My new oven has 4 wires and my old oven had 4 wires but my home service only has 3. I found that the old oven had the white wire connected to the ground should i do the same hook up?
If I am reading this right, by "home service" you mean your range receptacle has three prongs, and three wires with no ground wire supplying the receptacle.
If that's the case, you'll want to connect the bonding jumper from neutral to frame ground in the range:
If that isn't the case - if you have a ground wire / ground prong on the receptacle - you do NOT want that jumper strap connected!
That picture is from this article:
Your service wires overhead, the 3 wires I assume you're talking about do not contain the " grounding conductor or earth ground. In your panel or first disconnecting means,the grounding conductor goes to the ground rod or in some older homes to the water pipe .If this occurs at a disconnect ,then in your panel the neutral and ground are seperate. The key words are grounded and grounding. But from the panel to a 240 volt outlet you will have 4 wires to complete the ground fault or short as some might say. This should help you understand why you see 4 wires at the outlet.Also check for a conductor at your water heater strapped to both cold and hot water pipes if they are copper