I have old carit still have low milest, The truck has know spark we thought it was the fuel pump but it not.what do you think?

Make sure the relay on the fender is getting a full 12v

Check all fuse and box they burn out and the bump could have blown a fuse.

If fuel injected- Central Fuel Injection, as I think it was, the electric pump should be in the gas tank. If still carbureted, it will have a mechanical fuel pump on the engine.

No one can diagnose any vehicle problems without the patient

You need wiring diagrams & a volt meter, to test the fuel pump
circuits you suspect being an issue

Was the old pump bad or never tested either?

The fuel pump reset button is commonly located in the passenger compartment behind a panel near the foot boards...passenger side and looks like a relay. The red button may be protruding and simply needs to be pushed back.

If u hear the engine cranking in the AM, the batt & alt sound good. If you don't get any engine cranking in the am you may have an electrical short draining the battery. Before u convict the starter u must make sure the battery has full power in the AM. (12V) & 12 V to the starter

Well, you need to check for spark and for fuel. To avoid wearing down your battery, I would put a charger or jumper cables on the battery as you do these tests.

You can test for spark this way. Pull a spark plug wire, and then insert either the end of a phillips screw driver or an old spark plug. Now, keeping your hands away from the metal, hold the screwdriver shaft very close but not touching an engine ground. Or, if you are using an old spark plug, touch the plug end to a ground. Be careful to have a very close gap to ground to avoid damaging your ignition system. Now have a helper turn the key to start the engine. If you see a spark jumping the gap of the spare plug or from the screwdriver shaft to the ground, then you know you have spark.

If you do have spark, then reattach the wire and try starting the engine again with a little starting fluid sprayed into the throttle body. If you don't have starting fluid you can also use a capful of pure alcohol or a very small anount of gasoline poured into the throttle body. Starting fluid is the safer bet. If the engine sputters and kicks over for a second, you know that the problem is fuel delivery to the throttle body, and it may be related to water in the lines (possible, but unlikely) or dirt and debris that clogged the filter from the low tank, or some other issue such as a bad fuel pump.

when low on gas the impuritys in the tank can clog the fuel filter, so if the fuel pump has air in it , it might not be able to overcome the resistance in the filter, replace fuel filter and try again

If it is not a fuel problem, then it has to be either not enough air or an electrical starting problem. Try starting it without the air filter in place. It could also be a bad plug or more likely a bad spark plug or coil wire.

when you check for spark check all cylinders u can use a regular spark plug and wire ground the plug end set the gap a little higher than veh calls for then yuoll know if it can have enogh to run all cylinders if you find only 2-3 firing thats still considerd no spark. hope this helps THUNDERBOLTZ