Quote Originally Posted by Peno67 View Post
One more question, The mixture screw has been tampered with. Is there a good starting point to begin with as I have no idea how far off the thing is?
Assuming the injectors are working (opening) at the correct pressure, you turn the mixture till they shut off and then turn it till they *just* start to crack open. This doesn't work with dirty injectors or a stuck fuel plunger so trying to adjust things when they aren't working properly won't get you anywhere. My guess is the mixture adjustment isn't that bad unless you already messed with it. You are running over-rich because the fuel plunger is stuck. The air sensor plate is mechanically balanced against the fuel plunger. As the plate goes down it pushes the fuel plunger up. If the plunger is dirty and sticks it won't come back down when the air sensor is released. When you have fuel pressure do you feel ANY resistance when you press on the air sensor plate? If not, that plunger is stuck and/or you have no fuel pressure in the metering unit. Once you get the plunger unstuck you need to get the injectors cleaned and tested. If you have a Volvo dealer nearby they may have an cleaner/tester. Or you can send them out.