right back up again.

Looks like it is running rich as plugs are wet and black.

Couple things I have done/confirmed:
Spark seems good even without wiring 12v to coil.
Have switched out CPS, EZK, CPU and ignition amp (EZK and CPU didn't make a difference, so I have the originals back in).
Changed out plugs.
Have checked for fuel pressure.
Probably missing some stuff here as I have been trying to fix it for a while.


Any help would be appreciated.

[GeoffR]

If wiring the coil directly gets the engine to start but it stops again after a period I would try replacing the coil.
you really aren't going to get to the bottom of the problem without wiring diagrams, you may need to look on eBay for those.

[900s]

Thanks for the reply,

One of the things I failed to mention is that I have swapped out the coil and the distributor cap, rotor and leads.

I actually have original Saab 900 service manuals at my disposal. Have looked thru the drawings a bit but no luck so far.

[GeoffR]

OK, I don't remember the ignition circuit but you need to start at the beginning by checking that each position of the ignition switch powers the expected circuits. I am sorry but without the wiring diagrams I cannot offer specific ideas.

OK I have the diagrams, easier than I thought to find them. Have you changed the ignition amplifier? It is a small box that connects between the coil and earth point. It doesn't like getting hot, when it does it cuts out, and the engine stops

.

It is located as shown below, just below and forward of the EZK