Autophysn

Hello guys and gals, I am new here, tried a search but could not find anything directly relating to this. If it is a killed topic, please forgive me and post a link to a thread that could help.

I have a 1985 carbureted 22r Xtra Cab, My Father in law drives it every day.
Looks like the Alternator went out, but the local "mechanics" checked it out and before I knew it, they had the starter by passed, blew the 60A main fuse, and removed the ignition control module.

Long story short, I am a mechanic, feel free to use the big words and tech talk.
I am just looking for the proper procedure in diagnosing a ignition control module and pick up coil for this truck. If it were not such a costly item, I would just replace it, but you know all too well, these things are not cheap. My coil is getting 7.5 ohms of resistance from both terminals to the plug wire lead, and I have no spark at this time.

I will most likely be replacing the distributor with a rebuilt one (advance plate is frozen ) so I will get a new pick up coil with that. However I am not sure how to check if the ICM is good or not.

Any help would be greatly appreciated, Thank You!

jimmi22r

Hey Auto,

Did you ever receive an answer on this topic? I'm tring to figure out the same thing.

Autophysn

Yes, I did. But not from here. I found it in the shop manual. I forget the procedure, but it involved using a ohm meter and a AA battery.
It failed the test, so I coughed up the $400 for the part. Fired right up after that and runs very well now.
Not sure where you are, but here in SoCal, it was much cheaper at Kreagan or should I say O'Reilly vs AutoZone. I think AZ wanted around $500, and O'Reilly it was like $380.
Try googling the shop manuaI, or I bet someone here has a link. I was fortunate to have a hard copy. I don't have access to it anymore, or I would have posted it.

It was pretty easy. Just hard on the pocket....

lauriepaul

You was testing for IGF signal it discharges the secondary windings in the coil to produce a spark. And also tells the computer its sparking so it keeps firing the fuel injectors and stay running. You can do this in 2 ways .first put the hi tension wire coming out of the coil "next" to metal then in your dizzy is your pick up coil .Now when to tooth in the dizzy passes that pick up coil you,ll get a spark with the ignition in the on position not start.

This tests IGF and pickup coil in dizzy:

1) Get a small screwdriver wrap the metal tip and up with one layer of electrical tape just so it does,nt short anything out.Now with ignition on (Not started ) You hover that screwdriver tip over that little coil/signal generator in the dizzy(Inducing a voltage in that little coil) you should get a spark out the coil wire when its close to metal ground(Valve cover).

2) Another way you can do this is get you a 1.5v battery unplug that little coil in the Dizzy.Now that wire you just unplugged the side going to igniter/ignition control module you have 2 wires red and white you need to put that battery across those two wires just for a second with the ignition on (Not start) you should get a spark .
If ethier of these 2 methods dont produce a spark then :

1)Your your little pickup coil in dizzy should ohm around 200 and when you pass a screwdriver over it while you ohm it the ohms will jump round that means its good.(if out of spec its bad)
The airgap between your dizzy pickup and the teeth wheel should be 0.2mm

2)Your connections are bad back probe them

3)Your Ignitor ground is bad check the big bracket it sits on. The bolts that hold it to the body get rusted and you lose ground .You can put your own ground wire from the igniter body screw to the engine

4)You can test for IGF put a volt meter between -minus on the coil and other wire on the body of the Ignition module. With ignition on you get 12-13v battery voltage crank the engine and it should drop do this with the dizzy pick up coil plugged in and the 3 pin NE,IGF,IGT un plugged !



For signal NE and IGT
I think the NE signal tells the ECU to send the IGT signal to the igniter By grounding the voltage from The NE pin at the ECU(12-13v) through the ignitor when cranking. So in theory if you was to un ground the igniter and remove the coil input and keep the signal generator in the dizzy attached and your NE,IGT,IGF plugged in when you connect a voltmeter between the igniter body and ground You should see the voltage at the NE pin on the ECU go through your meter when you crank it !( I COULD BE WRONG ON THIS HOPEFULLY SOMEONE WILL CORRECT ME )

When cranking the the NE signal is used to tell the ECU Ignition timing using the distance of the teeth in the Dizzy passing over the signal generator once this is confirmed the ECU caculates this with other sensors signals.And sends The IGT signal(Ignition timing )To the igniter/Ignition control module.Once your engine starts the Ne signal is used to monitor the engine RPM/speed of the teeth in the passing the pick up coil.When Iginter recieves the IGT signal it causes the secondary coil to be grounded and also send the IGF( I got fire) to the ECM .If the ECM does,nt recieve the IGF signal it will cut the power to the Fuel injectors and fuel pump.
(IF I AM WRONG ABOUT THIS YOU CAN CORRECT ME )
Hope this helps you all !