Hi,

I’m responding to your question about a P1800.
I do not own one, nor, do I know much about them.
My experience with one was during an old car show held by local enthusiasts.

Other than popping my head over a fender of that one that may have been” a 1974 model that’s it.
He said it had fuel injection and he had a problem with it just shutting down very randomly.
I don’t believe or remember that if it was an early K-Jet model or not.
I discussed with him the possibility of it being a very early ECU module that needed be broke open and it’s solder circuits looked into and maybe a transistor or capacitors revamped.

If I were you making more posts on the 1800 section of the Brickboard it might get you more results.
You have to be willing to talk plentifully and steadfastly to get the interest of those of whom are really into their old cars.
I see you are new to the Brickboard with your sign in name on the 1800 tab back in June.
Time does slip away quickly even without the issues you mentioned.
The same procedures would go for any other forums you might find to use.

The only way I can help you is working with the basics of diagnosing and some methods to do that.
Same goes for your 1993 240.
The voltmeter is a good start with no matter what you are working on.
The rest has to come to doing research in manuals that cover those components used in a particular model and years of on going Volvo’s entire production lines.

I mostly hang out on the 240 section and stray over to the 900’s when things are slow and I’m not quite so slow. (:-)
The two models shared lots of components together around the mid nineties and the 1993 is unique in certain areas as I’m finding out.
If you look up above in this thread, to Art Benstein post, you can see where he supplied an illustration of the changes in the last of the three years of production and look the 1993 was still in progress!
This is why I peek over to the 900’s.

Keep yourself alive on the BB and both your cars will survive!

Phil