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crazyvwvanman
Samba Member
Joined: January 28, 2008
Posts: 9939
Location: Orbiting San Diego
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 Posted: Thu Feb 02, 2023 5:24 pm Post subject: Re: Got a "No Start", Pump Relay Term 87 voltage always On? |
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Yes, that voltage would be expected.
You should have done 2 measurements with the relay removed.
Between relay socket pin 30 and chassis ground. (12v)
Between relay socket pin 87 and chassis ground. (0v)
Pin 30 should always have near battery voltage, compared to chassis ground.
When you measured between pin 30 and 87 the pin 87 acted as a "ground" for the meter probe, connected through the fuel pump windings to the fuel pump ground.
Voltmeters when set to volts don't allow any real current to flow so the pump wouldn't run though the voltage reading on the meter might lead you to think it would be able to.
A similar concept applies to your measurement of the ignition coil pin 15.
Yes, it could appear the be "ground" under certain meter setting.
Since it connects to several things that also connect to ground it would show a low resistance to ground through those things.
Once the key is on that pin 15 gets and holds 12v because all those several "grounds" are too weak to drain much of the voltage away.
Sorry if this isn't a very clear explanation.
Mark
| Steve M. wrote: |
.....
Getting back to this voltage I have removed the Fuel Pump Relay and measuring from Relay term. #30 to #87 it is showing battery voltage 12.96v.
That Fuel pump is not running as I had a quiet moment to hear it. |
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Steve M.
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Joined: July 30, 2013
Posts: 6833
Location: Fort Lauderdale, Fl.
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| Posted: Thu Feb 02, 2023 8:32 pm Post subject: Re: Got a "No Start", Pump Relay Term 87 voltage always On? |
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| crazyvwvanman wrote: |
Yes, that voltage would be expected.
You should have done 2 measurements with the relay removed.
Between relay socket pin 30 and chassis ground. (12v)
Between relay socket pin 87 and chassis ground. (0v)
Sorry if this isn't a very clear explanation.
Mark |
Clear enough for me to understand it. I understood it for the 87 through the fuel pump wiring. I had the Bentley with me today so I could following wiring paths to see the grounding of the coil through 15.
I'm trying to understand the coil windings. I thought they were separate windings... been too many years from the classroom.
I believe I did 30 and Gnd. 12.96v Don't remember 87 & Gnd.. Think I did it as I was measuring everything, but with the relays installed.
What's got me thinking is why the resistance readings on the coil between #15 & #1 and between the terminal going to the Distributer were the same on my spare coil as on the "bad" coil, but the spare coil starts the engine? Yet, I was getting spark off the "bad" coil?
Thanks for your input.
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djkeev
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Joined: September 30, 2007
Posts: 32632
Location: Reading Pennsylvania
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michaelasnider
Samba Member
Joined: September 27, 2013
Posts: 369
Location: East Kootenays, Canada
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| Posted: Mon Feb 06, 2023 6:57 am Post subject: Re: Got a "No Start", Pump Relay Term 87 voltage always On? |
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| Steve M. wrote: |
What is the resistance supposed to be on this coil? I'm getting 000.7 to .9. |
Curious if you measured the secondary resistance and if so what you got (between the coil negative and the HT terminal with the plug wire lead)?
The primary resistance spec is 0.52-0.76 ohms on the primary, so I'd be surprised if your measurements were preventing a start, as I was having no starting issues with a primary measurement of 1.1 ohms. |
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Steve M.
Samba Member
Joined: July 30, 2013
Posts: 6833
Location: Fort Lauderdale, Fl.
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| Posted: Tue Feb 07, 2023 5:29 am Post subject: Re: Got a "No Start", Pump Relay Term 87 voltage always On? |
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| michaelasnider wrote: |
| Steve M. wrote: |
What is the resistance supposed to be on this coil? I'm getting 000.7 to .9. |
Curious if you measured the secondary resistance and if so what you got (between the coil negative and the HT terminal with the plug wire lead)?
The primary resistance spec is 0.52-0.76 ohms on the primary, so I'd be surprised if your measurements were preventing a start, as I was having no starting issues with a primary measurement of 1.1 ohms. |
quote="michaelasnider"]
| Steve M. wrote: |
What is the resistance supposed to be on this coil? I'm getting 000.7 to .9. |
Curious if you measured the secondary resistance and if so what you got (between the coil negative and the HT terminal with the plug wire lead)?
The primary resistance spec is 0.52-0.76 ohms on the primary, so I'd be surprised if your measurements were preventing a start, as I was having no starting issues with a primary measurement of 1.1 ohms.[/quote]
This something of a mystery to me as I was getting spark the the #3 plug.
After measuring and seeing readings I didn't think it was the problem.
On a hunch I connected my spare to the wires and bingo -start on first crank.
Maybe it was just "moving" a wire and it gave a better connection? My terminals were all clean and the wire
I've been busy at work so maybe later today I can check the resistence of the old coil again later today. I didn't write the measurements when I did it, but thanks for the spec's on it.
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DanHoug
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Joined: December 05, 2016
Posts: 4800
Location: Bemidji, MN
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| Posted: Tue Feb 07, 2023 6:41 am Post subject: Re: No Start - Pump Relay Term 87 voltage always On [SOLVED] |
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coils live a high stress life, needing to contain tens of thousands of volts in a very small space. simple resistance checks investigate but one thing that can go wrong-- open or shorted windings, but so much relies on the high voltage insulation that can test fine with an ohm meter but jump gaps once it gets all excited.
since there is no good test method, this is a case where when in doubt, you just replace.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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michaelasnider
Samba Member
Joined: September 27, 2013
Posts: 369
Location: East Kootenays, Canada
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| Posted: Tue Feb 07, 2023 6:49 am Post subject: Re: No Start - Pump Relay Term 87 voltage always On [SOLVED] |
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| DanHoug wrote: |
coils live a high stress life, needing to contain tens of thousands of volts in a very small space. simple resistance checks investigate but one thing that can go wrong-- open or shorted windings, but so much relies on the high voltage insulation that can test fine with an ohm meter but jump gaps once it gets all excited.
since there is no good test method, this is a case where when in doubt, you just replace. |
Yeah, fair enough. An easy and inexpensive spare to carry. |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2325
Location: Bay area CA
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| Posted: Tue Feb 07, 2023 9:33 am Post subject: Re: No Start - Pump Relay Term 87 voltage always On [SOLVED] |
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Resistance measurements on a coil are a good first step to test for open-circuit, but useless to test for a shorted turn. If just one turn in either the primary or secondary has gone short to a neighbour, then the inductance plummets, and the coil won't produce any spark.
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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Steve M.
Samba Member
Joined: July 30, 2013
Posts: 6833
Location: Fort Lauderdale, Fl.
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| Posted: Tue Feb 07, 2023 7:19 pm Post subject: Re: Got a "No Start", Pump Relay Term 87 voltage always On? |
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| michaelasnider wrote: |
| Steve M. wrote: |
What is the resistance supposed to be on this coil? I'm getting 000.7 to .9. |
Curious if you measured the secondary resistance and if so what you got (between the coil negative and the HT terminal with the plug wire lead)?
The primary resistance spec is 0.52-0.76 ohms on the primary, so I'd be surprised if your measurements were preventing a start, as I was having no starting issues with a primary measurement of 1.1 ohms. |
Reading tonight at a lower temperature across the primary terminals the reading I get in ohms with the meter in aito mode is 001.1 dropping to 000.8.
Okay the neg. lead to the secondary HT center to either the pos. or neg terminals is 4.02-.03.
Seems to be a bit low if the info I found about testing coils was accurate saying it should no lower then 11.0 and normal around 13. or better.
So if my quick measurements of the coil I put in were the same - how is it running?
Or in my haste to get it done I made a mistake?
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