Engine is a 4.3 . Fuel psi with key on is 62-63 lbs and 65 psi when cranking . Not sure how or where to block off return line to check that way , fuel psi. does not bleed down after 5 mins. or so . I also replaced the ignition control module today and another dist. cap , still won't fire . I am checking the spark at the plug wire with a plug in it and it sparks fine so rotor must be spinning . Also tried carb cleaner down the butterfly today and nothing . It has plenty of power when it was running so the engine is not low on compression from to many miles on it . What about a stuck open EGR valve ? , running out of ideas here and going crazy . Dave