Methodically track down reason for no spark

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Jun 12, 2004 | 08:22 AM

don_79f250

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Methodically track down reason for no spark

Gentlemen,

MY '79 f20 won't start. It turns over perfectly. Carb smells of gas when I pump it. But when I pulled a plug and held it close to the block, there appearsto be no spark. Just put in brand new plugs, wires, distributor cap and rotor. It's been a long time since I debugged an ignition system, and thought it might be useful here to initiate a step-by-step methodology for tracking down a no-spark fault on older trucks.

So, my step 1: pull a plug and hold it close to the block while cranking to check for spark.

Jun 12, 2004 | 08:37 AM

Clifford11

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Joined: Jun 2004

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From: Kenabeek, Ontario

The first thing to check is the ignition module, my '79 4wd went through a lot of them in a short period of time. Try checking the coil too.

Jun 12, 2004 | 08:43 AM

Greg 79 f150

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From: Kentucky

Was the engine starting and running o.k. BEFORE you put in the tune parts ? I am no mechanic but is sounds like after re-checking all of your new components again for proper orientation, and it still has no spark, it could be a bad coil, ignition module, or your Duraspark power box located on your fenderwell is bad. (assuming you have Duraspark ignition of course) good luck

Jun 12, 2004 | 11:03 AM

Ecuri

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Joined: Jun 2003

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From: Houston/Hope BC

There is a schematic at this site that should tell you all you need to know, if the module or the coil don't do the trick:
http://www.jason.fletcher.net/tech/d.../duraspark.htm
GL

Jun 12, 2004 | 05:10 PM

lastchance

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Joined: Apr 2001

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From: South Central PA

It never hurts to try the ignition module, they go out without warning! If you're not carrying a spare it would be a good $25 investment even if it isn't the problem!! I shut my truck off at the drive-thru at McDonald's once because the girl at the window couldn't hear me over the exhaust. Went to start her back up, just cranked, wouldn't start. Took my wife longer to undo her seat belt and move her purse so I could fold the seat front to get my spare than it did to pop the hood and plug in the other module lol!!!

Jun 12, 2004 | 11:25 PM

1991fseries

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From: Barrington USA

my method is start at the battery and trace the wires from there to the spark plugs testing each connection along the way once you have no electric current you know which part has failed you takes a little time but works all the time

Jun 13, 2004 | 03:19 AM

whd507

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Joined: Jun 1999

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From: SW Missouri

if it turns out to be the module, add a separate ground strap to one of the mounting bolts, to the cab. I have had this problem many times. bad ground.