ABS pinhole in Tee.

There is a pinhole spraying water in my pressurized jet pump system where the heat cable goes into the line to the lake at the ABS TEE How can I seal the leak? If I depressurize the system, clean the leak area and apply ABS cement will this fix it?

After depressurizing, I would rough up as much of the area as possible with something sharp and emery cloth.
Then, plan on laying on globs of ABS cement. Letting it set up hard and lay on more layers.
It is important to let it set up because if it is too thick, the final layer will set, but the underlying layers will stay soft, as though it were still in a can.
Keep an eye on this joint for a few months to make sure it worked.

Didn't think ABS was used for continuous pressure applications.
But in any case, I would consider a patch using solvent welding (cement) a temporary fix and as advised by breplum, keep an eye on it.

Thanks. Am I correct in using a few thin layers of ABS solvent /cement rather than thick layers. How long in between layers? Should I use a hair dryer to speed curing?

Not that I have any first hand experience with this, multiple thin layers make a lot of sense to allow faster drying time. Although the main ingredient is likely the solvent, solids are included that are likely ABS materials, which should act as the patching material in addition to the first coat(s) that should help weld the pipe material at the pin hole somewhat. It makes sense but does, I believe, rely highly on the first coats adhession to the pipe.