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davlance01
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Joined: May 10, 2013
Posts: 224
Location: Ohio
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 Posted: Sun Jun 06, 2021 8:57 am Post subject: Re: Oscilloscope waveforms of fuel pump, hall sensor, injector, spar |
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| Abscate wrote: |
| Did you source and document the pressure sensor up thread or did I miss it? |
I didn't know there was a pressure sensor up thread to source and document.
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davlance01
Samba Member
Joined: May 10, 2013
Posts: 224
Location: Ohio
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| Posted: Tue Jun 15, 2021 8:11 am Post subject: Re: Oscilloscope waveforms of fuel pump, hall sensor, injector, spar |
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Idle stabilizer test...
-Back probe both green wires on the in and out side of the idle stabilizer. Purple is IN and Green is OUT.
-Start car and adjust idle above 940 rpm. (Make sure you mark and count the turns on the idle screw). The idle stabilizer does nothing above 940 rpm
waveform above 940 rpm
-Turn idle screw in slowing down the rpm below 940 and observe the two signals separate as the idle stabilizer is adjusting the timing to keep the engine running.
waveform between 500 and 600 rpm. (barely running)
-You can clearly see the 2 pulses moving away from each other at low idle. This shows the idle stabilizer is doing its job and I would say that its good.
The idle stabilizers job is to advance the timing so the rpms raise to 940 but by starving the engine of air by turning in the idle screw the idle stabilizer can't possibly raise the rpm but we can still observe the stabilizer working.
-If the 2 pulses do not move away from each other and stay aligned like what is shown in the first pic and the engine rpm is well below 940 then I would say the idle stabilizer is junk and needs replaced.
-Don't forget to reset your idle back to where it was before the test 
Hope this helps anyone diagnosing an idle stabilizer.
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Vanagon Nut
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Joined: February 08, 2008
Posts: 10371
Location: Sunshine Coast B.C.
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| Posted: Tue Jun 15, 2021 12:19 pm Post subject: Re: Oscilloscope waveforms of fuel pump, hall sensor, injector, spar |
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Glad I saw this thread.
If the distributor hall is suspected of causing a stall when RPM dips below idle spec, would the hall wave form reflect that fault just before the stall happens? If so, would one look for a missing square wave or ?
Thanks,
Neil.
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Abscate
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Joined: October 05, 2014
Posts: 22648
Location: NYC/Upstate/ROW
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| Posted: Tue Jun 15, 2021 2:30 pm Post subject: Re: Known good waveforms |
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| davlance01 wrote: |
purple spark line
green hall effect
cyan running compression with pulse sensor
825 rpm
4.2 degrees ATDC
84 vanagon with a stock 1.9
BTW: the timing light shows more than 60 degrees BTDC!!!!! |
Your compression pulse sensor
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davlance01
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Joined: May 10, 2013
Posts: 224
Location: Ohio
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| Posted: Tue Jun 15, 2021 3:24 pm Post subject: Re: Oscilloscope waveforms of fuel pump, hall sensor, injector, spar |
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Grabbing waves and interpreting waves are 2 different things.
With that being said I don't know what you have probed there but if it's the hall, idle stabilizer input and output you have some weird issue going on there. The input to the idle stabilizer should mirror the hall effect in the distributor exactly.
So in short set idle above 940 and all 3 signals should be the same time but a higher voltage on the output of the idle stabilizer.
You should only see the idle stabilizer output move and only below 940 rpm and from my wave captures it doesn't move all the much really.
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davlance01
Samba Member
Joined: May 10, 2013
Posts: 224
Location: Ohio
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| Posted: Tue Jun 15, 2021 3:39 pm Post subject: Re: Known good waveforms |
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| Abscate wrote: |
| davlance01 wrote: |
purple spark line
green hall effect
cyan running compression with pulse sensor
825 rpm
4.2 degrees ATDC
84 vanagon with a stock 1.9
BTW: the timing light shows more than 60 degrees BTDC!!!!! |
Your compression pulse sensor
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I 3d printed my sensor and adapter to pull the running compression because my ebay one sucked and you can't hook them directly to the engine cause it blows them to pieces.
You can purchase a transducer that will take it but again don't buy one of those cheap Chinese ones because they suck too.
My design uses vacuum to grab the pulses not direct pressure.
If there is any interest in them I can post the files on thingiverse.com or I can print you one out. You can leave mine hooked to a running engine with the harbor freight compression tester hose (with the valve taken out) about 5 minutes before the plastic gets hot enough to blow the sensor off. Then you just need to let it cool screw it back on and rock it for another 5. Of course you want to print 100% infill.
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