Dwell test port for FV duty cycle Question

[scmguru]

I'm trying to verify the duty cycle of a frequency valve on my 86 930 and when I connect the dwell meter to the test port, I am getting an incorrect value (10 deg).

The dwell meter has 2 leads (green and black), I am connecting the green to the top pin on the test port and the black to an engine ground.

Should both leads be connected to the test port?

The meter is analog FWIW.

Thanks!

Mike

[CMXI-SC]

Don't have the answer but would also like to know

[psalt]

Mike,

Look at the wiring diagram, the signal wire in the test plug usually is green with a white stripe. This should be connected to the green dwell meter wire. The brown wire in the test plug is ground but it usually is easier to use the engine. The dwell reading on the 4 cylinder scale, divided by 90%, equals the duty cycle. You should see the default setting until the engine warms up, then a rhythmically oscillating needle once it goes closed loop.

[scmguru]

Thanks folks. I tried connecting to the green/white and using the engine as ground and Im getting an incorrect value which is fixed at 15 degrees or so.

I know the FV is working and w/ O2 sens disconneted should be at 50%.. so I don't know if the analog meter is bad or there is a problem w/ the FV duty cycle.

Will take a picture later and post it.