1985 Ranger No Spark/No Ground to ICM?


OnePunchRabbit

New member
Joined
Apr 2, 2019
Messages
3
Reaction score
0
Points
1
Location
Texas
Vehicle Year
1985
Make / Model
Ford Ranger
Transmission
Manual
Hello!


To start off I'd like to say what a wonderful and helpful forum this is! So, I recently bought a 1985 ford ranger 2.3L manual as my first "real" project car, owner was upfront about the no start and told me he already threw a bunch of parts at it.


After messing with the truck for a few days, I narrowed down the no start to no spark at the ignition coil. I followed this article in diagnosing both the coil and ICM:


2

And the ground on the connector to the ICM only reads about 7.72v with the key in the ignition and in the on position. According to the article it should read about 10-12v. The next tests in that article failed.


Because of the article I believe there is a open circuit somewhere and I have no idea how to find it.


Now, the truck had a bunch of extra homerigged wiring put in for an after market head unit and speakers so I believe it could be because of that.


My question is, am I right with diagnosis or completely wrong? How would I go about finding the root of the issue? I do not believe its mechanical since the coil and module seem to be new (at least that's what the guy said)


I am not a master mechanic by any means and this is my first experience dabbling with electrical issues so any suggestions and advice are extremely appreciated!
 


Rock Auto 5% Discount Code: 173A8B749AB83C Expires: January 1, 2020

adsm08

Senior Master Grease Monkey
Supporting Member
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
32,163
Reaction score
1,465
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
I think your cause may be close, but your reason for it is out in left field. Nothing done near the radio should have any effect on the ignition module.

Low voltage is often caused by a bad wire, something chaffed or corroded, or some other cause of high resistance.

I would start by testing the key on voltage at the ignition switch and if that is the same as the battery, then test the resistance from the switch out to the ignition module connector.

You do seem to be on the right track.
 

OnePunchRabbit

New member
Joined
Apr 2, 2019
Messages
3
Reaction score
0
Points
1
Location
Texas
Vehicle Year
1985
Make / Model
Ford Ranger
Transmission
Manual
I think your cause may be close, but your reason for it is out in left field. Nothing done near the radio should have any effect on the ignition module.

Low voltage is often caused by a bad wire, something chaffed or corroded, or some other cause of high resistance.

I would start by testing the key on voltage at the ignition switch and if that is the same as the battery, then test the resistance from the switch out to the ignition module connector.

You do seem to be on the right track.
Hello!

Thank for your response! I didn't think about the ignition switch! I'll make sure to test that. The thing is according to that article the wire that provides power is getting battery voltage its just the ground thats not keeping up.

I believe when I tested it with the ignition completely off it registered battery voltage. What would cause the ground to register less if the key is in the on position or is that normal?

Some of the other grounds in the area are fine as I tested them with a test light.

Thank you for any more advice in advance!
 

adsm08

Senior Master Grease Monkey
Supporting Member
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
32,163
Reaction score
1,465
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
Grounds should never have any voltage. Voltage should come from the battery, go through a switch of some sort, and drop across the load, and show no voltage on the ground side of the circuit.

Now if you have a properly operating circuit, disconnect the ground wire from ground, and turn the circuit on you can see some voltage because the open you created in the ground side is now a bigger load than the device you are trying to operate, so not all the voltage will drop if you do that.
 

OnePunchRabbit

New member
Joined
Apr 2, 2019
Messages
3
Reaction score
0
Points
1
Location
Texas
Vehicle Year
1985
Make / Model
Ford Ranger
Transmission
Manual
Sorry for all these noob questions!

From what I understood from your explanation the fact that the ground on the ICM connector is showing around 7v when the ignition is in the on position indicates that there is an open circuit somewhere and it cant properly drop the load?

In your opinion, where should I start looking for this open circuit? Start from the ignition switch?
 

adsm08

Senior Master Grease Monkey
Supporting Member
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
32,163
Reaction score
1,465
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
With the key off, battery positive cable unhooked, test continuity to the battery ground from the ICM.

If the resistance is less than 5 ohms use some jumper leads and a paper clip to hook up a headlight bulb to the battery and try to ground it with that wire.

Resistance tests are not the end all of if a wire is good or not. It can ohm out OK, but not be able to carry a load well. The light bulb test will tell you if it is not carrying the amperage it needs to.
 

RagingBronco

New member
Joined
May 31, 2019
Messages
8
Reaction score
1
Points
3
Location
Colorado
Vehicle Year
1984
Make / Model
Ford Bronco 2
Transmission
Manual
@OnePunchRabbit Did you ever find out why the ground only read 7.72V at the ICM? I'm having similar problems with a bronco that I'm working on and it results in no spark.
 


Top