73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: buddy84GMC on April 25, 2008, 08:00:30 pm
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I have an 84 Sierra with a small block 400 in it with HEI. It stopped running when it wanted to shift, but that had nothing to do with it when I pulled a spark plug wire and no spark. I ran down to Advance and got a new coil and still no spark. The old coil witch was really only 1,300 miles old had a scroched wire so I thought that was the problem. Changed the coil and tried to wiggle all the wires connecting to the leads. Nothing works. I have to go back tomorrow and put a test light on it. Any tips on what each side of the coil wires are? The red I would imagine is the power source, and the yellow one, I have no clue. If I hook the test light up to it, the red wire should be hot with the ignition turned on, but not cranking??? The yellow wire may become hot once it crank, but not sure. I looked at the rotor as well and it looks fine. Its new as well. Thanks for any help.
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With the key on the red should be hot (even when not cranking, but the key must be in the "run" position)
Make sure the red on the coil lines up with the red in the module plug
the yellow is the ground
My 82 had the HEI with the ESC (electronic spaek control)
I converted it to the 3 wire normal HEI
You may have an issue with the Module or the ESC box or the condensor
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timing chain?
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timing chain?
I had that happen once :)
pull the cap and turn the key to crank
no rotation from the rotor is a sure sign
but it may be a sheared gear pin
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Good idea about the cranking with the cap off. I will head back out there in the morning and give it a try and test the wires. If all goes well and I figure it out...some neighbors are getting a wake up call! I will post back what it was if I figure it out. Any other pointers??? Thanks again
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If the engine sounds normal during cranking and you have B+ at the ignition coil then check the ignition module and the pick up coil. Disconnect the pigtail at the module and measure the resistance of the pick up coil. spec is 500-1500 Ω typically you'll find 800Ω on a good one. If the pick up coil is good replace the module.
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I have done everything I can with the distributor on. I got a new coil, had the control module checked and its good. Cleaned up the plug prongs for the module and tried again..still no spark. It could be the pick up wires under the distibutor. I wiggled them and they seem to be in tact, but I was told they can break off under that plate I guess where the bearing is. Thats where I am at right now. Might have to get it towed and pull the distributor off and check the pick up wires. Any other ideas would help since I am stumped, especially if those wires are good. The rotor turns when cranked as well. Thanks
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I replaced my 25 year old HEI with one of these
http://cgi.ebay.com/ebaymotors/SBC-BBC-CHEVY-HEI-DISTRIBUTOR-RED-8908-R_W0QQcmdZViewItemQQcategoryZ33690QQihZ015QQitemZ250241458008
It took a little tuning to get it right (lighter advance springs etc...)
Been in the truck for 8 or 9 weeks now, so far so good
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Thanks. Not bad considering the coil I just bought cost just as much! I would like to solve the problem first and find a reason to buy a new distributor. Once I find the problem and if it needs replaced...I would go for that one too! Thanks
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You talked about having the module checked, but did you ohm out your pickup coil? We just went through that with ours, and the pickup coil was bad. I decided to replace the distributor since it was 29 years old, and I figured that if I had to disassemble it to replace the coil, I'd just replace everything. Good luck!
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Provided you have 12 vdc to the unit,
Theres only 4 or 5 things that can go wrong with the HEI (electrically)
1. coil
2. Module
3. condensor (you should change this when you change the module)
4. the coil under the reluctor (I just measured the resistance on a "known" good unit- 830 ohms at the module plug (unplugged))
5. ESC box (on Electronic spark controlled trucks)
(I have no clue how to check the ESC box)
Do you have the ESX box?
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how many times did they check the ignition module? sometimes you have to check it repeatedly to make it fail. gotta get it good and hot. anyhow, if your pick-up coil tests good, you probably need to just bypass the ESC...good luck
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Not too sure if I have an ESC but I saw the condenser and that can be replaced for $5. All I can say about the ESC is that my truck has a double plug in piggyback to the one that goes into the control module. I do not know if that could be the ESC?? The control module was tested 3 times in a row and passed all 3. They did say they needed to do it a few times to let it warm up. If the ESC is a box...I didnt see it in there. Thanks
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an ESC module looks like this and can be found on the firewall somewhere near the distributor...
(http://chevythunder.com/esc_module.jpg)
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Great. Thanks a lot. I will yank that off too and see if I can get it checked at Advanced. Is there any chance that the control module can test ok, but not work when on the truck? I am tempted to buy one and try anyways. One last try on before I have to take the distributor out and check the pick up wires to see if they snapped off.
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If it was a factory 84, it has ESC, it was standard on all trucks. Not a 400 didn't come it in though, so you would think the ESC was gone. How may wires does your distributor have on it for the coil plug? That is an easy way to tell if it has ESC. If you find it does have it, and it is possible based on the way it is acting, you should just bypass it completely.
Read this for reference:
http://73-87.com/7387garage/drivetrain/escrepl.htm
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Thanks a lot. Thats good to know since my 400 should not have an ESC and I know my distributor has wires going to the computer above the glove box. I traced those wires to see if they were broken before I took the control module out of the dist. If I am not mistaken, the ESC should be the 'computer' above the glove box and it has a long parallel port similar to what you see on computers; right???
The only thing I can say is that there were no signs of the truck ever going to stall or the pick up wires being broken since I was told the truck would have seemed to miss as the distributor rotated which would have been the wires being snapped off when the engine was accelerated. The truck shut down when I accelerated, but there was no signs of hesitation before that. So, if the pick ups are ok, then I can lean towards this ESC issue. What are the chances the ESC worked before with my 400 and all of a sudden does not anymore? Could it have shorted out? I can bypass it and this seems to be my last resort if the pick up wires are not broken. I have not pulled the distributor yet, but hope to in the next day or 2. Thanks for all the help again.
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The box above the glovebox is the ESC on carb'd vehicles. the likelyhood of it dying all of the sudden it not out of the ordinary.
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I did what the article Chris posted said and still no good. I bypassed the ESC and soldered the 2 wires that needed put together and plugged the pink ignition wire directly to the BAT terminal. Gave it a try and still no start. I will have to have the coil checked and the control module again. Could it be the pink ignition wire gone bad? Maybe snapped off somewhere, but not sure if that would cause all this. Thanks for any more pointers.
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If the engine sounds normal during cranking and you have B+ at the ignition coil then check the ignition module and the pick up coil. Disconnect the pigtail at the module and measure the resistance of the pick up coil. spec is 500-1500 Ω typically you'll find 800Ω on a good one. If the pick up coil is good replace the module.
did you do this?
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I tried to that a few days ago after trying a new coil. I do have a voltmeter but am not sure how to read it well since there is no 800 on the Ohms scale, but I have to figure out how to convert the reading I guess. The manual sucks and does not explain a thing. It does sounds normal when cranking though. I will try to read the meter again but I know I am missing how to multiply something to get the actual reading I need. Its an old one and a crappy one at that. Thanks
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The wire connections on the magnetic pickup wires inside the HEI distributor of my 1990 c1500 are intermittent. I occasionally lose spark, and have to remove distributor cap, and wiggle the two yellow wires that connect to back of the ignition module under the distributor cap. Then I'm good for a few months to a year. Then it does it again. Really irritating. I have another distributor to put in when I get the chance. Maybe give those wires a wiggle and see what happens.
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Why not just replace the pick up coil rather than wiggling the wires and hoping it doesn't fail you again? It's a $12 part.
Buddy:
You can't read ohms scale on the volts scale. Select the 2KΩ scale if it's not auto ranging and measure across the two leads when you disconnect them from the module. Post your results.
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Why not just replace the pick up coil rather than wiggling the wires and hoping it doesn't fail you again? It's a $12 part.
Everything under the cap is a big ball of rust, truck has 250K miles on it now, was waiting for another distributer to swap the whole thing out. I just picked up a good used one last weekend for free. :)
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I did what I could and it did not give me a reading. I know it worked 2 days ago, but I was in a hurry to get down to the store have the control module tested again and it passed 5 times. I bought a pick up coil in case since the only thing left to do is take the distributor off since I cannot find a way to get the voltmeter to give me a reading.
One other comes to mind...I did bypassed the ESC by following the article and I know it did it right, but the one thing he never mentioned was about plugging anything back in or cutting the blue wire that goes in front of the started on the knock sensor. Thats the only one thats still conected to the truck, but disconnected at the computer ESC. There is still the vacuum line for from the ESC vacuum switch that is still connected as well to the carb. Should I block this off??? What about that blue wire to the sensor? Still having no spark and I am pretty sure the pick up coil wires are in tact since I have wiggled them before and they did not pull out or seem damaged, I have a few more questions. What about my control module...It had 5 prongs 2 on one side and 3 on the other. The yellow wire is the middle prong but thats part of the connector I disabled coming from the ESC. Should I replace the control module with a 2 and 2 prong one??? I have no clue, but I did disconnect that harness from the ESC. I put the 2 wire green and black together like I was supposed to as well as part of bypassing the ESC. I just hope I did not miss anything. I bought the pick up coil and it has only 2 prongs to plug into and my old was has 3 since the control module has 3 prongs...I might have to take a picture to show you what I mean. let me know if you need a photos of my setup. Seems to me like its a little different than others. Thanks
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I was on the 73-87 site and found out that if I get no reading from the pick up...might be the culprit. I mean there was no reading at all, but I ran the meter on my control module and it gave no reading but did 2 days ago...I will replace the batteries and give it a try again. Still puzzled on how I am going to plug the new pick up coil with 2 inlets into the control module with 3 prongs?
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pictures please
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There are two color codes for the in-cap ignition coils:
Red and Yellow wires Used on vehicles that use the Yellow coded pickup coil.
Red and White wires Used on vehicles that use the Blue/Black, or Clear pickup coils
These coils may have different color codes, but NONE OF THEM is a HIGH PERFORMANCE/BETTER/FASTER/MORE POWERFUL version of another. You don't get stronger sparks with a yellow-coded set than the others. The ONLY difference is that when you pass an electric current through them, they produce a magnetic field in opposite directions. Note that for the Blue/Black and the Clear color coded pickup coils, the lead wires and the plastic connector (if used) are arranged in such a way that the wires must be crossed in order to connect them to the module. The Yellow-coded pickup coil wires plug in without crossing. This maintains proper ELECTRICAL polarity, while allowing reversed MAGNETIC polarity. And magnetic polarity is only important at low engine speeds, (especially cranking) because of electrical interference from the starter or perhaps the alternator--If the interference is "just right", the module gets a false trigger signal. Using the correct magnetic polarity pickup coil can eliminate the interference, and the correct magnetic polarity ignition coil is needed to match the pickup coil. You "can" mis-match the parts, but don't complain if the engine takes longer to crank or misfires during cranking.
Look at the wires for the pickup coil
on a vacuum advance disty they move back and forth millions of times because the coil is connected to the vac advance. (the one in the pic is locked in place)
(http://www.mez.co.uk/dcam/DSCF0326.JPG)
The thin pickup coil lead wires have had a history of failure due to the motion of the vacuum advance. The problem often starts showing itself as the engine dying, then running, then dying, then running, etc. When the vacuum advance moves the pickup coil to a certain position, the broken conductor inside the insulation of the wire disconnects, and the engine dies. When the engine dies, vacuum is reduced, the vacuum advance relaxes--and the broken wire re-connects and the engine runs again.
the plug should be disconnected from the module to test
mine read 830 ohms
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Try this test
hook up a wire to the disty
using a female spade connector
connect to your battery
now try it
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Here is my set up. I would have to think that the pick up coil they gave me was wrong even though I had the control module right there with me. I almost need an double ended pick up coil to make this work. The pick up coil connector is located between the control module and the wires that came from the ESC that I modified by cutting and crimping the 2 cut wires together like I was supposed to. Let me know what you think. Thanks a lot.
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The brighter yellow connector is the pick up wire connector; it has the 3 prongs in the male and female ends. The new pick up coil is the one on the table with the control module. The new pick up coil would not let me plug the modified connector (darker yellow) into it.
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Take a small screwdriver or awl and push the female connectors out of the plastic piece on the new one (try pushing them out of the old one first)
now you can put them in the old plastic piece
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Try this test
hook up a wire to the disty
using a female spade connector
connect to your battery
now try it
I tried it all. I tested the new pick up coil and did the same test on the old one...no response. I guess the wire may have split inside the insulation. It would not make a complete circuit so it must be broke. I never got that hesitation on and off symptom that usually is the result of this happening...I will have to replace it and see. Thanks a lot for the help. Let me know about the 3 prong set up in my photos. Hopefully the correct pick up coil connector is available.
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You bought the wrong pick up coil unless you are going to install a 4 pin module.
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Yeah, so my question is...if I bought a new module, can I buy a 4 pin and everything work out ok. There is still that first connector that has 3 pins that plugs into the pick up before it plugs into the module. I will get the correct 3 pin pick up coil first and try that. If I still have problems after that, I will wonder if bypassing the ESC caused anything to not work even though I followed the directions to a T. It will take me a couple days to get to my truck, but I will post what happens. Thanks a lot
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Bypassing the ESC only eliminated the computer. It shouldn't make a difference in functioning.
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Unless the computer went bad, but in this case it must not have since it did not work after bypassing the ESC. Headed down to see if the pick up coil I need is the original style from an 84 GMC and my truck had a 305 originally.
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Words of wisdom I learned the hard way... If the module checks out bad, it's bad. But if the module checks out good, it may still be bad.
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Words of wisdom I learned the hard way... If the module checks out bad, it's bad. But if the module checks out good, it may still be bad.
Thanks. I think I am just going to pull it and replace the pick up anyways, and if that still does not work, I will replace the module. I still have no reading when I hook my meter up to the pick up so it should be replaced anyways. Looks like a 24 year old 85,000 mile pick up. Saves me hassle in the future if its even slightly worn out. Thanks
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Finally got to work on the distributor. Replaced the pick up coil and found that the tape wrap that holds the wires to the pick up itself was dry rotted and completely flaked off. That being said, I tested the old pick up and no reading...just got to find my 4 coil screws and I'm set. I also found out the dist. was installed 180 degrees the wrong way. I fixed that too and have to redo the wires. Can't believe it was mickey moused like that. The whole truck was rigged up like it was made from stolen parts from 4 different kinds of intake bolts to backwards valve cover to a bad valve job with no rollers...and now this! Glad I got it all taken care of as I found it. Hopefully not too much more will surprise me. Thanks for all the help. If I get it running, I will post it and if I dont...look for a new post!!!
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well, good luck man...i'm sure you'll get it taken care of...
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Thanks for the help. I got spark, but no start. The coil is grounding out for some reason; I have a blue spark going to the coil where the BAT wires are. I checked for bad wires, etc. Any ideas what is causing it to ground to the coil? Thanks. I stopped trying so I dont ruin the coil
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Did you replace the button under the coil?
back on page 1, I recomended one of these...
you may want to take a look
http://cgi.ebay.com/ebaymotors/SBC-BBC-CHEVY-HEI-DISTRIBUTOR-RED-8908-R_W0QQcmdZViewItemQQcategoryZ33690QQihZ015QQitemZ250241458008
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Did you replace the button under the coil?
back on page 1, I recomended one of these...
you may want to take a look
http://cgi.ebay.com/ebaymotors/SBC-BBC-CHEVY-HEI-DISTRIBUTOR-RED-8908-R_W0QQcmdZViewItemQQcategoryZ33690QQihZ015QQitemZ250241458008
I did replace it last year, but if it was bad would I be getting spark? The spring on it is good and it makes contact from what I can tell. If I bought that distributor you mentioned, then I would have to take the whole ESC system off and drain he antifreeze due to some valve or switch near he starter and I would be out $40 on my new coil and pick up. I will get to the bottom of this hopefully without buying a new distributor since I have to take the ESC completely out to install the one you recommended. Thanks a lot though and I will not pitch that idea, I just know it can run without that for now...just need to find time to figure it out. thanks again
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You have spark but the coil is grounded? ??? Very confused as to what it's doing.
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You have spark but the coil is grounded? ??? Very confused as to what it's doing.
Maybe I can take a video and post it on youtube. I have never had this happen before, but I will try the old rubber cushion that the coil button goes through since the new one seems to not let the spring through all the way...but it seems to still make contact to me. Let me know if you want a video and I can try to post that tomorrow night if I can.
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Did you replace the button under the coil?
back on page 1, I recomended one of these...
you may want to take a look
http://cgi.ebay.com/ebaymotors/SBC-BBC-CHEVY-HEI-DISTRIBUTOR-RED-8908-R_W0QQcmdZViewItemQQcategoryZ33690QQihZ015QQitemZ250241458008
I did replace it last year, but if it was bad would I be getting spark? The spring on it is good and it makes contact from what I can tell. If I bought that distributor you mentioned, then I would have to take the whole ESC system off and drain he antifreeze due to some valve or switch near he starter and I would be out $40 on my new coil and pick up. I will get to the bottom of this hopefully without buying a new distributor since I have to take the ESC completely out to install the one you recommended. Thanks a lot though and I will not pitch that idea, I just know it can run without that for now...just need to find time to figure it out. thanks again
You don't have to remove/plug/unwire anything
this is how easy it is:
Remove old unit
install new unit
hook up one wire (the red one plugs right in)
start truck
drive away happy
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lol! I hear you! I am stubborn I guess, but I will get it running. Just got to get it running soon since I am blocking my fathers Buick in from cruising! If I get fed up, I will probably give in and try to sell the parts I bought on ebay or somethin. I actually do have a used distributor I can throw in it from a good engine its just at someone elses house. I might try that and if it runs, I will buy that one you told me about.
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Buddy, I quickly read through this post. I saw in the first one that you said "it shut off when it went to shift" (so you have personally had this running), later you said "the distributor was 180* out". This is not adding up, In working with the distributor did you install it 180* out or have you never pulled it since it quit running? Explain this in more detail & maybe we can get to the bottom of it all. Is the truck coughing, chugging, spiting up the carb or anything? I just noticed your other post, I hadn't realized this was the same truck. Are you sure that someone didn't put a timing chain in wrong, put the distributor in wrong to "fix" it & now you have "unfixed" it? Was it EXACTLY 180* out or maybe the timing chain jumped as was mentioned? Lorne
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Buddy, I quickly read through this post. I saw in the first one that you said "it shut off when it went to shift" (so you have personally had this running), later you said "the distributor was 180* out". This is not adding up, In working with the distributor did you install it 180* out or have you never pulled it since it quit running? Explain this in more detail & maybe we can get to the bottom of it all. Is the truck coughing, chugging, spiting up the carb or anything? I just noticed your other post, I hadn't realized this was the same truck. Are you sure that someone didn't put a timing chain in wrong, put the distributor in wrong to "fix" it & now you have "unfixed" it? Was it EXACTLY 180* out or maybe the timing chain jumped as was mentioned? Lorne
Thanks! To clear things up..the truck is 180 degrees out and I never knew it. It was running and then just shut down as I was shifting, but then I found out I had no spark, so I guess the shifting part has nothing to do with it. I never had the dist. off and found out it was 180 off when it pointed to 6 at TDCC on cylinder 1. That would make it 180 degrees off and the timing chain is ok and so is the marker on the balancer. Since it was 180 off it did not match up so I was on here asking questions and I checked it after I was told how to check for 180 off...everythings ok now. I had no spark and found the pick up coil to be no good so I replaced it and want to now put the dist in the correct way with the rotor pointing to cylinder 1. I did that, and still no start chug or anything, just a solid crank. I checked for spark with the screwdriver on the intake and held it close to the dist and it did arc so I have spark...but when I had the wires all hooked up it seems like its grounding at the coil or back to the coil since there is a nice blue spark going over or through the BAT wire on the coil itself. Its not sending the spark down the spark plug wire for some reason. Kinda bizzare but I have never seen this before. Wires checked out ok so I am stumped. Still have not had time to get a good friend of mine to check it out. I hope tomorrow (Tuesday)to have him come over and check it out for me. I will post any thought he has or any questions. Thanks
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I am totally lost here. If your distributor was 180° off you wouldn't have been driving in the 1st place. If you have spark blasting out of the top of the distributor I can't help but wonder if you put the coil in upside down somehow.
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I am totally lost here. If your distributor was 180° off you wouldn't have been driving in the 1st place. If you have spark blasting out of the top of the distributor I can't help but wonder if you put the coil in upside down somehow.
A vehicle can run with the dist 180 off. You just adjust the wires to make it run...and someone did. Thats how I found out it was off. Someone also posted that same statement on here somewhere. the coil can only go in one way, its HEI. The 3 wires on the coil would not let the coil lay in the dist if it were upside down. I'll hopefully get to the bottom of it tomorrow evening. Thanks
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With a GM HEI it doesn't matter as long as it's in the proper firing order. When you say the distributor was 180° off that's making us believe you had the distributor installed on TDCE with the wires arranged correctly.
So are you saying you checked for spark at one of the cap terminals? I hope you realize that if you crank it with the wires off you are going to send the coil firing voltage to max and the path of least resistance is going to be a crossfire either through the coil or through the distributor base which will spike your ignition module and burn it up lickity split. Never crank it with the wires off. You should be checking for spark at the end of the wire boot one at a time.
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Like Vile said, if it is 180 out, it is 180 out. You can drop a distributor in a motor with the cannister on drivers side and as long at the #1 cylinder is fire at the correct post it doesn't matter where it is. Ditto on the firing with no wires, not a good idea.
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FINALLY! :o Long story short...it was 180 out but only after I was told by someone to rotate to the next stroke. I was right originally, but its fixed in that respect at this point. Next, still no go and that lovely blue spark on the coil was the wires on BAT (red) side that has a crack in the insulation straight from the coil. That arced and thats why I had a blue spark. Exchanged the brand new coil and it fired right up. Advanced the timing a little and its perfect. No pinging or anything. Had the carb adjusted after that so I took it for a run and it screams! A little better than before, feels like more response when I give it gas. Should run better now its all back where it was meant to be. Word if advice from this...ALWAYS CHECK THOSE CHEAP WIRES ON A NEW COIL! It literally broke where it comes right out of the coil; its filled with a shiny black substance that the wire was formed into so you have to be careful not to bend the wire at that point or it will crack, and like mine did, break off. The wires on the coil are a one piece wire, not a bunch of small ones spun together so its not very flexible. When I got my new coil it did not have those 3 wires placed into the holders that keep them in place. May have been a returned one that made its way back to the shelf. Anyways, I appreciate all the time and effort everyone put into helping me out! Its been a long 3 and half weeks, but it running like old times again; just had to find time to get the help to sort it all out. Hope this post helps someone out someday. Take care! Thanks again
John