[wibble]

iv a '97 mk2 diesel mondeo which has done 152'000 trouble free miles but this last week has not been starting 1st time as usual. it doesnt matter if the engine is hot or cold it's being a nightmare to start to the point where on a couple of ocassions flattening the battery .
iv changed the glow plugs which has made no difference , the relay is workin so i am at a loss of what's wrong and really would appreciate any help in pointing me to the probable cause

[wibble]

forgot to say it's an 1800 turbo diesel

[Hometune]

In the fuel pipe between the fuel filter and the pump - the one that loops up - there is a non return valve (It is part of the pipe and costs around £18 from Ford). Check this is working okay by disconnecting at the pump end, then press the fuel primer on top of the filter a few times. If fuel comes out easily it is okay.
The other fault could be an air leak allowing fuel to return all the way back to the tank. So, next time BEFORE starting, pump up the primer a few times until resistance is felt, then try starting. This will eliminate this possible fault.
If you have used bio-diesel, cooking oil or other fuels, drain them off and fill with proper quality diesel and add a diesel cleaner to the fuel tank.
When you say the relay is working, I take it you mean the fuel shut off solenoid. Have you removed it, removed the spring and plunger and refitted it then tried? A click may not mean its opening far enough. You will have to stall the engine to stop it after you get it started. Handbrake fully on, foot hard on footbrake, let clutch up steadily with car in gear until it stalls.