97 GMC Safari Cargo: engine turns but will not start

The first thing I would do is get some good fuel injector cleaner go by the directions on the bottle then take the blazer for a good run on the highway do this for a good while maybe a week or so and see if this helps. I have a 98 GMC Safari I also had this problem so I did the injectors and I also found out that my distributor was cracked and this created my starting problem, so good luck. Trial by error

check fuel pressur, filter and fuel pump...sounds like it isnt getting fuel

Check the fuel pressure

whats a safari GMC?? just shows you how much i know ---- never seen one but if it fits then your ok ,sorry but very rare machines here in spain ,now ask me about a renault or a peugeot

If your gmc safari cargo van overheats when the ac is on, your radiator and cooling system may be clogged and not working at peak efficiency.

Make sure your radiator cooling fan goes on as soon as you turn the a/c on.

Was the problem there before you changed plugs and wires? If not then it's something that you did, possibly crossed a couple plug wires. If the problem was there before you started and you are not getting a check engine light. Try disconnecting the exhaust at the exhaust manifold, just take the pipes loose, or if you can get them fairly easy unscrew the O2 sensor from the exhaust pipe. Try driving now for test purposes only, you may have a plugged catalytic converter. I just worked on a Suburban that had no power in fact it would barely run, that's what I found with that vehicle.

Had same exact problem, it was a bad coil. I could not duplicate "no start" problem with water bottle. Replaced coil and problem gone.
Note: There was a noticeable engine misfire at highway speeds on humid days. This accompanied the no start problem.

check crank sensor.

First thing on a diesel problem such as yours, would be FUEL FILTER. On GM diesels a clogged filter affects a diesel even more than on a gas engine. NOW if the filter doesn't cure your problems, I'm afraid tio say the injection pump could be at fault, and thats another story. Hope this helps