1998 holden statesman with starting issues and dying while driving

[Maree H]

Hi there, I would love for some help been a female. Awhile back I had an issue with my holden. So a new water pump was installed, also a new power steering pump, harmonica balancer and all new belts. When I went to get it back from the mechanic it would't turn over after he had water blasted the engine bay. On return to collect car I also had to pay for a coil pack. Any way after that the car was having issues with starting etc. sometimes would sometimes wouldn't. Found that the alternator wasn't holding charge so purchased a brand new one and had that replaced. The car has sentimental value to me so im trying my hardest to get this sorted before I give up all hope. Since having the alternator replaced the car was not driven much due to it needing to have the breaks bleed as had air pockets in them. So it sat there for a 1month. Oh trying to start it again not power. Managed to jump start it. Drove for 20-30mins then to gas station to top up gas turned of car. Would start at all, pushed it out of way of pumps. Tried jumping starting and nothing! went back that night to try jump start it. And pop started sweet when jump starting. Anyway went to use it yesterday had to jump start it AGAIN. Went about 4kms up the road I noticed all the dash computer board flicking on and off. Then the engine light came on. From that point I tried to turn the car around as I did so the car died on me. We had to push it of the road. We left it for ages on jump starter leads and finally it started but died twice on the way back home with in the 4 km distance. the battery is new and a heavy duty one. Could I be looking at a solenoid issue? could the harmonica balancer be out? could it be the battery terminals themselves as they look a bit soft in appearance? Could the alternator not be working or not installed correctly by mech even though its new? im so lost right now some advise would be awesome thank you. Also i noticed the battery was taken out on a Monday fully charged put back in car on the Tuesday and car turn on straight away. We left the battery un connected to keep it charged. When I went back and connect terminals Wednesday it started I left car running for about 15mins again then drove to gas station. turned car of and nothing no lights no click not nothing!!