My 1990 Chevrolet Truck isn't getting a spark... I've replaced the distributor & plugs, cap, rotor, coil, ecu, and everything... Still nothing

did it jump timing ?

Have you tried reversing the wire's on the coil ?

Check the compression on each cylinder. Also check for proper valve operation. You may have a flat cam lobe or bad rocker arm on either the intake or exhaust side which will give the rough idle you are experiencing.

First does the rotor turn when cranking engine?? possible timing chain is out or stripped gear..are you sure it has no spark??did you verify this with a high output spark tester ? did you spray starting fluid in the tbi unit ?

seems you,ve replaced just about everything,but i did,nt hear any mention of the coil?

This diagram is for 1998-1995 Chevy 6 cylinder 4.3L engines.
Your got the firing order exactly correct, at 1-6-5-4-3-2, but here's the thing to double-check:
The distributor rotation is clockwise (note badly rendered arrow in picture).





Since you probably got everything right, then you're left with really unusual/rare causes of
failure of the ignition system:
(a) rotor button misaligned/failing to make contact?
(b) rotor button not pressed onto distributor shaft far enough therefore failing to provide correct
proximity to distributor cap contacts when coil fires
(c) coil wire or contact loose/disconnected - press coil wire firmly down into distributor cap.
(d) distributor shaft of other damage caused during installation of rotor.
(e) spark plug wires defective from factory
(f) spark plugs defective from factory
(g) battery low - may need a charge to start
(h) ICM (ignition control module) failure - hook up your HEI (high energy ignition) tester, and
watch the quality of the spark on each cylinder.
(i) fuel problem? If spark is being properly delivered, its gotta be a fuel problem...
(j) distributor cap not screwed down flush to top of distributor? maybe just on one side?

Inspect the inside of the distributor cap - if there are lots of little metal bits all over the inside
of the distributor cap, then you know you have a misalignment of some type in there, and the
rotor and cap are destroying each other. normal operation will throw a quota of spark-ed off
metal bits inside the distributor cap, but since your cap is brand new, your attempts to start
the engine should have rotated the distributor so few times, you should see no metal debris.

Inspect the distributor cap contacts to see if any spark marks are more of less in the middle
of the cap's proper "contact zone". If not, you've diagnosed an internal misalignment, which
you know how to correct.

You've already eliminated the spark plug & wireset, distributor cap & rotor.
Sounds like your car needs a tune-up, specifically, the PCV (positive crankcase ventilation) valve, and/of the EGR (Exhaust Gas Recirculation) valve.

Components checked/replaced during a tune-up are:
air filter
motor oil
motor oil filter
breather filter
fuel filter(s)
fuel strainer
PCV valve
EGR valve
spark plugs
spark plug wires
ECM or distributor cap & rotor
cabin air filter
transmission oil filter
transmission oil
engine coolant
check all vacuum hoses and lines

Troubleshooting the no-start condition - from the 1990 Mitsu Mighty Max Repair Manual:

Priority Action Part Type -- Cause
1 Inspect Battery -- Battery Discharged or Faulty.
2 Inspect Battery Cable -- Corroded, Broken, Shorted or Poorly Connected Battery Cable.
3 Inspect Distributor Cap -- Distributor Cap Cracked or Burned.
3 Inspect Fuel Filter -- Clogged or Dirty Fuel Filter.
5 Inspect Ignition Coil -- Faulty Ignition Coil.
6 Inspect Wireset -- Worn, Damaged or Faulty Spark Plug Wire(s).
7 Inspect Spark Plug -- Incorrectly Gapped or Fouled Spark Plug(s).
8 Inspect Starter -- Starter Motor Faulty.
9 Inspect Fuel Pump -- Low Fuel Pressure.
10 Inspect Solenoid Switch -- Faulty Starter Solenoid Switch.
11 Inspect Fuel Pump Relay -- Faulty Fuel Pump Relay.
12 Inspect Fuel Injector Pressure Regulator -- Faulty Fuel Injector Pressure Regulator.
13 Inspect Ignition Switch -- Improperly Connected or Faulty Ignition Switch.
14 Inspect Starter Drive -- Faulty Starter Drive.
15 Inspect Fuel Injector -- Dirty or Worn Fuel Injectors.
16 Inspect Fuel Pump Strainer -- Clogged or Dirty Fuel Pump Strainerat.
17 Inspect Engine Control Computer -- Incorrect Operating Information Being Delivered and Sent From The EEC.
18 Inspect Fuel Tank -- Fuel Tank Empty.
19 Inspect Carburetor -- Carburetor Flooded or Faulty Choke.
20 Inspect Distributor -- Worn, Loose, or Incorrectly Installed Distributor.

That is indeed odd. I would suspect problems with the hi tension cables if this was not part of the ones you changed since the flow of current ends at the distributor. Check also other cables such as the ground. It is puzzling that all plugs would not have any spark. I would also recommend a scanner used to check for error codes given out by the car's ECU.

Does the 90 model still have the resistor and rotor button under the distributor cap? Have you checked for that?

assuming you the coil, plugs, cap, rotor and wires are good. check the cam sensor, If you have 12 volts to the coil using a 12v light tester. The cam sensor responsible for sending info to the computer telling it that the cam is turning, then the computer tell the coil to dispurse the charge/sparks to the distributor as distributor distribute the sparks to each plugs from the rotor of the distributor. Replace the cam sensor, it tend to go bad over period of time.