Dwell issues

[Funracer]

After dozens of failed attempts to use a DMM with duty cycle setting to set my frequency vibrator to 45% I decided to try my very old 1980s Actron Dwell meter. It only has two wire green and black. I put green to green wire on test port and black to ground. Notice this meter has a six cylinder scale, its the very bottom one. Left new O2 sensor connected

Ran car for 20 minutes hooked it up this is what I got



No dizzying just solid needle. It would move a bit with mixture screw but it is not acting like it should from the many posts I have read about it.

Stuck in open loop? If so shouldn’t it read 65%

Am I using it properly?
Thanks

[john walker's workshop]

Fresh 9V battery?

[AndrewCologne]

There are many Dwell meters with analog Display out there not working properly when uising for CIS dutycycle measurement. I got one here with also just black and green connections, ... and doesen't work ... another Bosch one works. So it depends on the specific model.

BTW: here in this case you shoud a) read the 4 cylinder scale and b) when using the dwell meter then dutycycle = dwell * 100/90 ... as 100% dutycycle equals to 90 degree dwell.

[Funracer]

Originally Posted by john walker's workshop

Fresh 9V battery?

No place for a battery

[Funracer]

Originally Posted by AndrewCologne

BTW: here in this case you shoud a) read the 4 cylinder scale and b) % dutycycle equals to dwell * 0.9 as 100% dutycycle equals to 90 degree dwell.

Even though there is a six cylinder scale?

[Funracer]

Also tested my less than one one month old O2 sensor last night. DMM red probe inside female end of O2 connector and black to ground with O2 sensor hot and still in the catalytic converter. Looking for about .5VDC but it showed less than .1 VDC after 30 minutes engine running. I would like to pull the sensor and do the torch test but I am leaving town in the morning so it will have to wait.

I can hear the FV run when I lift the air plate with the key on, and I can also feel the O2 control relay click when ignition turns on. My DMM cost $45 from HD and has HZ% setting but I can not get it to show anything other than 70-80% Duty Cycle. Its possible my DMM nor my old Actron dwell meter are giving me the duty cycle.

I have a Gunson Gastester that works well and I set the CO last night to .6% CO. Car runs great but the Gunson is a bit of a pain to use. I am looking for an easier way to verify mixture moving forward. Measuring the FV will be the ticket but so far I have not been able to get the readings anywhere near 45%.

[AndrewCologne]

Originally Posted by Funracer

Even though there is a six cylinder scale?

Cause youre actually not measuring the ignition dwell but using the dwell Meter for measuring the frequency valves pulse width modulation, means dutycycle

[AndrewCologne]

Also tested my less than one one month old O2 sensor last night. DMM red probe inside female end of O2 connector and black to ground with O2 sensor hot and still in the catalytic converter. Looking for about .5VDC but it showed less than .1 VDC after 30 minutes engine running. I would like to pull the sensor and do the torch test but I am leaving town in the morning so it will have to wait.

That wont work. The remaining o2 in the exhaust flow needs to be the result of an AFR exactly set to stoich (14,7:1 or 14.4:1 at e5). If you pull the sensor Connection for measuring the ecu switches to a static 50% dutycycle mode. And as then theres no lambda controll running with a deconnected sensor youre 99,9% out of stoich. So: youll never read a 0.5v output with the sensor unplugged .

[AndrewCologne]

Why didnt you keep using your other thread? As by this your subject becomes splitted and its harder to follow.

[AndrewCologne]

Originally Posted by Funracer

No place for a battery

One thing ... that above is maybe the reason why such dwell meters won't give a proper duty cycle result, .... as you need a powered dwell meter. Via internal battery power or via given red/black wire 12v connection

[Funracer]

Originally Posted by AndrewCologne

Why didnt you keep using your other thread? As by this your subject becomes splitted and its harder to follow.

Because I was attempting to measure Duty Cycle with a DMM. This thread I switched
to a Dwell meter. Some people prefer this over DMM so I thought it might draw additional eyeballs.

[Funracer]

Originally Posted by AndrewCologne

One thing ... that above is maybe the reason why such dwell meters won't give a proper duty cycle result, .... as you need a powered dwell meter. Via internal battery power or via given red/black wire 12v connection

Ok thanks. May look for one.

[Funracer]

Originally Posted by AndrewCologne

That wont work. The remaining o2 in the exhaust flow needs to be the result of an AFR exactly set to stoich (14,7:1 or 14.4:1 at e5). If you pull the sensor Connection for measuring the ecu switches to a static 50% dutycycle mode. And as then theres no lambda controll running with a deconnected sensor youre 99,9% out of stoich. So: youll never read a 0.5v output with the sensor unplugged .

Ok next time I will leave it plugged. Not sure how to back pin this particular connector though.
Even if it is pulled from the coupling shouldn’t it still show .1to .9 volts? Mine showed .04 volts or thereabouts with car running for 30 minutes. Tried 2 diff DMM. Ordered another one last night and will install next week as I am out of town til Saturday. I will also be checking the sensor wire and maybe replacing the plug with spade terminals or something. My ceramic is mostly gone and the connection is very loose.

Thanks to all so far. I will get this figured eventually.

[AndrewCologne]

Even if it is pulled from the coupling shouldn’t it still show .1to .9 volts? Mine showed .

Read above, ... if the sensor is unplugged then the lambda "control" is switched off and the ECU runs in its home mode the frequency valve with a static value of 50%.
And as then the exhaust is not controlled and the AFR mixture therefore is not regulated anymore, you're 99,9% out of stoich, means not within 0.1 and 0.9v. IF you measure a value of 0.04v with a hot engine and sensor unplugged then your basic CO setting is simply too lean. But how much, you won't know as the narrowband sensor signal just tells you "too rich" or "Too lean"if out of bounds.

Ok next time I will leave it plugged. Not sure how to back pin this particular connector though.

Remove the passenger seat und watch the big wiring which leads to the big plug of the ECU ... if you verrrrry carefully cut a small slice into the outer black PVC jacket you can see beside the other coloured wires the green/white one from the test port. Just tap that signal and read the Dutycycle in the car in a more comfortable way, even while driving.

I will also be checking the sensor wire and maybe replacing the plug with spade terminals or something. My ceramic is mostly gone and the connection is very loose.

When replacing the Plug then switch to a more modern connection like a Super Seal based one, ... as mentioned in the other thread.
https://www.kabelschuhe-shop.de/AMP-Superseal-Set-2-Polig_1