Hey guys I bought a 2008 transporter 6 months ago now has 190,000 km and I have just changed the camshaft, followers, oil and filter because it was backfiring and put scrapes in the camshaft and followers were rounded a little,
Typical car dealer bodging up cars...
Anyway I can’t afford to take to Volkswagen to find the problem and need it for work

It turns over but won’t fire, it was running before we pulled it apart,
also the battery went flat during the time waiting for parts, my dad is pretty confident the timing is right (being a diesel mechanic)
After about 5 seconds of turning over the oil pressure light comes on and beeps

Any help would be greatly appreciated since we are lost for ideas
Thanks in advance, John