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Post by class115 on May 29, 2018 10:01:30 GMT -5
My 74 would crank and crank and backfire through the exhaust. Enough one time that it expanded the muffler. Turned out to be an intermediate short in the ignition module. Put in a spare one and never had the problem again. The way I found out it was that was my spare was prettier and when I swapped them the problem went away. Bob Bob, Thanks, By ignition module do you mean ECU? I've got a 1-year-old ECU and swapped it for another older one I had in the parts bin. But, a prettier one new one should arrive today. we shall see Vic
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Bob
Settling In
Posts: 193
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Post by Bob on May 29, 2018 10:12:01 GMT -5
My 74 would crank and crank and backfire through the exhaust. Enough one time that it expanded the muffler. Turned out to be an intermediate short in the ignition module. Put in a spare one and never had the problem again. The way I found out it was that was my spare was prettier and when I swapped them the problem went away. Bob Bob, Thanks, By ignition module do you mean ECU? I've got a 1-year-old ECU and swapped it for another older one I had in the parts bin. But, a prettier one new one should arrive today. we shall see Vic Yes, the ECU. The one I had in it was pretty new also. A bad ground on the ECU would cause problems also.
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Post by class115 on May 29, 2018 21:10:50 GMT -5
No volunteers to check for spark tonight. Planning ahead in case I needed to change the starter relay, ordered this but didn't see the box until it came in. I'd pay a premium for the option to buy an American made one.
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DynoDave
CO-ADMINISTRATOR
Motown Mopar-Wizard
Posts: 11,150
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Post by DynoDave on May 30, 2018 11:04:31 GMT -5
Get that kid in your avatar to hold the spark plug wire when you crank the engine over.
Or is that you?
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Post by class115 on Jun 1, 2018 17:36:26 GMT -5
Still no joy-
I used a spark checker and got a spark from the coil wire, I put in a new ECU and a new Starter relay. It will still turn over, sound like it wants to start and then die when I let go of the ignition switch.(I'm NOT pumping the gas anymore to avoid the backfire) I am not a mechanic, but I know how to listen to those who are smarter than me. Does this narrow it down to the starter switch? Or is that just not a factor. To recap, I changed the fuel filter, plugs, rotor, cap, ECU, ballast resistor, and starter relay. I see a spark form the coil wire with the spark tester while cranking. Where should I look next? thank you Vic
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Post by 71greengo on Jun 1, 2018 20:04:46 GMT -5
Still no joy- I used a spark checker and got a spark from the coil wire, I put in a new ECU and a new Starter relay. It will still turn over, sound like it wants to start and then die when I let go of the ignition switch.(I'm NOT pumping the gas anymore to avoid the backfire) I am not a mechanic, but I know how to listen to those who are smarter than me. Does this narrow it down to the starter switch? Or is that just not a factor. To recap, I changed the fuel filter, plugs, rotor, cap, ECU, ballast resistor, and starter relay. I see a spark form the coil wire with the spark tester while cranking. Where should I look next? thank you Vic timing chain
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Post by class115 on Jun 1, 2018 20:37:42 GMT -5
OK, timing chain. I did check TDC on the number 1 cylinder and got the piston up, close to 0 on the timing mark, and the rotor on the number 1 spark plug, all at the same time. Is this good enought to clear me of a timing chain issue? I was hoping it was, but the hope is not a strategy:-( What other evidence of a timing chain issue do I look for? one truck expert in my area thinks I jumped a tooth, that's why I looked at TDC/rotor/timing mark
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Post by class115 on Jun 2, 2018 13:21:24 GMT -5
If I can find a local old-school mechanic, how do I approach them? I know enough not to be invested in my own theories Do I just say it doesn't start or do I recommend they start where I left off- I haven't verified that the timing didn't jump. Or did I? I live in southern Maryland, so if anyone knows anyone around me who can figure this out, they'll have my business! .
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Tom
CO-ADMINISTRATOR
Itching to get back to posting!
Posts: 737
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Post by Tom on Jun 2, 2018 13:44:45 GMT -5
If you find a mechanic, I would simply tell them that you want a no start diagnosis.
Using the spark checker to check for spark out of the coil wire was just a start... You may now want to use that spark checker to check for spark at the plugs. (end of plug wires)
That way you are determining whether spark is somehow "lost" inside cap. That can happen with bad cap/rotor (which i believe you replaced) or IF for some reason the distributor is not rotating. Had that happen to me on an old Ford once.....drove me nuts for awhile.
One question you had remains unanswered..... While I did initially think "timing chain" I kind of put that out of mind when your compression numbers were "ok" I could be wrong.....but I would have expected poor compression on a jumped time no start. Again, I could be wrong.
This gives me opportunity to tell a war story. LOL While working as auto-Tech, I had a no start diagnostic on a Ford product. Think it was a Contour.
For some reason, I initially thought it was a fuel issue.......
So as a shortcut...I sprayed some starting fluid in the throttle body... Attempted to start it......and BOOM! it blew the air box off the car, over my head, and bounced off the wall about 25 feet high, behind me. LOL Scared the living daylights out of me. Had to change my drawers, LOL
Turns out the timing belt was stripped but not broken.
As you would turn it over....it would get close enough to being in time to try and start/run. Then it would get further away as you cranked.
Another van I was working on.....I sprayed starting fluid down the throttle body.
Inside the van, with the "dog house" off
When I attempted to start, it back fired a fireball straight up into my face.
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Tom
CO-ADMINISTRATOR
Itching to get back to posting!
Posts: 737
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Post by Tom on Jun 2, 2018 15:10:06 GMT -5
Another test
You need a voltmeter for this one.
Check voltage at coil + terminal while cranking
also check voltage at same place with ignition switch in run position.
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