Does not start

Even with a new pump its important to check fuel pressure and flow . Low pressure fuel pressure regulator stuck open or fuel pump faulty . Low flow blocked fuel filter . if the above is all ok. Back probe injector with led trouble light , light will glow while motor is turning over. if not check fuses , if ok check injector cable back to the ECU for bad connections .

• too high fuel pressure. 30 ok 60 bad. PSI
• leaking injectors
• ECU injector driver shorted, turning on injectors full time
• injector drive wire shorted to ground bad wiring.
• ECT stuck at -40F (alaska temperature) USE a SCAN tool.
• MAP sensor vacuum hose/pipe clogged (ECU thinks your are going up hill all the time and floods.
• The scan tool can check each , but not fuel pressure.

that is a start,

may be but bleed the air out of the fuel lines first

Thee are a couple of things left to check. One is to hook up a fuel pressure gauge to the fuel rail and see how much pressure your getting and compare it to specs. It maybe getting fuel there but not enough pressure. To see if the injectors are being pulsed you wil need a set of noid lights. You will unplug an injector and plug in the noid light. It will flash everytime that injector is pulsed. If it never flashes your injector drivers on the ecu are bad.

1 Inspect Battery Battery Discharged or Faulty. 2 Inspect Battery Cable Corroded, Broken, Shorted or Poorly Connected Battery Cable. 3 Inspect Distributor Cap Distributor Cap Cracked or Burned. 3 Inspect Fuel Filter Clogged or Dirty Fuel Filter. 5 Inspect Coil - Ignition Faulty Ignition Coil. 6 Inspect Wireset Worn, Damaged or Faulty Spark Plug Wire(s). 7 Inspect Spark Plug Incorrectly Gapped or Fouled Spark Plug(s). 8 Inspect Starter Starter Motor Faulty. 9 Inspect Fuel Pump Low Fuel Pressure. 10 Inspect Solenoid Switch Faulty Starter Solenoid Switch. 11 Inspect Relay - Fuel Pumpat Faulty Fuel Pump Relay. 12 Inspect Fuel Injector Pressure Regulator Faulty Fuel Injector Pressure Regulator. 13 Inspect Ignition Switch Improperly Connected or Faulty Ignition Switch. 14 Inspect Starter Drive Faulty Starter Drive. 15 Inspect Fuel Injector Dirty or Worn Fuel Injectors. 16 Inspect Fuel Pump Strainer Clogged or Dirty Fuel Pump Strainerat. 17 Inspect Engine Control Computer Incorrect Operating Information Being Delivered and Sent From The EEC. 18 Inspect Fuel Tank Fuel Tank Empty. 19 Inspect Carburetor Carburetor Flooded or Faulty Choke. 20 Inspect Distributor Worn, Loose, or Incorrectly Installed Distributor.

You have fuel flow but the question now is are the injectors pulsing. Given the year of the truck my gut says your ECU, Engine Control Unit, has failed. Mitsubishi had issues with the capacitors in their early 90's cars, trucks SUVs. I have been thru this with two monteros and one 3000GT, very common. To check your injectors rent a set of NOID lites from Autozone our such. Remove an injector plug and itstall a noid light. Turn the engine over, if no flash, no pulse. Remove the ECU and carefully open it up. Look for the capacitors, there should be 3, look under the capacitors on the board; if there is a grease like substance, often time it has a green hew to it, then the capacitor(s) have failed. It may be possible to replace the capacitors or simply purchase a rebuilt ECU. Be ceratin the MD number matches on the new unit.
Please let me know your results and if this had assisted you.
Thanks, Tom

fuel rail preasure rgulator valve may be faulty

You may have a defective fuel pump relay which is mounted near the center of the fire wall area. Also check for any securty lock out or problem. If all passes ok, then check the fuel pump for pressure at the fuel rail.

actually it sounds like your crank position sensor may be faulty.

Top candidates for this problem are:
Clogged Fuel filter
Faulty Fuel pump
Clogged fuel injectors
Dirty / worn spark plugs

Of these, only the clogged fuel injectors are likely to respond to a gas tank additive, and even then you need to get the right kind of additive.
If your fuel filter has not been changed in a while (couple years), start with this. It is fairly easy to change. The fuel filter is under the car near the the driver's side rear door.
If this problem started "suddenly," then the fuel pump might be the culprit.
Fuel injector / spark plug issues are not likely to stop the engine right away, but would tend to cause it to miss cylinders, idle rough, or start rough.