Drop down test

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,250
I've been searching through the "archive" of previous posts regarding a drop down test but can't really find my answer.

With the engine running pull the plug wire of the Spark plug to test a change or not.
It is advised to have the spark plug grounded when checking the ignition-system, so it will not damage the (Prestolite) switch-boxes.

Here's my question;
In order to do the drop down test, do I unplug the wire to the coil?
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,926
No.
The cyl. drop test.
Just unplug the wire at the plug as it runs.
Use insulated pliers and leather gloves and stand on a piece of wood.
Even then it can get ya!!
If the cylinders firing the hot is looking for someplace to go and YOU'R the easiest route.
shopping

shopping
 

Nordin

Commander
Joined
Jun 12, 2010
Messages
2,436
Your are thinking in the right way, but when doing a drop down test you just pull the HT wire for maybe 1-2 seconds.

Doing a compression test with not grounding the plugs you usually turn the engine over for 8-10 seconds and that is more dangerous for the CDI boxes.
 

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,250
Your are thinking in the right way, but when doing a drop down test you just pull the HT wire for maybe 1-2 seconds.

Doing a compression test with not grounding the plugs you usually turn the engine over for 8-10 seconds and that is more dangerous for the CDI boxes.

THANKS:whoo:Nordin
 

Redbarron%%

Chief Petty Officer
Joined
Dec 7, 2017
Messages
479
The ungrounded plugs might not damage the box, but the high voltage with no drain from the plugs might easily damage the coils and that might damage the box.
But... I have limited experience with these engines.
You could unplug the trigger wire and perhaps get to it easier and with less risk?
Of course the problem might be the breakdown of the trigger circuit as well.
I had this problem. The engine would run OK at low rpm on the hose, but not pull underload in the water.
A new trigger coil took care of my problems. but at the same time I complicated my system and thinking bu converting to the CDM modules and eliminating the CDI box.
That set in play the questions about the trigger bias circuits.
 

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,250
No.
The cyl. drop test.
Just unplug the wire at the plug as it runs.
Use insulated pliers and leather gloves and stand on a piece of wood.
Even then it can get ya!!
If the cylinders firing the hot is looking for someplace to go and YOU'R the easiest route.
shopping

shopping

I went & bought the tool.

I wrapped additional tape around the handles & fork as far as possible to minimize/eliminate current-jumps.
have not tried it yet
 
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