I have a 98 chevy silverado 1/2 ton 5.7L motor. My truck will only start after I turn the key over and over to allow the fuel pump to run. I sometimes do it 10 times before it actually starts. After its on it runs great

check wires to pump,may be grounded;if not the pump is bad. quite sure its wiring

spray gasoline or carb cleaner into intake. If engine starts, it's a fuel problem. You have a bad (new) fuel pump or relay. Either no power to pump or pump is bad (unlikely but possible).

the fuel pump operates off the oil pressure switch the first 5 seconds upon starting. to test turn the key to the on position and listen for the fuel pump running. it does this to prime the pressure up and to stat the engine
if not heard replace the oil switch. the way this operates is when the engine reaches full oil pressure the computer shuts off the oil switch and turns on the fuel pump relay to continued the circuit to the pump

the truck has to have the basics . Spark fuel and compression in that order. Remove a plug wire from a plug either remove the plug or install a different one in the end on the wire and crank the engine with the plug laying on engine ground in good view and see if there's spark. Being you did'nt mention what motor is in the truck, desiel. 10 cylinder gas 8 cylinder gas 6 cylinder gas 4 cylinder gas I can only guess at what kind of engine were working on. The gas engines have spark plugs as the desiel has glow plug heating system and direct fuel injection. Silveradoo is a trim level and theres 1/2 ton 3/4 ton 1 ton and 1 1/2 ton versions. They all have fuel pumps and if they have more than on tank or a desiel they can have more than one. The gas engine v8 has troble with the ingtion and the module is the most likly for the cause of no spark but the mileage wasn't stated so I have no idea where to start. if it still is'nt getting fuel with the new fuel pump it's still possible that is'nt running or if it is its wired backwards and is pumping backwards. If the fuel pressure checks OK (above 50 lbs. that part shold work. Below 45 lbs they might run but they won't start. Compression has to be good 100 lbs or more on any engine. most chevy engines are much more in good shape.150 or even as much as 220. low compression and it was running OK the last time it ran sort of says the timing chain skipped as the compression normally does'nt go away quickly. The exception to this is overheating and racecar type blowups. some engines after overheating will have little or no compression and if started with added fuel and revved up they can unstick rings and or valves. and go back to normal. the reason for the overheating needs to be found as this happens again the motor might not come back to life.

will not start or will not turn over?

clogged air filter or faulty plugs or incorrect gap on plugs

The fuel pump inside the fuel tank might have a bad armeture or brush failure. Have someone crank the engine with the key inside the vehicle while holding foot on brake pedal and e-brake on.
Take a large hammer and bang on the bottom of the fuel tank while the engine is cranking. This should wake up the pump. This is only a temp. fix if the truck starts. That was a sign that the pump has failed and should be replaced.
Good Luck.

1985 1/2 ton delux. Wont start. New battery, wires, plugs. Alternator is good, tank is full, fuel and oil are good. Carborator is good. What could it be?

when you cut the key on do you hear pump run for a few seconds? if not then it is probably pump. try beating on tank with your hand while someone spins over. sometimes this will shake the pump and it will kick in. if this is case then you will still need pump because it WILL happen again. let me know

is your security light flashing? can you hear your fuel pump come on?