Just replaced the PTO pump on our GU813 and every time we try and turn on the PTO the truck chuts down. We have had this problem in the past and I replaced one of the PTO relays in the dash and that fixed the problem. We didn't disturb anything electrical on the PTO system when we replaced the pumps, other than remove the batteries. The PTO is hydraulicaly engaged with a pressure switch on the valve. In case it matters the pumps are being used to run a national crane 500E2. But I'm pretty sure the problem is with the truck. any help is appriciated. And electrical schematics would help alot. thanks.