I have a 1989 2.9l ranger that I swapped a 1993 explorer 4.0l into a year ago. it ran perfect for a year as I was building the suspension. got it driving and went for a 5 mile drive. parked it for a week, went out the next weekend and it would crank but not start. found no spark. did a full tune up with no success. tried a spar ckp I had laying around and it fired right up. started it every night for the next week to move it to the garage to finish some small stuff. parked tit Friday night. went out Saturday night and it would not start again. have no fuel, and no spark. swapped relays around and got fuel to come back, but still missing spark. warrantied ckp out and installed, no spark. coil has 12v on red wire, when I plug the coil connector in, all other wires have power also. are they supposed to switch to ground from the ckp or should they switch from ground to power? im about ready to sell the truck and cut my losses.

 

Welcome to the forum

1993 Explorer should be using the EEC-IV 60-wire PCM(computer), which has no spark control, that came in 1995 EEC-V 104-wire PCM

So the 1990-1994 4.0l OHV used an EDIS-6 spark system, it had 3 parts
Crank sensor
EDIS module
Coil pack

The EDIS system is self contained, doesn't use the computer for startup spark control, it was a popular system for hotrodders because of this

EDIS module was also connected to PCM to send it timing pulses for fuel injectors, and PCM would send back spark advance suggestions, i.e. like vacuum advance on old distributors, the EDIS module just had RPM spark timing advance/retard, it needs driver input to be responsive, and PCM has that info

When you did the swap you had to bring over the EDIS-6 module with wiring harness so I would start there, the wiring
The modules were usually mounted to the Rad support, they get hot so need to stay cool

Info here on the EDIS and wiring: Ford EDIS technical information

Since you lost spark and fuel injection the EDIS system is the only common denominator, PCM starts injectors ONLY when it sees the timing pulse coming from EDIS system, i.e. crank sensor and module

 

i swapped the headlight harness, dash, and engine harness from donor vehicle. everything but the wiring for the rear half of the truck is all explorer

 

So track down the EDIS module, it was part of the engine harness
Crank sensor and coil pack both connect to the EDIS module

EDIS-6 picture here: http://www.mkosonen.com/edis6module.jpg

Picture of all 3 parts of system here: https://www.bimmerforums.com/forum/s...-and-VR-sensor

I would do a 50/50 test just to confirm your symptoms
Spray fuel into the intake and try to start engine
If it starts and dies then its a fuel only issue, spark is working
If it doesn't start then its a spark issue
50/50 instant results

 

yes I have all of the system installed on the truck. ive had it running and driving after the swap but have now lost spark. I have done a new ckp, coil, plugs, and wires. still no spark. gonna try a icm next.

 

The EDIS modules rarely had any problems, almost always a wiring issue

If vehicle had a front end collisions and physically broke the module mounted on rad support is about the only time they needed to be replaced, lol.

 

other than visual inspection, what test can I do to narrow down my problem? I have power at the coil via red wire.

 

Same red wire source(EEC Relay) powers EDIS module, also a red wire on pin 8

Unhook EDIS 12pin connector and have a look at the inside, corrosion or frayed wires at connector

 

no corrosion in module and found no issues with connector. have small amount of dielectric grease in terminals.

 

You can test crank sensor at the EDIS-6 connector

Crank sensor is a VR(variable reluctance) sensor, which means it generates its own AC Voltage
Hook up a Volt meter to pins 5 and 6 on the connector
Set volt meter to AC Volts
Crank the engine over, should see above .5 to 1 volt AC, depends on crank speed, faster speed = higher volts

If erratic or no volts then trace the wires back to crank sensor

Key doesn't have to be on if using a remote start unit on starter motor, crank sensor makes it own AC Volts

 

I'll do this tomorrow after work and replay back with results