My 1987 Nissan D21 SE V6 all of a sudden won't start. It will crank but no fire. I've had the coil and module checked and they're good. HELP!!

There are some ideas in the link, but really you need an auto electrician with a pro-grade scan tool computer to diagnose DTCs and Communication Codes, plus it can test all the sensors and engine management modules.

https://www.google.com/search?q=1997+nissan+pickup+crank+no+start

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It could be the fuel system.
It could either flooding or starving for fuel.
If injectors are fouled badly it will wet the plugs and not fire.
If plugs are pitted that makes it easier to flood. (check plug tip condition, check all plug wires and boots are good)

If it is starving -- fuel pump weak (going to fail).
Need to test fuel pump pressure.

check the fusible links near the battery. There are 2 coils. It could be the coil, or power transistor for intake or exhaust. It could be the crank angle sensor. Check the ground connections really well also

likely to be a faulty crank shaft sensor.

Check for a blue snapping spark on 2 or 3 plug wires(or all of them). If you get good spark, then ignition is likely not the problem. A weak or sporadic spark could be a bad coil or coil pack, or a bad ignition module (the ignitor).Check the coils with a volt-ohmmeter per the specs for your car. The ignitor can be tested at a parts store.
If spark is good, check fuel filter, fuel pressure, check timing marks on crank pulley and cam marks, Try a little starting fluid in the air intake and see if it runs for a moment. If so, then it's likely a fuel delivery problem. If no change, then it's likely an ignition circuit problem.
Good luck.

Sorry about the late answer. Was in the outback (I live in Haiti).Did you check for power to the coil? This should be the first step. If power then check the distributor (the models we've here have electronic distributors with one coil).

Sounds like you changed the part that failed but did'nt change the part the caused the part to fail. the spark plgs wear out and need more power to fire as they wear out as do the old plug wires 87 is a long time ago and some are still running with the orginal parts (their that good) change all the parts at once ( plugs , wires , cap and rotor aand now again another coil) and you'll be back to going. remanber that low voltage will kill everythig and some starters will crank when the voltage is too low for anything else. fuel pump and the spark need good voltage to run and the starter may still turn the motor at very low voltages. check the battery and the charging system. You may try to just jumper to another car ( so the voltage is known good) and if it runs OK you are finding and testing battery and charging system parts.

you said you repl dist cap that means you don't have a crank sensor you have electronic ing module. remove your elec ing module have it tested most auto parts stores could test your module, or check your coil at the neg terminal. should have power. if not you lost your primary volt from your batt.your secondary power is coming from your electronic ing module from the module to the pos terminal on the coil, when the eng cranks,from the coil to the dist cap , from the dist cap center to the rotor then out to the plugs,this all happen pervided the timing belt or timing chain is ok. the cumbustion chainber needs 3 things , thats fuel, air, and spark.

early electronic ignition model i think if my oldtimers memory is correct ,try changing the ignition module ,i think it either under the coil or inside the distributor

the 3 coils are mounted to the ignition module and as long as the sensors that signal the module to fire the coils individually are working I would try a module especially if all 3 coils are not firing..also if you have an ohmmeter for checking electrical resistance, the spec for the coils are 5000 to7000 ohms, measured between each coil from tower to tower (ie) #1and#4 2+5 and 3+6 any more than that and the coils are toasted..lol hope this helps also check the spark plug wires at each end maximum resistance is no more than 1000 ohms per inch,,,good luck