Chevrolet Repair: GMC-Intermittant no start/dies, bad cap, fuel spray

Question
1990 GMC K2500 5.7L TBI 700R4
The engine will crank but not fire-intermittant, it will occasionally start and run with starting fluid. It has died at stop lights (hot) and not restarted. Retrieved code 34 and tested MAP sensor, found different ohm readings every try-r&r map sensor, same problem. Found corossion in the cap-every other post, cleaned cap & rotor-same problem. Replaced distributor, coil, plugs (not carboned up) fuel pump, fuel filter, tested for 12v at the inj-ok, after replacing dist engine fired and ran, shut down and wont restart. Tested for spark at the plugs-none, swapped control modules in the dist-no change, removed and inspected ecm connections-no damage or corrosion found, tested the coil-ok, power to the ign module, tested the knock sensor-various readings, removed sensor and bench tested-100k ohms terminal to sensor body. No diagnostics for the ESC, no fault codes.
What is my next step?


Answer
Hi Richard... you seem to be focused on the ign system... it does fire and run sometimes with start fluid... have you checked fuel pressure, does pump come on and run for three seconds when you turn key to on... if it does and you have fuel pressure look down throttle body when you crank it over...do you have a nice cone shaped spray of fuel... if you have a good cone of fuel spray, now check for spark....i have noted that you have changed the dist. did it come with a new ign module or are you useing the old one, check that the module doesn't heat sink...make sure it has the silicone between it and the dist where it is mounted. i also noted that you cleaned the cap and rotor not replace it  check for a bad cap or rotor...they are a known problem, also check the ign wires for resistance. too high means they need to be replaced....also check the wires that go to the ign module i have seen instances where they are frayed and cracked and not making good contact... also i know that this may sound nuts but have you checked to see if the engine is in time...check and see if you may have jumped a couple teeth on the chain and gears...if it is in time and you have fuel and spark it should run.....i know sometimes this stuff can drive you nuts....another thought check the ECM....hope this points you in the right direction.