Alright I got a 1998 New Beetle with a 1.9 non turbo diesel believe me ita a turd to drive but I'm not familiar with VW diesels and what all in them but here is the problem it will not start SOMETIMES unless you give it some ether or WD 40 also the glow plugs will randomly kick on and cause it to back fire and I discovered this and disconnected them before anymore damage was causes but does anyone have any ideas what could causes these I have changed the glow plugs and I messed with VWs before and pulled my hair out the whole time so any suggestions

 

The glow plugs have to glow after ignition. But this is outside temperature depended.
Check:
- fuel filter
- hoses (sounds to me like an air leak and these vw are really bitchy when they get air in the fuel intake)
How much torque did you apply to the glow plugs. Everything more than 15Nm will close the ring gap and cause a short and the plug is ruined.

The 1.9 SDI 's are known here as very reliable. Don't use the ether or WD40- it causes a lot of wear. Washes down the oil from the liners. Wear is like 6000miles driving just for one start.

 

I torqued it all right and the customer said she changed the fuel filter three months ago but after checking it for flow it was trashed so I got a new one and started up everytime so far I'll let ya know if it has more problems.