"84 75HP L4 Ignition question

[goat roper]

I started out with no fire except cylinder #4. Using the specs, an ohm meter and a DVI adapter, I found the stator, trigger and coils all tested within specs. Next, I moved the primary side wires from coil #4 to each of the other three coils, one at a time, and got fire in each one, firing the plug for that cylinder. Unable to find a way to test the switch box, I have to conclude that through trial and error, the switch box is faulty. Do you agree or is my thinking flawed? Also, are there any opinions as to the reliability of the Sierra after market switch box?

 

[racerone]

Charge the battery.----Load test the battery.-----Take starter apart for inspection.-----No money spent for those steps.

 

[goat roper]

Charge the battery.----Load test the battery.-----Take starter apart for inspection.-----No money spent for those steps.

Thanks but there is a new, fully charged battery in use. I think a 4 cylinder with 145 lbs of compression on all 4 and the plugs installed is a pretty good load test for battery and starter. It cranks just fine. Thanks.

 

[racerone]

A new switch box fixes them 9 of 10 times.

 

[goat roper]

A new switch box fixes them 9 of 10 times.

I'm glad to hear that. It is the only thing left in the ignition circuit that hasn't been tested but the process of elimination pointed that direction. Thanks racerone!

 

[leachy]

I had a similar issue and that's how I checked it. Turned out to be the switch box.