1987 ford rangers starter will not quit cranking

First use a socket to turn crankshaft pulley. Prove engine will rotate. If it does rotate; your engine isn't locked. Go to fuse box under hood, check fuses. Google how to use test light if you don't know how. They're cheap to purchase. Identify crank relay in fuse box. Swap it with identical one ie horn or ac relay. Oh! Check battery connection first. Should be tight. Turn on headlights? No have battery checked.

No, but the tach signal may help you determine if coil is getting signal to spark. If tach needle is moving when engine is cranking over, that means the coil primary circuit is being turned on and off, and that means the ignition control module is working.

Try turning the key just to on. Listen for the fuel pump to run and quit. try this 2 or 3 times then attempt to start . if this works it may indicate a leak in the fuel system. Hope this helps

Try quickly turning your key to the start position and back to the on/run position. Your truck is like mine, if you have a quick hand turning the key to start your truck it will start normally. Honestly that's the best solution. Hopefully I explained myself thoroughly.

Check for spark. No spark can be from the coil, igntion module, crank sensor. Have the codes check, this will at least point you in the right direction.

CHECK VOLTAGE AT STARTER BIG WIRE COMES FROM BATTERY, SMALL WIRE FROM IGNITION SWITCH , WITH TEST LIGHT CHECK VOLTAGE AT SMALL WIRE WHILE SOME ONE TURNS KEY TO START POS. IF THERE IS VOLTAGE STARTER NO GOOD. IF NO VOLTAGE CHECK IGNITION SWITCH AND SAFETY NEUTRAL SWITCH.

Check your battery

check fuel pressure.if not above recomended spec. replace fuel pump. for starting have solenoid 0n starter checked.

possible starter solinoid bad

Youll have to take it out and check the condition of the ring gear through the starter hole use mirror and torch if you have to.Before taking the starter out turn engine over by hand to a different position then try to start with key.Try this several times if it doesnt work first time Why was the original starter replaced.Im assuming the starter you brought was reconditioned or new Did you check that the battery is still ok?