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Do you a lot of grey or white smoke after the engine has started?
Yes, Big time
its quite embarrasing realy
Ok, that rules out a fuel problem, as the smoke is unburned fuel from trying to start the engine.
You have measured the resistance accross the glow plugs, but the next thing to do is to take them out, and power them up with a set of jump leads, make sure each one glows almost instantly bright red, disgard them if they dont and replace them, this is most likely your problem.
If they glow, then reconnect them to the wiring on the car, earth them against the engine or with a jump lead, and make sure they glow when the ignition is switched on, even though you have battery voltage at the plugs, you may not have the ampage to power them fully, if they dont glow, then you need to check the wiring between the glowplug relay and the plugs, and the relay and the battey/fuse for faulys or bad joints.
If the glow plugs are working fine, then check the compression of the engine using a compression tester, you should have between 20-23 bar compression in each, this can be measured through the glow plug holes rather than removing the injectors.
If the compression is good, and the glow plugs are fine, then it would point to an injector fault, it may be that they are not injecting very good, but, usually in these cases, the car smokes when running normally.
Hope this helps, if you need more assistance, please let me know.
Ok, will check the glow plugs but
how do i check the compression. is that a garage job?
i am an electrician (household) i know the basics because i have been running about 4 vans for 7+ years.
Every winter i have starting problems with vans, but usally the easy jobs - battery, glow plugs i now do my self because they are common and easy.
but i am no mechanic.
The compression test is easy and only takes a few minutes once the glow plugs are out, you screw a special guage into the glow plug hole, crank the engine over, and read the compression from the guage.
You can get diesel compression test guages from tool shops, or there are cheap ones on ebay for about £90.
I'm pretty sure you will find a glow plug problem though, so check this thoroughly first.
Ok will check the glow plugs this afternoon
Let me know how you get on, and if you need further assistance.