v-8 swap now no start - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 07-17-2003, 10:51 PM
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v-8 swap now no start

I swapped out my 4 cyl in my 86 CJ to an AMC 8 cylinder. Finally done and now it won't start. It turns over but no fire. This is what I have found out so far.
At the coil, with the stock harness pulled from coil I read 12 volts. Once I put the harness over the coil, I read 6 volts? Now I thought that it should still be 12 volts? I tried 2 coils and got the same results. Both coils were working. The 4 cylinder ran before I pulled it. I think the problem lies somewhere within the coil/distributor? I had to splice my wires for the distrib. to reach, but I solder everything and made sure it was correct. I even twisted the wires like stock. I checked for spark and I am not getting any. This 8 cylinder also ran before I pulled it an d I am using all the equipment from it.
What can I do from here? Should I try to run the coil straight from the battery and see if it starts? Why is it dropping voltage at the coil when connected? Can I have something miswired? Any help would be great. John.
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post #2 of (permalink) Old 07-18-2003, 10:53 AM
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Re: v-8 swap now no start

</font><blockquote><font class="small">In reply to:</font><hr />
Once I put the harness over the coil, I read 6 volts?

[/ QUOTE ]1. If you put the harness back on the coil and turn the ignition key to START mode ( Starter Cable removed to prevent starting),
2. There should be 12 volts at the coil.
3. If in the RUN mode position, a resistor is switched in,
4. And the voltage drops to about 8 volts. </font><blockquote><font class="small">In reply to:</font><hr />
I had to splice my wires for the distrib. to reach, but I solder everything and made sure it was correct.

[/ QUOTE ]5. It's likely that this is the problem...
6. Double check the wiring, for a wiring error.
7. Did you match wire colors?
8. or did you use a schematic?
9. What igntion module are you using?
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post #3 of (permalink) Old 07-18-2003, 11:38 AM
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Re: v-8 swap now no start

Your getting no spark from coil to dist? Or no Spark from Dist to Plugs? I'd recheck all your wiring thats prob where your problem is and like Leve is getting to what ignition module do you have? I had to go through about 2 of them when I had a similar problem. You could go get the Ignition Module tested I believe at Autozone. Or just buy another they are a dime a dozen.
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post #4 of (permalink) Old 07-18-2003, 03:01 PM
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Re: v-8 swap now no start

Ok this is what I did with my results.
With a helper, I had her crank the engine over.
I read 9 volts during the cranking process. In run I read 6.5 volts. The 6.5 volts is normal in run my book says. The 9 volts during cranking is not, it should be 12 volts.
Odd thing, with my spark tester, essentially a spark plug lookijng device with an adjustable gap, I get spark when vehicle goes from run to off. I get no spark during cranking. Only when the vehcile gets switched from run position to off, and it's a nice spark.
So what should I do now? My book doesn't say how to troubleshoot this problem. Please help as I want to get this out of my garage so I can move on to other things. Thanks, John.
post #5 of (permalink) Old 07-19-2003, 12:00 PM
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Re: v-8 swap now no start

Bumping my results back up.
post #6 of (permalink) Old 07-19-2003, 01:14 PM
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Re: v-8 swap now no start

1. Charge the battery,
2. It will load down when cranking.
3. But, to have a good spark... the battery should be fully charged.
4. If it hasn't been charged,
5. Charge it.
7. You describe a spark when switching the ignition key from run to off.
8. Is that correct?
9. But no spark in either RUN or START mode?
10. I would suggest you use a grounded spark plug and a plug wire,
11. Rather than a "spark device",
12. Only because I don't know what you're using...
13. I do know what a spark plug and wire is...
14. Does the negative side of the coil go to the ignition module? This provides negative return for the coil. The coil is NOT grounded.
15. If you put a test lamp on the negative side of the coil and crank the engine
16. does the test lamp flash?
17. If it ain't flashing you've got: [*] A bad pick-up in the distributor [*] A bad ignition module or, [*] The distributor is not turning or, [*] A combination of the above.
18. Have you had the ignition module tested?
19. Have you had the coil tested?
20. Have you had the pick up module tested?
21. All these parts can easily be tested at the Auto-Parts store...
22. These tests give a General indication...
23. When you turn off the ignition...
24. In essence you're doing what the Ignition Module does...
25. It's just un-controlled.
26. So I'm leaning toward the ignition module.
27. Or a wiring error.
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post #7 of (permalink) Old 07-19-2003, 02:30 PM
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Re: v-8 swap now no start

Have you checked your fuses. Did a carb swap on my 86 and when all finished had the same spark problem- No spark while cranking one strong flash as you stop cranking. After hours of trying to figure out what was wrong I finally looked at the fuses and replaced the bad one (can't remember what one) and the engine started on the first crank.
post #8 of (permalink) Old 07-19-2003, 03:43 PM
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Re: v-8 swap now no start

Stop chasing your tail!
The problem is simple-your ignition modual has a ground wire, with out it-jeep no work!
In my C-J7 I went one step ferther and put a switch in to cut the groud for a cheap alarm. With out this groud even someone who knows all about AMC would be stumped because as you have found everything apers normal. Good luck! [img]images/graemlins/beach.gif[/img]
post #9 of (permalink) Old 07-19-2003, 03:53 PM
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Re: v-8 swap now no start

1. Welcome to the forum.
2. Please complete your user profile:[*] It's a nice thing to do.[*] It's helps to know who we're talkin' to.[*] It helps to know what's your ride.[*]It helps to know the local in which you live.

3. Read the New Posters Message at the top of the forum.
4. Participate! Two brains are better'n one!
5. So Spoon...
6. What makes you so sure your answer is the only correct one?
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post #10 of (permalink) Old 07-20-2003, 07:50 PM
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Re: v-8 swap now no start

Ok, this is new info I have found out. As a note, the distributor cap is off, so I can vewrify that the rotor is spinning. The battery is fully charged and I have gone over the grounds and cleaned them up. Now, I went to the auto store and the guy talked me out opf buying an ignition moduel. He said bad grounds, don't waste your money. This is what I did with my results.
I still had no spark what so ever.
I grabbed a spare AMC 304 distrib. that was hanging around.
I connected it into the harness and with the igniton switch in the run position, nothing happened UNTIL I moved the shaft and grounded the distrib.
Now with the pick-up lined up with the rotor, I get a spark at the plug. This only happens when I break ground and reground.
So if I spin the distrib. while grounded, nothing happens. But if I spin it while switching my ground wire on and off, it sparks.
SO, I guess the pick-up in the distrib. that is IN the motor is bad. I can replace that. But does this verify a bad ignition modual or something else. I was happy to see a spark, but now I don't know.
I plan on buying a new pick-up (or taking the one out of the spare distrib.) and buying a new igniton modual. Do you think this will solve the problem? Thanks, John.
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