Will the IRS keep an electronic payment (so it is on time) made with efile if they reject the tax return?

Yes, the payment will not be scheduled or paid if you paid through TurboTax and the return was rejected - the payment gets rejected too; the return is 'unfiled'.   If your return was rejected yesterday before the deadline, you can still e-file it and it will be considered on time.   

You have until April 23 to correct the rejection and refile your return to avoid possible penalties.  By midnight on April 23, your return must either be retransmitted (and later accepted, regardless of date) or postmarked for it to not be considered late.

If you owe taxes, must still pay by April 18.

Some returns keep getting rejected through no fault of the taxpayer; most commonly, this is incorrect data on the government's end, causing a mismatch and subsequent rejection.  If you're in this boat, file a paper return, as it can take weeks, even months, for the government to make the correction in their system.