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Crazy no start issue for 73 JH # 12265  Rate Topic 
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 Posted: 05-18-2019 07:55 pm
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cjwilson
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Hey guys, trying to resurrect #12265 after 10 years of hiding in the garage. Had to rebuild fuel tank and repair a few pinholes. New fuel pump and 2 fuel filters, 1 at tank and 1 at carbs. Once that was good, I put about a gallon of gas in and got her to fire. After a bit of tinkering and adjusting, it would run without assistance until I shut it off each time for about a week.

As of yesterday, the gallon of fuel was used up. It actually ran dry. I put 5 gallons in. Car then wouldn't start. In the interim, I replaced a few vacuum lines around the carbs.

Still won't start. It turns over then fires right away, but will only run for about 1 second. No choke or gas petal manipulation makes any difference. I can see linkages moving when I pump and pull them.

I pulled each plug and they are getting fuel. I pulled the central fuel line into the carbs and let the pump flow into a jug. It's got plenty of flow. I didn't check pressure, but can.

I also installed a new speedometer cable in the interim. I had to pull the dash part way out to do it. I don't think I knocked any wires loose while in there but who knows.

Is there a wire behind the dash that can cause this?

Maybe both carbs clogged due to running out of gas?

Anyone have any great wisdom they can bring to bear? I'm scratching my head!

Last edited on 05-18-2019 10:33 pm by cjwilson

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 Posted: 05-18-2019 10:28 pm
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cjwilson
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Updates: I checked fuel pressure at the carbs - 6.5psi

I checked compression - #1-93psi, #2-93psi, #3-104psi, #4-97psi.

I also checked spark at #1 and it's hot and bright.

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 Posted: 05-19-2019 02:02 pm
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Brett Gibson JH5 20497
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Fuel pressure Way Way high, should be 2.5 to 3.0 max. compression low, did you open the carbs "barrel" so the engine could breath when checking compression. Points or electronic ignition, and yes a loose wire behind the dash can shut you down.
Brett.

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 Posted: 05-19-2019 02:15 pm
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cjwilson
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To add to this... I checked for spark again. Strong spark that stops as soon as I let off the key. So spark is happening while the starter and key are engaged. But when I let off the key so the car can continue running there is no spark.

And this is probably why the car died initially. I assumed it ran out of fuel but probably didn't.

Key switch issue? Anyone know how I can test?

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 Posted: 05-19-2019 02:29 pm
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Brett Gibson JH5 20497
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No, wire issue, you don't have a hot wire going to the ignition system after start and in the run position, had the same issue years back, but without having a wiring diagram in front of me right now can't pin point it for you, I do re-call having to run a new wire rather then pulling the whole mess apart looking for the break. But still look behind the dash you may get lucky and find you have a loose contact, the switch rarely goes bad.

Brett

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 Posted: 05-19-2019 08:41 pm
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Dakota123
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Maybe the ballast resistor? Drops the voltage to 9? 10? Volts after start. On my MK1, it’s mounted to the firewall near the coil. Try jumpering around it and see if it stays running, maybe.

Last edited on 05-19-2019 10:48 pm by Dakota123

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 Posted: 05-20-2019 01:31 am
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Tim Murphy
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Here is a link to a JH wiring diagram done by John R Kimbrough several years ago. This should help. Take care. http://www.jhppg.com/assets/Wiring%20files/JH_wiring.pdf

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 Posted: 05-21-2019 01:06 am
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cjwilson
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Hey Brett,

Thanks for answering. Yes fuel pressure is higher than I expected. Pump is newly purchased and installed. I purchased at a local "box" auto parts store and it was labeled as 3-4psi. I'll see about putting a regulator in line.

I think compression was registering lower than actual. Battery was a bit low while I was cranking. Carbs weren't open but I'm not too concerned with compression. I was just checking to see if I lost a cylinder...

Points.

And I found the problem. She's running great once again. It was indeed a loose wire in the 5 way connection mounted on the firewall. It was the white wire which supplies power to the coil from the key. It was still inside the connector but had backed out far enough to not make a connection.

Thanks!
Chris

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