1986 Ranger, automatic trans with the 2.9L. My friend bought this for his daughters first vehicle and wants everything correct and reliable. Brought to me with no brakes, new FPR, ignition module, spark plugs, coolant temp sensor, map sensor, idle air motor, new rear fuel pump, new front fuel tank and fuel pump. Truck would start and run rough. It would not get over 30 mph missing badly. Repaired the brakes and started on the running issue.
Fuel pressure is within spec. 40psi I think it was. Checking the spark plugs they were black, spark was very weak. Replaced ignition coil and connector. Spark is bright and strong now but no change in running. Checking ignition timing,, the signal for the timing light is cutting out with the engine, So i check the
signal to the ignition coil. It is also cutting out, causing the miss. Ignition module connector looks ok. Pins look good. Ignition module looks new so I replace the distributor which comes with a new module also. No change. Same issue when setting the timing. Then the fuel tank switching valve started leaking.
Replaced that with a factory valve also the fuel filter on the frame. It probably had never been changed. Fuel was very stale. Drained the tanks, Removed the fuel rail and cleaned the rail and replaced the injectors. Added fresh fuel to both tanks. Saw the oxygen sensor was rusted bad and barely connected.
Replaced with a new O2 sensor. No change in running. Fuel is good with no leaks now. Spark plugs have all been changed along with the wires because some of the wires came apart. I have an 89 ranger also I have swapped the computer with no change. The signal to the coil from the module is cutting out but I cannot figure out where or why. I have checked continuity on the wires from the EMC to the module connector with no shorts or opens. I have also checked several grounds and the fuseable link on the driver fender. I am really missing something if anyone could help I sure would appreciate it and thanks in advance.

 

Welcome to the forum

Very good testing and description of past changes

No, you have covered pretty much all the territory for spark
There is a SPOUT Connector that connects Computer to TFI(spark) module, its the "Vacuum Advance" for electronic ignitions
Unplug it
That will take the Computer completely out of the picture from the spark system
If cold, the engine won't want to idle so best to test with SPOUT unplugged after engine have been warmed up for a few minutes
Timing without SPOUT connected should be 10-12deg BTDC

The coil test is what is interesting, i.e. "the signal for the timing light is cutting out with the engine, So i check the
signal to the ignition coil. It is also cutting out, causing the miss"

If the coil's 12volt wire still has the condenser(AM radio noise suppressor) unhook it, longshot
Also test Alternator's B+ terminal with engine running and the Volt meter set to AC VOLTS, "AC Ripple test"
0.5vAC is tolerable but high, expected is under 0.4vAC
If a diode in an alternator leaks/fails it can cause all sorts of issues in a computer/electronic based engine system, AC is bad in a DC system, lol
OR
Just disconnect alternator and run off battery power when testing spark system

Up thru 1992 the 2.9l computer uses Batch Fire injection, it opens 3 injectors at the same time, and alternates the 3 on each RPM, like odd and even, 1, 3, 5 open, then 2, 4, 6 open, repeat
All injectors get 12volts with key on
Computer has 2 ground wires for injector control, one connected to 3 injectors, that it alternates each 1 full rotation of crank, 1/2 turn of distributor/Cam
If you still have the fuel pressure gauge re-install it
Turn on the key, engine OFF
Should see 10-30psi but holding steady
If its dropping then could be an injector is leaking a bit

There is a "Mode/Routine" in ALL fuel injected computers call "Clear Flooded Engine"
Its simple to use it
Key on
Press gas pedal down to the floor and hold it down all the way
Try to start engine
If should not start/fire at all, fuel injectors are shut off

They way it works relies on the TPS(throttle position sensor) working as it should
TPS gets 5volts from computer(most sensors share this 5volts)
When throttle is closed it sends back under 1volt, 0.69 to 0.99v is spec
When throttle is Wide Open(WOT) it sends back 4.5-4.7volts

With key on
TPS at 4.5v+
And 0 RPMs
Computer will go to "Clear Flooded Engine" mode and no longer ground injectors until TPS voltage is under 4.5v

Simple test to see if TPS is at WOT
Use a stick to hold down gas pedal
Go to engine and see if you can open the throttle more, if so you have a stretch throttle cable but easy fix
Google: Ranger throttle cable mod

If you do the "Clear Flooded Engine" test and engine does not start/fire then injectors and computer wires are OK
If engine fires/starts then check throttle cable
If its OK and you are getting WOT
Then disable spark, pull coils spark wire
Repeat "Clear Flooded Engine" test and crank it a few times
Pull out the spark plugs and check the tips for fuel, they should all be dry except for the one with leaking injector

 

The SPOUT I removed while setting the timing after distributor replacement. All of that looks fine. Truck only has 68000 miles on it so most everything looks almost new. The alternator issue I am familiar with on fords so we did test that before to find that the alternator was not charging at all. The alternator was replaced and checked for AC voltage afterwards. It does have a condenser on the coil circuit. No change with it disconnected. Fuel pressure goes to 30psi and holds steady after the key off. I'm really not leaning on anything mechanical inside because of the mileage. it runs like I'm switching the ignition key off and on randomly and I can see symptoms in the ignition circuit cutting out at the coil.

 

Now the original distributor had a grey module on it that had just been replaced when the truck arrived. When I replaced the distributor, the new one came with a black one. (zone) That is the only one (zone) offers beside the grey Motorcraft one. Should I change to the grey one. The engine is running exactly the same it was with the other distributor and module that were on it. This seems to be my next step...

 

Yes, for sure change to Grey Module, good read here on two different TFI modules: file:///C:/Users/Ron/Downloads/Ford%20TFI%20modules%20-%20Gray%20or%20Black.pdf

Rangers only ever used the Grey Modules up thru 1992