Bad coil?

[moosemeadows]

93 explorer 4.0 in an 87 bronco ll Have 12v to coil on red/grn have 12v on other 3 leads with test lite hooked to positive grd No spark at plugs or out of coil Tells me it's a bad coil What do the rest of you think Thanks in advance for your input. Really would like to get this this out of my shop

 

[moosemeadows]

Up date Just check resistance 0.0 on primary 13.5 on secondary I'm still going for a coil in the am unless somebody shows me different

 

[jeremysdad]

0 ohms primary side would be shorted coil.

Was it running when pulled?

 

[moosemeadows]

Not sure bought it as an undone project of someone else who didn't want to mess with it any more. I found and learned alot getting to this point and I hope that this will be my last piece to make it run. Wiring was messed up by not being done correctly fuel lines weren't hooked up correctly and just alot of other small stuff but all put together makes one big puzzle So you think the coil's the issue? Could it be anything else? Thanks for your help.

 

[RonD]

You need to test Primary coils OHMs using meter's lowest OHM setting because it is just a short coil of wire inside, so on higher OHM setting it would/should show 0 OHMs.
At lowest OHM setting you would see .6 to 1.4 OHMs

And there are 3 separate coils in the coil pack, all 3 "could" be bad, but...............

1993 4.0l will use an EDIS-6 module to run the coil pack, it was located on the rad support of explorers and rangers, and is often left behind when parts are pulled.

Picture of the module here: http://www.r3vlimited.com/board/showthread.php?t=124704

Crank sensor runs to EDIS and the 3 coil Grounding wires, and then a few wires from EDIS to computer

 

[moosemeadows]

Ron D again thank you for your insight When coil was tested meter was set to 20 scale as it was as low as I had for primary and 20K for secondary. Have the EDIS module and it checks out for getting juice to and from. Checked crank sensor for output and it just moved the meter when tested so I think that is good as well. Thank you again so off to another day of playing in garage.

 

[RonD]

EDIS Modules are self contained, meaning if they get Crank sensor pulses then they will run the coil pack, generate spark without computer input.

The computer hook up is to give computer fuel injector timing and RPM, computer sends the EDIS suggestions on spark advance and retard based on driver input(gas pedal, TPS)

One thing that can happen is mis-wiring in the START circuit, i.e. you have 12volts at EDIS and coil in RUN, but when key is turned to START voltage is cut.
So you would have no spark when cranking but all voltages are correct in RUN

The power for both comes from the EEC(PCM) Relay in a 1993, it also powers EEC(computer) and Fuel injectors.
I would test for power at coil connector while cranking, it will drop to 10volts but not to 0volts.

I think the 1987 powered the ignition via the NSS or Clutch switch when key was in START position, power from RUN position was cut at that time

 

[moosemeadows]

Will go look into that now as well. Has gotta be something simple that I've overlooked. Did you mean 10 v cranking or 10 ohms? Will check back later Thank you again for your advice.

 

[Andy D]

Will go look into that now as well. Has gotta be something simple that I've overlooked. Did you mean 10 v cranking or 10 ohms? Will check back later Thank you again for your advice.

10 Volts
whilst cranking over with the starter. Good luck

 

[moosemeadows]

I ran into this way back when I was building my 55 Chevy with a HEI dist using stock ignition switch. Then I used a jumper on the switch to get voltage to the coil to start. So if I'm reading and more importantly understanding correctly I need to get tied into my NSS for all of this to work. HUH?

 

[RonD]

Well yes and no.

The '93 will just have the Starter Motors "S" wiring running thru the NSS(automatic)
So trans must be in Park or Neutral for starter motor to activate.
"S" wire is the Red/blue wire that would go to the smaller "S" post on fender mounted starter relay(solenoid), starter relay was combined with starter motor in later years, so "S" wire would go there.
But in either setup it would go thru NSS or Clutch switch first

If you had voltage at the Coil when cranking then all is well with power.
Yes, 10volts because starter motor pulls voltage down when its running.

 

[moosemeadows]

Ron will check in am on cranking voltage at coil Wife was gone garage shopping today and didn't get back till late. I'll grab her am to go test before she gets out of here again. If that doesn't work I'm going to start all over from the start to make sure I didn't make any mistakes on initial wiring. Got me stumped because it turns over just fine with the key and clutch engaged Haven't got to do the dash stuff yet but I think that will be pretty straight forward or I hope it is. Well there's always another day in the shop to look forward to.

 

[moosemeadows]

update Sat morning Had wife come help got 9.7v while cranking Should fire with that I guess.

 

[Andy D]

Not familiar with the 2.8. Is there any way to spray carb cleaner or starting fluid into the throttle body? A pump sprayer with a little gas in it ? If the engine fires once , it is a fuel trouble.

 

[moosemeadows]

Andy it's had a transplant Got some new life from a 4.0 out of a 93 explorer Hence from which all the issues arise. I've tried carb cleaner thru the plenum no bark but plugs were wet.Everything leads to a spark issue in my mind Still no spark to plugs. Gotta be something stupid I missed