Not Starting... 1991 Volvo 240, B23F

[pete77gg]

Hey all. 1991 Volvo 240 Base Automatic w/ Original/B23F 4cyl Engine. It died on me 3 weeks ago. Battery was discharged but good and belts had been squeaking for a day or two. Got worse and just before dying due to the battery (lights went dim etc.) squealing. Checked belts & alternator seemed too lose. Tightened (over tightened??) and when tried to start, was turning over and about to catch but emitted a loud screeching, then a single backfire where I then cut it off & stopped trying immediately.

Took alternator belt off, all other pulleys ran fine, no noise when turned over for a few turns.Tested Alternator, tested good. Replaced new bushings, new belts and put good alternator back on. In doing so, inadvertently pull the what looks to be the oil pressure sensor wire from it by mistake. (Know I need to fix but figure one thing at a time & it shouldn't affect the alternator/screeching & now no start- is this correct??) Try to start & now turns over great-no screech, no backfire but it just keeps turning over without any sign of catching. At this point know it's not alternator/starter/battery. Before, fuel pump (in tank) was kaput but ran (hummingly) by Main pump (& was on my list to replace asap.) Replacing the in-tank later in week to eliminate it as the culprit but I don't think it is (as ran fine before whole situation). So....

If it is not the pump (both working eliminating fuel supply issue along with starter & charging issues) could the oil pressure wire being disconnected be a possible culprit? If not, where should I go from here? (Plugs are less than a month old, ran fine when changed) and Dist/Cap/Wires are relatively new & look to be in good shape. Possibly timing belt (the single backfire?) off or jumped tooth? If so, what would be a reasonable cost at a local shop to do this? Is it a possible DIY for a shade tree mech.? Thanks for the answers, I am just frustrated & stumped on this one. All advice welcome.

Pete