fustrated

[chief]

My 94 ranger 4.0 quit while driving like trhe key shut off i drug it to a friends shop where without riagnosing changed the coil pak for a nother used one as there was no spark this did not help still no start so i put the old one back and it started ran normal i put the scanner on it and erased any codes and shut off the truck now weont start again and my innova 3120 koeo test says vehicle not responding. any ideas before i start componet testing ?
oh ya it had fuel pressure at the shrader valve now i dont perplexing

 

[RonD]

Welcome to TRS

"i put the scanner on it and erased any codes......."
So while engine was running the scanner would connect to computer?
But not after you shut it off?

And you have used this scanner before on this vehicle?
Ford's OBD1 is often hit and miss with most OBD1 scanners, Ford didn't follow OBD1 protocols exactly

In the engine fuse box there is a 30amp EEC(PCM) fuse(#4) and an EEC(PCM) Relay.
When you turn on the key this relay will close and that 30amp fuse will power the computer(EEC/PCM), the injectors, and the Spark system.
So if this fuse blew or the relay failed the computer would have no power nor would spark, and engine would of course die and not start.
So you couldn't connect with scanner and would have no spark when cranking
Check fuse and also check that fuse has 12v power, could be wiring to the fuse holder
Make sure EEC relay is closing when key is turned on
Check for 12volts at any fuel injector or on the coil pack's red wire when key is on.
That 12v comes from EEC fuse via EEC relay


Spark system
1994 4.0l used an ICM(ignition control module), called an EDIS-6 for spark
It will be located on the radiator support, on my 1994 4.0l it is on the drivers side but on the FRONT side of rad support, have to look from underneath bumper to see it.

The spark system has 3 parts
CKP(crank position) sensor
EDIS-6 module
Coil Pack

CKP sensor is located next to the crank pulley, it reads a tone wheel behind the pulley, looks like gear teeth.
As the crank turns the CKP sensor sends a pulse that times the spark, it is "the points" for a distributorless system, so CKP failure means no start, but these rarely fail, not never, rarely
The wiring how ever is subject to damage, it runs up around water pump and thermostat housing and into engine wiring harness on lower intake, check it.
This wire runs to the EDIS-6 module

EDIS wiring here: http://www.dainst.com/info/edis/edis.html

You can test CKP signal using a volt meter set for AC volts, yes AC, when crank is turning with starter motor you should see 0.5 to 1vAC

EDIS-6 is connected to coil pack, EDIS times the spark using CKP signal
So this system is autonomous, it doesn't need computer to start spark
EDIS does send spark timing to computer, so computer can time fuel injectors
Computer also sends EDIS "suggested" changes for spark timing, computer has data from driver, like throttle position, so when driver presses down on the gas pedal computer will suggest spark should be advanced.

CKP sensor-----------EDIS module--------------Coil pack-------spark plugs
That's the spark system

EDIS-6 modules rarely fail, they are often damaged in front end collisions, so if truck has had front end repair, module could have been damaged, and has now failed.