Engine cranks but wont start
 

I have been trying to resolve this problem for over a week, still no luck. I am new to diesels, so all i have done i read on line. I have changed the air and fuel filters, icp sensor, ipr valve.
I cleaned the fuel bowl and the pressure release valve on return line. also checked new fuel filter to make sure it released the check valve. also replaces cps. i can hear the fuel pump run and bowl has pressure, i don't have a gauge to check it. I put a scan gauge on it, and when cranking it has 168 rpm, 10.5 volts, 40 ipr and 1900-2300 icp? I have gotten it to start a few times, don't know why, when I try what I did to start it the next time it doesn't start.
also doesn't show any codes, and wts. light comes on. any suggestions would be greatly appreciated. Oh and glow plug relay is working, but I do think glow plugs are weak. had trouble starting in cold weather but started good with block heater. Also when the engine started it lopped at idle for a few seconds smoothed out and ran good. icp at 550 at idle.

Hpop issues .. sensor possibly , or the CPS could still be bad .. had manny new ones that were no good .. just in case I would replace again , just for good measure .

x2 hpop, you might want to check oil level, and or change oil if it hasnt been done for awhile.

May want to hook it to a scanner and get some live info on the engine stuff, Live is better than guessing ......

And yes, change oil - try Archoil AR9000... herd manny good things as far as the Ps engines... helps loosen all the crud from injectros and HPOP...