GMC Wont Start Unless Get A Jump

crazieone67

Everyone keeps saying its nt the battery or alt its the fuel pump pressure or some thing else bt why does it crank when u jump it then it will run all day long dnt need no more jumping

Mr_Shiftright

If what you're saying is this: "Battery dead in the morning, jump starts okay, runs all day, then next dead again...."

if that's what is happening, it's not your alternator. Most likely culprits are either a) the battery, or b) a parasitic drain on the battery that sucks out its charge that accumulated during the day.

So you have to have the battery "loaded tested" (which can only be done on a battery that has been properly charged in the first place) and if that checks out okay, then you have to diagnose for a "parasitic drain", which can be tested in the manner described below:

Testing for Parasitic Drain