73 SB no spark

[GratefulPhish]

Back again...

I’ve been chasing this issue for a few months dealing with intermittent starting issues. Replaced the idle solenoid, accelerator pump, plugs and wires, removed the aftermarket digital ignition with a Bosch coil, adjusted the valves, etc.
it started two days ago reluctantly after finally jumping it with my other car. Tonight it started without jumping and drove fine but wouldn’t start after sitting for three hours. Tried and tried but it seems I’m not getting a spark. I think I’ve narrowed it down to the ignition switch? Not sure where else to go with this...I’m ready to put a for sale sign on it.

[VW_Jimbo]

You can bypass the ignition switch to test. Sounds like it may be going bad.
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[Igpoe]

Are your battery posts clear of corrosion? Ground strap on clean metal, etc?
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'73 super.

[GratefulPhish]

Brand new battery, battery cables and ground, yes. Thanks!

[GratefulPhish]

Started today within seconds of being jumped by my other car. Symptomatic of a failing ignition switch?

[Igpoe]

Old battery with weak cells. Check alternator output next time you jump it off
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'73 super.

[GratefulPhish]

Brand new battery

[Starbucket]

Run a jumper wire from battery + to coil + and start it (remove jumper to stop it), this will tell you if it's the switch.

[GratefulPhish]

Do I need to disconnect anything from the coil to do this?

[Starbucket]

[GratefulPhish]

Thanks, I think Ashman may have made this suggestion or something similar in another thread.

[Starbucket]

[ashman40]

From your descriptions I take it the ignition switch will get the engine cranking without any problem, but for some reason it appears there is no spark reaching the cylinders?

Start by testing the voltage at the ignition coil #15 (+) terminal. Test with the ignition switch in the ON/RUN position. Then test while the key is in the START position (might need a buddy for this test). Not uncommon for the ignition switch to work while in the ON/RUN position but not provide current WHILE in the START position. All your testing while standing behind the engine will not help since it is only an issue while the key is in the START position.
A similar issue is when the voltage is fine while in the ON/RUN position but the voltage drops while the starter is cranking the engine. If the voltage at the ignition coil drops below 10.0v the coil could stop firing. If you have an electronic ignition and the voltage drops below 11.0v the module may stop working.
Test and report back the voltage at the coil when the key is in both positions.

Also test the voltage at the battery terminals when it is at rest, while the ignition switch is ON and while the starter is cranking the engine. The starter is the #1 larger current drain on the battery. While it is cranking the engine most of the battery’s current is being pulled thru the battery cable to the starter motor. The voltage of almost every other device on the car will drop while the starter motor is cranking the engine. Report back the voltage reading at these three states.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[Cusser]

I'm good at auto electrical, but I typically do not post often about that, I wait for Ashman to reply, as he is more patient with folks.

And - to be blunt - Ashman does a better job of this all than I do.
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[stevebaz]

try viewing this.
https://www.youtube.com/watch?v=EiEzQktOPP4&t=1394s

[GratefulPhish]

Bypassed the ignition switch this morning as mentioned above and it started right up! Hoping the ignition switch was the problem all along.

Appreciate all the patience and support!

[VW_Jimbo]

It was!

These cars are famous for bad switches! I have replaced thousands of them!
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[GratefulPhish]

I’ve been hunting this ghost for 3 months