Ok read all the forums currently on 300tdi injector pump timing and head issues. I will list what has been done and tested!
Engine run fine before starting just pressurised via water instantly.
I have replaced head( new bolts,gasket and injector copper washers.)
While doing head also decided to change timing belt to make sure this was new as no service history.
I replaced with the new tensioner and the moded bottom crank pulley to solve belt slip. I did mark off the crank a TDC along with the Cam and locked IP with bolt in hole!
Checked all valve clearance on rocker covers and attempted to start but failed. Checked lift pump this was not priming by hand so replaced with new one. Primed system filter to remove air, then lossened union at injector end. Diesel does spray but not under as much pressure as expected when turning over. Have checked solonoid on IP this is fine.
Engine will fire up using a snif test ( Easy Start) but will not run on diesel.

I have checked IP timming again to ensure its ok and seem almost impossible to get this wrong if all TDC and pump locked off?

Any idea's its driving me nuts! PS have had the head tested to make sure it was not valve seats releasing pressure? so compression is fine also?

are crank mark cam mark and pump pin all aligned

James I had the head off when set up so could see psitons 4 and 1 at top and yes crank pulley at 12oclock, Cam lined up with case mark and pump locked off. I even used white paint marks to make sure nothing moved. only movement I had was in the refit of belt when backed of the 3 pump bolts. This should not affect timing though as pump pin lined up. I have removed and checked this twice just incase?

3 bolts allow you to get belt and pump spot on so as long as the 2 marks line up and pin should be okay,pipes on lift pump okay ,injector pipes in right order though you shouldnt be able to get them wrong ,if you slacken front banjo bolt is there much diesel coming out when engine cranked ,tappets 8 thou no 9 method

When I crank the engine with front banjo bolt loose there is a spray of diesel but its not under as much pressure as id expect. Normally good injection would shoot diesel quite high this just squirts out an inch or so?

UPDATE! After getting the replacement head checked to ensure this was not the issue I have now got it running. Head was fine with not issues.
On rebuild while head off decided to check timing belt again. Locked pump off with pin and noticed that 4 and 1 piston were around 4mm off top of bores.
So loosened the 3 pump bolts lined up pistons at top and ensured all timing marks lined up. replaced belt. The only difference in tightening sequence of setting timing belt was to leave the 3 bolts loose on pump while you tension the belt and the lock these bolts off. I only see that if anything the timing may of been out a couple of notches so not convinced this was the issue but hey it runs! )