I finally decided to give this truck one more look before hauling it to the salvage yard. Truck cranks but has no spark.

Parts Replaced so far:
crankshaft sensor
camshaft synchronizer & sensor
PCM


Vehicle has factory non-chip key anti-theft system.

Test results:
50/50 test- no start.

in-line spark tester- no spark while cranking.

injector has 12 volts- key on, but no pulse while cranking.

fuel pump- primes with key on.

Coil- 12 volts key on, drops to 10 while cranking.

CEL- on with key on, goes off for approx 3 seconds while cranking then comes back on.

RPM monitor- reads 186 rpms while cranking, then drops to zero in about 3 seconds. RPM measurement is from OBD device. (Onboard tach doesn’t move.)

PCM pin 103 to B- has .6 ohms key off.

PCM pin 97 to B- has 12.1 volts key on.

CKP pin 21 to B- has 1.55 volts DC key on.

pins 21 & 22 at PCM -has .5 AC volts while cranking.

CKP at sensor - .5 AC volts while cranking.

CKP at sensor - 660 ohms resistance.

Ignition on column has lots of play.

Crankshaft and harmonic balancer seem solid with belt on.

I feel like the the PCM isn’t grounding/ungrounding the coil harness wires. Can this be tested with a noid light and wire clips? Or I have a broken wire or ground somewhere in the system. Any thoughts or ideas would be greatly appreciated. My son turns 16 in a few weeks and would love to have this truck.

 

Yes, you can unplug the 4 wire coil pack connector and put a put a test light or volt meter on the red 12v wire and any one of the 3 ground wires on that connector
Then crank the engine, light should flash, or volts should go up and down if PCM has detected you are trying to start engine, i.e. Crank sensor sending a timing pulse

There are 3 separate coils in the coil pack, and unless the 12v wire inside the pack failed there should be no way for all 3 coils to stop working, 1 maybe, which wouldn't cause no spark, just misfires after startup

From your tests the spark should be working
But the drop to 0 RPMs is troubling and most likely the cause of no spark

The crank sensor reads a tone ring on the crank pulley, it has 36 teeth minus 1 tooth, so 1 tooth every 10deg, for 360deg, and 1 tooth is missing which matches up with #1 piston at TDC
This missing tooth is how PCM times spark and injectors
It "sees" each tooth, they generate the AC Volts, then it "sees" the gap which gives the other teeth meaning, i.e. 10deg after TDC, 20deg ATDC, 30deg ATDC, ect................
Give the tone ring a good look, 35 teeth in good condition and one missing tooth
If a tooth is chipped then there would be TWO missing teeth so PCM wouldn't know which is #1 at TDC so wouldn't start spark

Picture here: https://www.fixmyoldride.com/images/...aft-pulley.jpg

You can see the missing tooth at about 9:00 lined up with crank keyway(#1 TDC), its labelled Reluctor ring, same as tone ring

PCM would show RPMs as crank starts to turn but without an IDed #1 TDC it would not continue, which is what you described, RPMs stop after 3 seconds

The tach on the dash uses spark pulses, so wouldn't show cranking RPMs unless there were spark pulses

 

Visual inspection of the tone ring showed no missing teeth, other than the one open spot. It was heavily rusted, so I cleaned it with soft wire brush.

Strobe test on the coil pack wire harness was hard to determine. Tested all three ground wires separately along with the one red wire. Results were the same each time. With key on the light would stay solid ON. While cranking the light would flicker dimmer, but never seemed to go off completely. I also noticed when ON the light wasn’t as bright as when I tested it direct to the battery terminal. On one of the test, I did see the bulb really flash bright one time as I was turning off the key from cranking. Almost like a backfire would do. Only did it that one time.

 

I’ve had three different mechanics look at this truck now, and all agree that according to the test results, the engine should be firing. They suggest that it could be related to the factory anti-theft system. It is a non-chip key system. The owners Manuel doesn’t have much detail about how it works, but it does say it’s job is to shut down the start up process. Does anybody know how the anti-theft system works on a 1995 Ford Ranger 4.0? What components are involved in the process? It sure seems like the only logical possibility left, that could be shutting down the ignition process while cranking. Thanks everybody for helping.

 

1995 is an Alarm system, so active, not like a PATS system, passive system

It only disabled Starter Motor, not spark or fuel
Your starter is working so not the alarm system

Did you ever do a compression test?
Even on 1 cylinder

Gasoline engine needs 3 things to start
1. spark, at the right time
2. fuel, with the right mix with air
3. compression, above 120psi, 155-165psi is expected on a 4.0l OHV

Maybe crank or cam gear sheared woodruff key and valve timing is off, 4.0l OHV is a non-interference engine, so valves can never hit pistons no matter how far off timing gets

 

Never did a compression test, but I replaced the cam synchronizer. Had the upper plenum, lower intake and both valve covers off. Used a wrench to rotate the engine to TDC on#1 cylinder. Saw movement in the valves and felt the #1piston movement. I’ll check compression just to verify.