Mechanic Job in Ishpeming, Michigan

At first it was a charging issue. New battery ran dead but would run after it was jumped. I put a new alternator on but was only getting around 13v when revved. Then, battery died and now even while jumping it it will crank but no start. Engine is a 440. Wiring is simple but a few attachment to the rv coach batteries make ot difficult for me. Motorhome is parked on a 40 acre camp and can be worked on at any hour. Was running great until last week.