86 4.9 Ignition Problem
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86 4.9 Ignition Problem
Hello. Tonight I took apart my 4.9 to do lifters. Everything went smooth, Until it was time to start it up and now I have no spark. I have power at the coil, I have run, start, and ground at the distributor. I checked both sides of every fusible link I could find. I checked the compression just to make sure they didn't give me the wrong push rods or something stupid and it has 135 pounds so it's not that. It gets fuel so I am stumped. Any help would greatly be appreciated. Thanks
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Check all the wiring around the TFI module, for possible damage. Did you unplug the module or remove the distributor when doing the work? Remove the plug wires etc? If so check the firing order and make sure the wires are hooked up correctly.
Did you confirm a no spark condition by testing?
Did you confirm a no spark condition by testing?
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I only took the plug wires off the plugs. I didn't pull the cap or anything. I wiggled and pulled on everything and it didn't make a difference. I looked for ground wires that I thought maybe I left off but everything looks good.
Post Fiend
Joined: Jul 2004
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From: Northern California
Yeah check the firing order for the plugs, and wires, if you haven't thought of that.
The only other thing I can think of is to do a Computer diagnostic.
There is also a Wiggle test you can perform through the computer to test loose connections.
It's possible that your ignition module failed or something, as well. But it would be an odd coincidence.
More likely something happened while you were doing the work, but you can never tell.
The only other thing I can think of is to do a Computer diagnostic.
There is also a Wiggle test you can perform through the computer to test loose connections.
It's possible that your ignition module failed or something, as well. But it would be an odd coincidence.
More likely something happened while you were doing the work, but you can never tell.
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If you put a screwdriver into a spark plug boot and hold it near a ground while somebody tries to start the engine, you don't get any spark?
I've read on here problems where a wire's insulation (not spark plug) gets melted or worn away and it sporadically shorts out to ground.
I've read on here problems where a wire's insulation (not spark plug) gets melted or worn away and it sporadically shorts out to ground.
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Post Fiend
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From: Northern California
You will have to strip the harness down.
The easiest for me to find wiring faults is to remove the harness and move it to my bench if it's small. The TFI-IV wiring harness is small enough to do this. Unplug it from the distributor and ignition module, then unplug it from the main harness. First I'd check continuity of all the wires in the harness. With a Ohm meter + lead on one side of the circut or wire, and the negative side on the other side, and if one fails, I unwrap the black protective layer and fix it, then rewrap it with black electrical tape.
Some places can test TFI-IV ignition modules. Just to eliminate it from the possibilities, I would have it tested if I could.
The easiest for me to find wiring faults is to remove the harness and move it to my bench if it's small. The TFI-IV wiring harness is small enough to do this. Unplug it from the distributor and ignition module, then unplug it from the main harness. First I'd check continuity of all the wires in the harness. With a Ohm meter + lead on one side of the circut or wire, and the negative side on the other side, and if one fails, I unwrap the black protective layer and fix it, then rewrap it with black electrical tape.
Some places can test TFI-IV ignition modules. Just to eliminate it from the possibilities, I would have it tested if I could.
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I went on ALLDATAdiy.com :: Leading Source of Diagnostic and Repair Information and paid the $28 one year subscription fee for My Year and model. I found all the wiring diagrams and printed them out and then pulled the connector from the EEC-IV and all the other ends from the sensors and so forth. I pulled all the loom off of the harness and started tracing the wires from one end to the other as per the diagram and tested for continuity. I found the loose junction of 5 wires connected together and reconnected them and it fired right up. What a difference the new lifters made. Thanks for all the suggestions.
