My 1999 GMC Jimmy has a rough start takes longer than normal to start after sittings overnight or while at work what could be causing that It has a brand new fuel pump?

Answer 1

I have a similar problem but it isn't the spark plugs. The car just won't crank after sitting outside when the temperature is low. It has a new battery (the battery is good) and starts fine when you jump it. The voltage meter then runs higher than normal and slowly drops back towards normal after a while but never returns all the way to what is normal (13.8 volts is normal, I believe) . Something is draining the battery as it sits overnight. No lights or any other type of accessory is left on. Recently, after being driven 200 miles it was parked, in the cold, for about a half hour, and I had difficulty starting it. After holding the key in the start position for some time I got it to turn over enough to start.

you might want to check your spark plugs, slow starts when cold sometimes can be caused by a less than optimal spark.

Might check Distributor cap / Rotor button, I have to replace mine at least once a year.