I have a1992 f150 i am getting fire,fuel and air but the truck still will not start. it will start and run as long as you hold the key in the start position but keeps starter inguaged

Hi,

Check the fuel line for clog.
Check the fuel pump
Check the fuel tank to see if there is water or dirt inside.
Check the carburator for good air flow and no clogs
Check the spark plugs and make sure they are all firing.

Hope this helps
Randy

Get a can of Starting fluid from the parts store and spray it into the air intake hose to the engine, if it fires up and stalls right away you have a fuel pressure issue, more than likely a defective electric fuel pump inside the gas tank.

Check all your fuses and make sure your battery has a good connection. Your fuel system may be starting to go out. Your fuel filter may be clogged. It might be a coolant sensor or intake air temp sensor. I would try to get it tested for codes and see if anything picks up on the test. This would narrow your problem down, hopefully. MAP sensor can cause this as well. I hope this helps you. Best way it the test though. Then you will know where to start. Start with fuses though. That is a simple and cheap fix, if that is what it is.

check for oxygen get a can of starter fluid take the hoses running into injector and spray couple squirts of that in it and try to start it if it starts you should have a bad fuel regulator

maybe fuel filter is clogged, or need a fuel pump.

I Have a 1999 ford f150 4.6 that back fires and is just running really ruff when idling alot of nack fire a sord of like a pulse going on what is my problem?

look for large vacuum leak. if you gotta spray fuel in there to make it run, then the air:fuel ratio is way unbalanced

So you turned the key just to "Run" and hear the fuel pump running (guessing elec pump)? Did you pull off a spark plug wire to check for spark? If no spark, pull the Distributor cap and check inside of cap, and rotor for damage, if ok, then the coil is bad, replace it. If you have spark at the plugs, have you tried Starting Fluid? (old school, go to AutoZone for this)

Can you hear the fuel pump run when you initially turn the key to on, I think they only run for about 5 seconds if the engine doesn't start immediately.
I think you have a fuel line full of air, but there is the chance you may have damaged the pump, because these are cooled by the fuel running thru them.

Don't know how deep you want to get, but there is a "shrader valve" on the fuel rail on the front right side (looks like a tire valve stem cap). Should be under the VORTEC shroud. You could hold this open, (like letting air out of a tire) while someone turned your ignition to on until fuel comes out. Once you see fuel, cranking it normally should be able to start the truck after one or two tries.
That should bleed the air out of the line quickly. Be very careful as you are dealing with flammible gasoline. Hold a rag over it so you don't get sprayed.
A fire extinguisher nearby would not hurt.

Gasoline engines need three things to run, fuel, air, and spark. Do you hear the fuel pump running from the outside of the vehicle for a couple of seconds when you turn the key to the on position? Check your fuses, on electronic fuel injection systems the engine won't run if the engine computer has no power. Spark: Take a spark plug out, connect the wire back to the plug, hold the threaded part against the engine block (hold this by the insulator, not the plug, you might get a bit of a shock) and see if there is a spark. Otherwise, just unplug one of the plug wires (either on the plug or the distributor), and hold it a small distance (1/4 inch to 1/8 inch) from where it was when connected and see if you can hear arcing. Air : Check your air filter /intake ducting for restriction preventing air from going in the engine.

I have put these in the most common order of solutions to a no start on a gas engine. From there, you can figure out which component is missing, whether gas, spark, or air, and go from there.