Couldn't get my 82 1.6 N/A pickup to start the other day, would crank for ages but wouldn't fire. Had my local mechanic adjust the timing, and it started up just fine, several times, for a day. Sat last night and now I'm having the EXACT same problem, not firing, spitting clouds of white smoke. What could be going on here?
first thing i'd get a test light on the glow plug bus bar and make sure they are getting 12v when the glow plug light is on. if you know you have working GPs then move on from there. could be a lot of things..
No compression, off time, or glow plugs. Could be any one of them. I would first check the glowplugs with a tester, or check if it is getting fuel.
Compression generally goes south over time, as does timing. If it all of a sudden was hard to start odds are glowplug system: fuse, relay, or plugs themselves. I just had 3 plugs drop dead within 48 hours of each other... I suppose it's like light bulbs... all come out of the same factory, should have the exact same lifespan.
Voltage to the buss is the first test, if it passes this then you need to measure current to the buss (48+ Amps when cold)... if it's dodgy you'll need to pull the buss bar so you can measure the resistance and current of each plug... judging on your symptoms is sounds like they are all gone... hope for the relay or fuse (the buss bar is a PITA as are some of the plugs themselves !).
Ok here's a dumb question then; where is the GP buss located?? :oops:
Just so I know in the future if I have this problem

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Ok here's a dumb question then; where is the GP buss located?? :oops:
It's that flat copper bar that connects all the glow plugs together.
i've pretty much fallen in love with the way the TDI gp's are connected... maybe i will take a pic sometime

hmmm... if your mechanic fixed it by timing it, have the timing re-checked... if it's off, then something is going on. maybe the IP is getting loose somehow...
sometimes poor starting could be air in the lines from a leak... low compression should be black smoke coming out of the tailpipe.