2.3L ('83-'97) 1988 no spark

[Chris M.]

New TFI and coil installed. Checked KOEO at TFI plug is 12V at RUN but only 1.5V at COIL. Next step???

 

[RonD]

Should be a red/light green stripe wire at TFI run and Coil +, it is just a spliced wire from ignition switch that runs to several systems with key ON(run)

I would first just put a jumper wire from battery positive to Coil + and see if engine starts and runs, if so then you unwrap wiring harness to find the Splice and repair it
Or run a new wire from red/green at TFI to Coil +

Diagram of the wiring here: https://www.therangerstation.com/tech_library/EDiagrams/files/Diagrams_StartIgnition83to88_2_3.JPG

Wire in question is R/LG, red/light green stripe

 

[Chris M.]

Sorry for any misunderstanding, the 1.5V is at the TFI plug for coil -. At the coil itself I read 12V coil + and 1.5V coil -

 

[RonD]

If the coil has 12v on + then there should also be 12v on - if TFI module is unplugged

An ignition "coil" is just that, a coil of wire, so 12v in = 12v out

If you only see 1.5v on the dark green/yellow wire in the TFI connector(unplugged) then that wire is bad

If TFI connector is plugged in and key is on then yes, that wire would be low voltage as its a GROUND, this powers up the Coil so when its unGROUNDED it will spark

If you have a test light hooked to battery positive and Coil - then light should pulse on and off while cranking, hard to see that on a digital volt meter, old analog meters would show the pulse

Ignition coils have the Primary coil the 12v part, and then the Secondary coil the spark part
When Primary has 12v and ground it creates a magnetic field around the Secondary coil
When power is cut to Primary(ungrounded) the magnetic field collapses and the Secondary releases its Spark voltage

Points grounded and ungrounded the Coil in older distributors to get spark
Electronic ignitions use a sensor and transistor to ground and unground the coil
A hall effect sensor inside the distributor tells TFI when to ground and unground the dark green/yellow wire(coil -) as the distrubutor shaft spins