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Good spark at coil but weak to no spark to plugs.
2002 Chevrolet Silverado 3500

Good spark at coil but weak to no spark to plugs.

(2002 Chevrolet Silverado 3500)
I have replaced ignition module twice and the truck will start once and not restart again. I have good spark coming from coil but weak to nothing at any of the plugs. When I first turn the key to start I get one to two sparks weak then dies out. I have replaced cap,rotor,pickup in distributor, whole distributor, crank sensor, two ignition module and the coil. All grounds have been cleaned and power is going to all sensors.thanks for all your help.
Tags: this is a w 4500 cab and, chevrolet, silverado 3500
1 answer & 6 comments
Popular Answer
on June 11, 2019
REPLACE distributor cap AND rotor !

Start engine and drive vehicle..

Happy motoring!
Sign in to reply
on June 11, 2019

Coil supplies spark to distributor cap - rotor then sends spark to spark plugs via plug wires.

Is is doubtful all plug wires are defective.

More likely still a cap & rotor malfunction. - OR - there IS simply insufficient spark from coil.

**At over 40 kv - Spark from coil should easily jump a 1 inch air gap to metal ground!**

IF you do not have that much spark from coil - replace ignition coil ..

Some aftermarket parts are junk..

Specific procedures that are ‘out of the norm’ MUST BE FOLLOWED when replacing these distributors !



on June 11, 2019

Hint when installing distributor using conventional method of # 1 @ tdc - compression stroke :

Correct ROTOR to number one spark plug wire position is not where it seems to be - carefully examine distributor can top to bottom..

It can be a bit confusing.

Good luck!
on June 12, 2019
Cap and rotor check out good with ohm meter. I have several new caps and rotors and does not change anything. Good spark at coil but when I turn key I might get half a spark then dies out at any of the spark plugs.
on June 12, 2019

‘IF’ you have spark from coil that will jump a 1 inch air gap to a metal ground and make a audible popping sound each time the coil fires - that leaves nothing but a distributor cap OR rotor problem - there’s simply nothing else it can be!

DO YOU GET THAT KIND OF SPARK FROM COIL WIRE - that goes to the dist cap ??

(Even if the distributor was installed out of time - engine should at least backfire)

I just don’t think the coil is producing enough spark - I’ve had new coils that were defective right out of the box..
on June 12, 2019
I pulled #1plug wire from cap and placed a spark tester on the cap and it fired up so I shut it off and plugged plug wire back to cap and restarted the truck. It ran a little rough but smoothed out at higher RPM.i replaced distributor and used a timing light and it is off but when you rotate the distributor the timing mark doesn’t move on the balancer turn the other way and it finally dies. The owners of this truck said some mornings it will not start and today it is warm and sunny. I have been dealing with this for two weeks. How do you time these, with a scan tool and engine over 1000 RPM. I bet this won’t start tomorrow because of rain.
on June 15, 2019

Yes professional quality scanner is necessary - it’s called > crankshaft variation relearn procedure.

Google it.

Scanner will also display all required step by step procedural information on screen.

Good luck to ya there Dan.
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on June 11, 2019
REPLACE distributor cap AND rotor !

Start engine and drive vehicle..

Happy motoring!
Sign in to reply
on June 11, 2019

Coil supplies spark to distributor cap - rotor then sends spark to spark plugs via plug wires.

Is is doubtful all plug wires are defective.

More likely still a cap & rotor malfunction. - OR - there IS simply insufficient spark from coil.

**At over 40 kv - Spark from coil should easily jump a 1 inch air gap to metal ground!**

IF you do not have that much spark from coil - replace ignition coil ..

Some aftermarket parts are junk..

Specific procedures that are ‘out of the norm’ MUST BE FOLLOWED when replacing these distributors !



on June 11, 2019

Hint when installing distributor using conventional method of # 1 @ tdc - compression stroke :

Correct ROTOR to number one spark plug wire position is not where it seems to be - carefully examine distributor can top to bottom..

It can be a bit confusing.

Good luck!
on June 12, 2019
Cap and rotor check out good with ohm meter. I have several new caps and rotors and does not change anything. Good spark at coil but when I turn key I might get half a spark then dies out at any of the spark plugs.
on June 12, 2019

‘IF’ you have spark from coil that will jump a 1 inch air gap to a metal ground and make a audible popping sound each time the coil fires - that leaves nothing but a distributor cap OR rotor problem - there’s simply nothing else it can be!

DO YOU GET THAT KIND OF SPARK FROM COIL WIRE - that goes to the dist cap ??

(Even if the distributor was installed out of time - engine should at least backfire)

I just don’t think the coil is producing enough spark - I’ve had new coils that were defective right out of the box..
on June 12, 2019
I pulled #1plug wire from cap and placed a spark tester on the cap and it fired up so I shut it off and plugged plug wire back to cap and restarted the truck. It ran a little rough but smoothed out at higher RPM.i replaced distributor and used a timing light and it is off but when you rotate the distributor the timing mark doesn’t move on the balancer turn the other way and it finally dies. The owners of this truck said some mornings it will not start and today it is warm and sunny. I have been dealing with this for two weeks. How do you time these, with a scan tool and engine over 1000 RPM. I bet this won’t start tomorrow because of rain.
on June 15, 2019

Yes professional quality scanner is necessary - it’s called > crankshaft variation relearn procedure.

Google it.

Scanner will also display all required step by step procedural information on screen.

Good luck to ya there Dan.

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