Need Help!
Thread Starter
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Senior User
Joined: Aug 2010
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From: Sandy Level
Need Help!
My 78 400/4speed 4x4 coils acting stupid.
Background
I just put a timing chain, cam, Plugs, cap, wires, rotor and lifters.
I get it all back together, get it ready to turn over but know fire. I checked the coil she is getting 5.4 volts to her but when you turn the key she fire once when you first hit the key before the motor turns and once when you quit. Every once in a while it will fire right. I replaced the coil still the same. I have swap the ignition boxes both blue wire. Replaced the harness going from the dizzy/coil to the ingition box still know change.
Help please!
Background
I just put a timing chain, cam, Plugs, cap, wires, rotor and lifters.
I get it all back together, get it ready to turn over but know fire. I checked the coil she is getting 5.4 volts to her but when you turn the key she fire once when you first hit the key before the motor turns and once when you quit. Every once in a while it will fire right. I replaced the coil still the same. I have swap the ignition boxes both blue wire. Replaced the harness going from the dizzy/coil to the ingition box still know change.
Help please!
Thread Starter
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Senior User
Joined: Aug 2010
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From: Sandy Level
This has to do with the fire coming from the coil. It will not fire expect when you just start to hit the key.
Rusty Roller
Joined: Oct 2011
Posts: 1,423
Likes: 5
From: Santa Cruz Mountains
First things first... Put a test light on the positive side of the coil that you can see from the cab. Key on, do you have power? Then see if you have power when cranking it over. If it doesn't then it's possible that your ign switch is bad.
If it does have power then move it to the neg or dist side of the coil and see if it flashes while cranking. If it does then the problem is elsewhere.
Make sure you are on the compression stroke of number 1 cyl and the rotor is pointing to the number 1 plug wire.
Let us know the results.
.
If it does have power then move it to the neg or dist side of the coil and see if it flashes while cranking. If it does then the problem is elsewhere.
Make sure you are on the compression stroke of number 1 cyl and the rotor is pointing to the number 1 plug wire.
Let us know the results.
.
Thread Starter
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Senior User
Joined: Aug 2010
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From: Sandy Level
I checked with a multimeter and have 5.4 volt when key on and around the same when cranking, that is touching both pos. and neg side of coil and same time. I just don't get any fire threw the coil old or new expect when the key is first on and when you turn off I get a spark through a plug hooked to the coil wire.
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Senior User
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From: Sandy Level
When I pulled her down to swap the timing chain and cam the only thing I un hooked was the dizzy. Everything else I laid to the side hooked up.
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Thread Starter
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Senior User
Joined: Aug 2010
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From: Sandy Level
No spark when turning over but a spark as soon as you hit the key and when you let off the key.
Rusty Roller
Joined: Oct 2011
Posts: 1,423
Likes: 5
From: Santa Cruz Mountains
Well you just might have a bad ign switch. Pull the 12v power lead off the coil and temporarily jump 12v from the batt positive to the pos side of the coil and crank her over. My self I just jumper without removing the other wire but it's not mine....
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Senior User
Joined: Aug 2010
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From: Sandy Level
The key cylinder was replaced but not the switch. I'll try the above tomorrow after work. Would it be best to hook it to the starter side of the selinord or straight to the battery.
Rusty Roller
Joined: Oct 2011
Posts: 1,423
Likes: 5
From: Santa Cruz Mountains
You would want constant batt power; not switched for the test. But something you could easily remove if it starts because you will need to remove it to stop the engine.
I think my jumping without removing the 12v already at the coil back-feeds power to the ign system. It didn't have any ill effects for me but others might not recommend this method. A better way would obviously be to replace the ign switch. But if it fires up then you know for sure. I put about 35mi's on mine hooked up that way before replacing the switch... Use your older ign box for this test if you decide to.
I think my jumping without removing the 12v already at the coil back-feeds power to the ign system. It didn't have any ill effects for me but others might not recommend this method. A better way would obviously be to replace the ign switch. But if it fires up then you know for sure. I put about 35mi's on mine hooked up that way before replacing the switch... Use your older ign box for this test if you decide to.