What temp and grade fuel?
Grade might be 1, 2, Arctic.

You can find a lot of data on fuels in the first section of the Military Handbook 1022A.  

Do a web search for MIL-HDBK-1022A and download the handbook.

If you can't find it, give the grade and temp and someone will be able to help.

You don't give what temperature but I'll assume it's close to ambient, say 100F to be conservative.  Here are two approaches.

Diesel comes off the sidedraw of a crude column with about 400F initial boiling point.  If you correct that to 100F (Nelson has a chart in their book), you'll get under 0.1 psia.

Another estimate is off the flash point.  Diesel has a flash point around 150F.  For most heavier HC, they have an LEL (which is what the flash point corresponds to) of about 1 to 1.5 mol%.  That works out to just under 0.2 psia at the flash temperature.  Correct it back to 100F and you have again less than 0.1 psia.  

In effect, unless you diesel is pretty hot, vapor pressure isn't a concern for NPSHA calcs.  

TD2K's VP estimate via flash point is -to my grasping- an excellent approach. There are, however, Diesel specs that alllow for lower flash points.

I can't take credit for the flash point method, someone else on the site posted it quite a while ago, I was quite impressed by the approach.