Weak spark on every plug, but truck runs fine

Maintenance/Repairs
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1

I have a 2001 Sonoma with a 4.3 Vortec. I noticed all my plugs were shooting weak sparks while trying to figure out why it wasn’t starting. It turned out to be my fuel pump. Still all my sparks are very orange. Could this be affecting my performance? It seems to run fine. Does it mean my coil is going to go out soon. Any advice would be appreciated. I’m pretty new to this. Thanks

2

Well as they say if it’s not broke don’t fix it. If it runs fine, good for you. Coils normally don’t give warning signals but just quit but not very often. Only once have I replaced one that was actually bad and that was on my lawn mower, but go ahead and put a new one on if you’re worried.

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3

Are you sure the plugs were grounded - not just dangling - when you saw weak orange spark?

4

Not for sure. I had them touching the engine. They were resting on it. Could a dirty engine make a weaker spark? There is quit a bit of gunk built up on it.

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5

Dirt and gunk can prevent good solid contact. Look at how much surface area of a plug securely contacts the engine. Can you run a good fat wire from the negative battery post or a bolt on the engine? Then clamp that wire and the spark plug - maybe with a vice grips. Set the spark plug on an insulated surface like rubber or dry wood. Stand back and turn the key to Start and see what you’ve got.

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6

Thanks I’ll try that out when I get a chance

7

You might make sure the engine itself has a good ground. The negative battery cable solidly and cleanly attached to the engine block as well a a ground strap to the chassis from the engine. This stuff corrodes over time and the electrical path grows in resistance.

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8

have someone test the spark using an oscilloscope. Or you might get an old plug of any type and gap it out to .065 and see what the spark looks like on it.

9

I see no problem to solve here. No codes, no rough running, nothing. Why pursue it?

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10

Curiosity? I wouldn’t pay someone to do it, but if I have the time I like to figure things out.

11

You’ll only see that bright blue spark if you’re using a decicated spark tester

We have tons of GMs of various vintages in our fleet, including lots with the same 4.3 V6 that you have. And we’ve replaced MANY fuel pumps, but almost no coils at all

To translate . . . don’t bother replacing the coil based on what you perceive to be a weak spark

don’t waste your money fixing a problem that doesn’t exist

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12

I’ll take that back. My Olds Aurora with the Northstar engine required replacing the coils from time to time but that was a known issue. Might want to just buy a spark tester.