[Vwdiesel] Baffling Mystery...

[madmedix]

Hi Folks: 

Driving with the kids a couple of days ago, toodling down the street (constant speed)
when suddenly something went "WHAP" on the floorpan right under my
daughter's feet on the passenger rear area. Hmmm. Maybe a chunk of
debris or something. No problem, onward we go. 
The next morning...she will not start. Wants to, but won't. It has never behaved like this in its life (she has 507,000km on her; 26K on the timing belt). So I went through the usual suspects: 
- Glow bus is getting good power (plugs circuit pimped with the Ford relay and indicator light on the bus bar.) 
- Fuel cutoff solenoid ok 
- Fuel is getting into the IP (clear fuel line from filter to the IP)
- Battery is very strong and cranking well
(1050 CCA)
- I can smell the diesel-that-is-trying-really-hard-to-be-exhaust-gases after about 5 seconds of cranking. 

I'm thinking: Crap. Something fell off the car! That's what hit the floorpan. But what? It's not possible to
go back and see (freeway) and I can't see anything obviously missing.
No leaks. Weird stuff. All the IP bolts are there (cuz I'm thinking the
wants-to-start behaviour means she's out of time...jumped a tooth and
the object hitting the floorpan was coincidence? But the engine never
missed a beat. Nothing.) How would she jump a tooth if she was running at constant speed (about 2300 RPM, 3rd gear)? Wouldn't she have smacked in a valve or four by jumping?
I thought she may have lost "prime" overnight but I can suckle fuel easily with a bulb syringe. Help......

Cheers,
Andy