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Need new coil, go with stock or aftermarket?

Discussion in 'The Garage' started by dawson444, Mar 8, 2005.

  1. dawson444

    dawson444 1/2 ton status

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    After talking to someone about my problem with my truck not starting, he said try replacing the coil. Do you guys think I should just go for a stock one or get an aftermarket one? I am running the stock dist and Taylor wires. It is a 355 TBI, with vortec heads and a mild cam (GM Crate 350HO). Thanks for any input!
     
  2. Fierospeeder

    Fierospeeder Banned

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    i would buy a stock.
     
  3. mouse

    mouse 1/2 ton status

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    stock
     
  4. Goober

    Goober 1/2 ton status

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    The stock HEI coil is actually overkill for most stock engines so replacing a bad coil with a stock unit is the cheapest and best way to go.

    That being said, don't try to fix something that might not be busted unless you have an unlimited source of funds. If that is the case, buy a new loaded distributor for about $200.

    There are a bunch of things that can cause a truck not to start and a handfull of those (including the coil) are in the distributor. Why not find out whats busted so you only have to replace 1 thing?

    First, make sure you have 12 volts going to the distributor. Put a multimeter (if you don't have one go buy one. You can get one that will be adequate for working on your truck for under $20) on the positive teminal (BAT) on your distributor. Got 12 volts?

    If you have the correct voltage going into the distributor then you need to check if you have a spark. Remove a spark plug wire and insert a screwdriver or any other metalic conductor into the plug boot. Using insulated pliers, hold the screwdriver ¼-inch away from the engine block while cranking the engine over.

    Got spark? You have just ruled out an ignition problem and don't need to buy a new coil.

    No spark? You need to check the rest of the ignition system.

    Start with the simple stuff. Grab your mulimeter and set it to the low scale. Connect the leads across the BAT and TACH terminals and check your reading. If it's over 1 Ohm your coil is toast. Replace it with a stock unit.

    If the reading is less that 1 Ohm then you need to switch the multimeter to the high scale and connect one lead to the BAT terminal and the other lead to the carbon button that sits on your rotor inside the cap. Check your reading. Switch the first lead to the TACH terminal and recheck. If either of these reads 6000 - 30000 Ohms your coil is perfectly fine. If both tests read zero continuity (infinit resistance) then replace the burned up coil.

    If those readings are good then take a look at your cap. Is it cracked? Is there a bunch of carbon tracking all over the inside? If you think anything looks funny get a cap and rotor kit, they are cheap and need to be replaced every year or so anyways depending on how much you drive. While you are there make sure your rotor turns when the engine is cranked. :doah:


    The only other things you can check in the distributor are the pickup coil and your module.

    Remove the green and white leads from the module and grab your trusty multimeter. Connect one lead to ground (engine block, manifold, etc.) and check the green wire then the white. You should not see any continuity here. Move the vacuum advance back and forth a bit if you don't get a reading right away. If you do get a reading then either your pickup coil or your module have been melted into a solid block of junk that needs to be replaced. I usually choose to replace both since they are relatively inexpensive and if one got blown up then the other may have been damaged. Buy a stock, General Motors module! Follow the installation instructions EXACTLY! Use heat-conducting paste on the back of the module! There are a bunch of expensive "super-duper" modules out there that may provide some benefit over 6000 RPM but they do it at the expense of lower RPM performance.

    If your readings from ground - green and ground - white are good (no reading or infinit resistance) then check resistance between the green and white leads. Your reading should be between 500 and 1500 Ohms. If it is then your module is bad. If your reading is not between 500 - 1500 Ohms then your pickup coil is bad.



    Disclaimer: I am not a mechanic .... but I did sleep at a Holiday Inn Express last night. :D These are the steps I take when testing HEI distributors as I've fixed a few of them over the past 30 years in my cars and trucks.

    Good luck and have fun.
    :waytogo:
     

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