I'm working on a 95 direct injection diesel that won't start without a small shot of either. Runs good after starting shows no codes. Tried a different computer,new fuel filter. What could be the problem?

Check the glow plugs. Be sure to replace the under frame and under hood fuel filters. Ensure the oil level is full and that it has been recently changed, along with the filter.

I have axcess to a snapon scanner and will test glow plugs but need to know how and where to test the high pressure oil pump. The scanner shows 170 psi at the sensor during cranking is this not enoughf to fire the injectors?