Well it should not hurt anything. Make sure to notify the shop that fixed the pump. Just so they cannot later claim it is a new fault or whatever.

I was just sittting here thinking that if the problem does not go away. Try the engine on vegatable oil. If the engine remains firing on the number five when hot. The element bore is bad.

If not probably the element piston is sticking. I was also thinking about some aditive that might help the piston and bore if it is sticking but cannot think of anything.

Using the engine and pump may yet kind of lap it free with some time if it is a little rusty.