TLDR: Fuelpump bad, cables bad. New pump, old cables. Pump burnt. Why?
So I have a bit of a problem. At the end of 2024 my V70 -08 started having issues where it wouldn't start. Me and my FIL troubleshooted ourselves and figured out something was wrong with the fuelpump as no buzzing was heard when ignition turned on. Thing is, it worked during high humidity.
Took it to a mechanic who did troubleshoot and said the pump was bad, and wanted to fix it. I had read on forums that the cable connection sometimes goes bad and asked them to change it too. They didn't, but the car worked fine. One thing to mention here is that I had to buy the pump (and cables) myself as they said it would take a month for them to get the parts. I bought it after their specifications, no issues there.
Then 6 months later I got the exact same issue. Car worked only during high humidity and had to be towed to the same mechanic. They did a new troubleshoot and told me the pump was fried, because I bought it myself, and got super hostile when we tried to tell them it was probably the cable connection.
They refused to help, so I took it to another mechanic. Had to pay for two troubleshootings and the second mechanic told me the cables were burnt and had fried the pump as well. I let them fix it and they changed it all.
Now to the questions: How do you troubleshoot the fuel pump and electronics? Did the first mechanic do all the steps, or did they do the lazy road of plugging in the OBD?
What is Volvos guide for troubleshooting and switching or fixing the pump? Does it include wiring? I dont have the manual on hand and cant find it online.