1987 e350 351 v8 ambulance van has issues starting
First post here, hoping for some luck. I bought this ambulance van to convert to live in and the inside is decked out but i think she needs love under the hood. Had trouble starting when i bought it but we jumped it and it drove well, and i got a deal so i went with it. When i went to pick it up the guy had charged up the battery and she started right up, then started for a few days after that, with all electrical stuff working fine. Then went out one day and wouldn't start. Took the battery in for testing and it started spewing battery acid out so i replaced it with a nice deep cycle. Started right up for a while, but i wasn't driving it lots. Drove it around town for a full day running errands and had an engine flush and rear dif with an oil change. Radio blasting, blinkers working, felt great. Next day went out and no start. Turned over maybe 3 times then nothing. Just so happens this was the weekend we were moving out of our house and i to the van. Tried to get a mobile guy to come troubleshoot but he flaked out on me. Got a jump, had to charge for a while but she started. This was at night and with headlights on we only made it a few blocks before she started shutting down. Lived at a park for a few days then got another jump, this time blinkers didn't work and radio wouldn't come on. However volt meter went up when i stepped on the gas so alternator seems to be working. I'm going to hook up the second battery (unhooked right now) and see what happens. But if it turns over and shows voltage increase when given gas, what could be pulling so badly on the battery that it can't hold enough charge to start? Any ideas would be hugely appreciated. Thanks!
You would seem to have a parasitic draw, big enough to draw the battery down in short order. If some or all of the ambulance stuff is still in place I'd suspect one of those electrical components to be the culprit. Do a test to see what is causing that draw---anything one amp or higher will drain a battery over 24 hours without any problem.
Even though your voltage meter shoots up under acceleration that doesn't necessarily mean the internal regulator is working properly. Voltage is but one indication of what the alternator output is---you need amperage to recharge the batteries.
J W has a good thought with parasitic draw, that's certainly possible. I think a bad alternator is very possible here as well. Many times alternators can fail in stages where they no longer can produce their rated current. If that's the case it may not be able to keep up with your electrical load until it sees higher RPMs.
Most auto parts stores can test an alternator while it's in the van. They hook some equipment to the battery and a couple of cables, and if I remember right they can determine the output of the alternator. I'd start there and see what they say.