Sport Jet 90 and 120 Ignition Tests

 

Follow the tests in the following order to diagnose your ignition. If you have lost all spark, your most likely culprit is the stator or the switchbox. If you have intermittent spark it could be anything. Either way, follow these tests in order and it they will tell you what the normal results should be.

 

Some technical terms

 

DVA stands for digital voltage adapter. It tells you the peak volts on a AC circuit. You don’t really need a DVA meter, you can just put a normal Multimeter on AC volts and multiply the readings by 1.41

 

Rev limiter is a 1 inch by 1 inch box with 4 wires that can be found in two places. Older models have it under the starter solenoid, newer models have it by the switchbox.

 

Switchbox is a 2 inch by 4 inch box with about 12-15 wires coming from it. One note on the switchbox is that when you use the red stator adapter, you no longer use the red wire coming from the switchbox. I have heard that CDI/Rapair stators go back to the black stator style, that is, they don’t use the red stator adapter and will use the red wire from the switchbox.

 

Red stator adaptor is a ¾ inch by 3 inch long thing that is used when the engine is upgraded from a black stator to a red stator. Most engines have already done this cause the black stators did last more than a couple of runs.

 

Keyswitch test

Red Multimeter lead to black/yellow wire from switchbox (wire disconnected from switchbox)

Black Multimeter lead to ground

Turn key in all positions, there should be zero voltage in all positions

There should be zero ohms in off position and infinite ohms in start or run positions

 

Rev limiter test

Disconnect black/yellow wire from rev limiter

If engine runs fine, the rev limiter is bad (these are common things to go bad)

 

Stator ohms test –         600-700 ohms Green/white to white/green, infinite to ground

0.6-1.1 ohms yellow to yellow, infinite to ground (my stator has zero ohms and charges the battery fine, but my meter may not be that accurate)

 

Red Stator output Test – 180 DVA (or my stator puts out 120 AC volts)

Between green/white and white/green wires while cranking – too low and your stator is junk

 

Trigger Resistance Test for 90 hp 3 cylinders - 1100-1400 ohms

Between white/black wire and the three other trigger wires – I had one wire show infinite ohms and had a miss on that cylinder

 

Trigger Resistance Test for 120 hp 4 cylinders - 700-1000 ohms

Between violet and white wires and again between brown and white/black

 

Red Stator Adapter Test - 65 AC volts or 110 DC volts

Between blue wire and ground while cranking (personal test, not from any manual)

 

Ignition Coil Resistance Test - 0.02-0.04 ohms between positive and negative terminals

800-1100 ohms between spark plug lead (with spark plug wire removed) and negative terminal

 

The below tests are not necessary in my opinion because if all the above checks out, then the switchbox is bad, the spark plug wires are bad, or there are shorts in the wiring. Check all wires for shorts.

 

Switchbox Stop Circuit Test – 200-360 DVA volts

Red DVA lead to black/yellow wire from switchbox

Black DVA lead to ground

Crank engine

 

Switchbox Output Voltage Test – 150-250 DVA volts (180-280 DVA engine running)

Red DVA lead on #1 cylinder coil positive terminal

Black DVA lead on #1 cylinder coil negative terminal

Crank engine

Repeat for the other coils

 

Switchbox Bias Test – 2-10 DC volts (10-30 DC volts engine running)

Red Multimeter lead to ground

Black Multimeter lead to white/black wire on switchbox

Crank engine