is it possible for a reciprocating pump to have back flow to suction side

yes

Yes.

_{Go on. Next question.}

In principle, no. The discharge valve will close and prevent this.

The discharge valve will close and prevent this.
Not if it's not worn, jammed etc.
The Q said 'possible' I believe?
Effectively most pumps are only as good as a pair of non-return valves in terms of stopping backflow.
Del

Agreed, but the answer did say "In principle", and that is what the valves are for.

Yes, but normally very little. If you have massive backflow, something has failed.

Please see: http://www.driedger.ca/ce2_pdp/CE2_PDP.html for a detailed explanation.

Here is a portion of the article:

There is a great variety of positive displacement pumps. They are divided into two broad categories: Rotary and reciprocating. From the controls point of view, however, they are all similar. Their characteristic curve is so simple that it is rarely drawn. It is essentially a straight vertical line, as shown in Figure 2-2. (For some reason PD pump curves are usually shown with the pressure and flow axis exchanged. I will not follow that convention in this article.) All are constant flow machines whose pressure rises to whatever value is necessary to put out the flow appropriate to the pump speed. If the discharge is blocked, the pressure will rise until something yields -- preferably a relief valve. Close examination of the curve shows a slight counter clockwise rotation. This is due to internal leakage.

For positive displacement pumps the major cause of leakage is the small amount of reverse flow that occurs before a check valve closes and possibly past the check valve after it is closed. Leakage past the piston is negligible. Diaphragm operated PD pumps have no cylinder to leak past. Rotating PD pumps, such as gear pumps or progressing cavity pumps have internal clearances which permit a small reverse flow, called "slip" or "blowby". There is another reason why the curve may rotate to slightly lower flows at higher discharge pressures: The driver may slow down as the load increases. None of these have a significant affect in curving the slope of the characteristic enough that this slope can be used for control. For most practical purposes the slope is vertical. The system curve of the process is also shown on Figure 2-2. Its intersection with the pump characteristic defines the operating point.

As always, the process controls engineer has the responsibility of matching the capacity of a specific piece of equipment to the demands of the process at every instant in time. Rarely does the actual system curve fall exactly on the one used for design and selection. As with any two port device, there are three locations in which a control valve can be placed: On the discharge, on the suction, and as a recycle valve.

Contrary to a centrifugal pump, this is a positive displacement pump and will either move the rated flow or increase the pressure until something breaks.