I have a 1990 Dakota 3.9 L that was running fine until I changed the plugs.
Started up fine after changing the plugs and ran / started the rest of the day with no problem. The next morning truck would not start, put a neon type timing light on just to check for spark, no spark. removed dist cap and rotor and reinstalled, engine started right up. Truck ran fine all day, next morning had the same starting problem and resolved by same method.Have now replaced dist cap & rotor but experienced the same morning starting problem.
The weather has been hot and dry, I am tempted to replace the plugs with the old ones but would really like to figure out what is going on.
Thanks
RGO

I have a 1990 Dakota 3.9 L that was running fine until I changed the plugs.
Started up fine after changing the plugs and ran / started the rest of the day with no problem. The next morning truck would not start, put a neon type timing light on just to check for spark, no spark. removed dist cap and rotor and reinstalled, engine started right up. Truck ran fine all day, next morning had the same starting problem and resolved by same method.Have now replaced dist cap & rotor but experienced the same morning starting problem.
The weather has been hot and dry, I am tempted to replace the plugs with the old ones but would really like to figure out what is going on.
Thanks
RGO

the pick up in the distributor might be bad. may be even the module.

First, I tried using platinum sparkplugs and had the same problem, mis-fires quicker than engine is designed for. Humad condition helps it even worst.
Second, re-evaluated your wire setup. which wire goes to which cylinder.
Third, I had to go back to original (plain) sparkplugs.:banghead: