I have a 1981 vette with a 5.7 it don't have any spark when turning over then when I shut the key off it fires one cylinder what would cause this
Ignition switch,bad fusible links, coil,ignition module. I have replaced several switches for this problem. At the coil, when you turn the switch on, there should be power. There also should be power when trying to start the engine. If there is no power while cranking, replace the switch. The reason it hits a cylinder or two is that the power goes to the coil, just not enough to get the engine running..
SOURCE: Cylinder #3 miss fire and the engine light comes on
I would also check the #3 plug as well, maybe by replacing it with an old plug for a few trips to see if the problem is gone.
I don't know what kind of plugs you use but I stopped using Champion plugs years ago after buying four and having two of them with cracked insulators and doing pretty much what you describe.
It was at first only bad mornings when one or both would misfire until the engine warmed them a little and cooked the overngiht moisture out of them.
I didn't replace the wiring first though, since the problem only came up after doing the 'right' thing, replacing plugs that had 30-40,000 on them.
SOURCE: 1993 Chevy Cavalier 2.2 not firing on 2 cylinders
The reason I'm asking this is because a dual coil fires BOTH plugs at the same time. If one plug doesn't fire right, the other won't either, even to a point that neither does. Kepp the coils where they are and swap the plugs and wires and see if you have a change. Let me know
SOURCE: 1993 Chevy Cavalier 2.2 not firing on 2 cylinders
you can test it but removing wires on the coil. they should have same strength as 1 and 4. if they are weaker then you have a bad coil. if nothing happens your have a bad module.
if you want put the 1,4 coil on the suspected bad tabs on the module and see if spark is same strength.that should do it. you pretty much did the right thing is swaping with what testing equipment you have to work with.
its most likely a bad module though. very common. when you test something always have someone explain how its tested and how it works.
Michael
ASE certified
SOURCE: NO SPARK
HAVE YOU CHECKED YOUR TIMING BELT? IT MAY HAVE BROKEN. OPEN THE OIL FILL CAP AND LOOK TO SEE IF THE CAM IS MOVING WHILE AN ASSISTANT IS CRANKING THE ENGINE!!! IF NO TURNING OF THE CAM HAPPENS THEN YOU HAVE A TIMING BELT FAILURE!!!!! WE HOPE THIS HELPS YOU FIND THE PROBLEM
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