Xantidote wrote:One source of air into the fuel lines, as may have been mentioned in relation to your previous problem a while back, is the small diameter black return fuel lines to/from/between the injectors, including the sealed short end fitting at the nearside end of the cylinder head. Over time, with heat and age, the pipes (about 4 mm dia.) tend to harden.
Agreed - except I'd have said, "...
especially the sealed short end...".
These small pipes are usually referred to as "leak-off" pipes because they return fuel leakage past the needle valves inside the injectors back to the fuel pump where it joins the leakage from the pump to all go back to the tank. Because the whole fuel system under the bonnet is higher than the tank, and the lift pump is integral with the injection pump, all of it, apart from the high-pressure side between pump and injectors, is below atmospheric pressure and, because air is vastly less viscous than diesel, air is easily 'sucked' into the low-pressure system.
Over-night, the tiniest leak will allow the injection pump to partially drain back to the tank. Then when you try to start in the morning, the pump has to prime itself; however, as there will still be some fuel in the bottom of the pump, injection will start on two cylinders before the other two - hence the hesitant start.
From experience I'd suspect that you have BOTH an air leak AND a couple of duff glow-plugs.
Replace the leak-off pipes. Sometimes 'universal' kits don't include the blind end, make your own from a stub of new pipe sealed with a suitable plug. I used a S/S wood-screw, 1mm larger in diameter than the pipe bore, with a plain, tapered, length under the head. With the thread cut off, and the cut end carefully smoothed this is a tight push fit and can be re-used when the pipe goes hard. It's important that the plug be smooth to avoid the slightest air-leak.
Check the whole fuel feed under the bonnet, from priming bulb to filter to pump, for leaks. Bad leaks will show as a slight weep of diesel if you keep pumping with the priming bulb. Replace any suspect pipes. The priming bulb itself might be faulty as might the connection at the bulb with the pipe from the tank. BTW it's normal to have to keep squeezing the priming bulb because the pressure leaks away through the pump's internal leak-off. Check for leaks, particularly under connections, with bits of paper towel. Be very careful if you tighten the 'banjo' connector on the fuel feed into the pump, it's easy to distort the banjo making a slight leak worse and difficult to cure. This steel pipe is NFP! Guess how I know...
You can check the individual glow-plugs with a DVM, but while dead plugs will show up as open-circuit, plugs which don't glow right to the end and are thus not effective, may appear to be O.K. When removed, plugs like this will be sooty at the end. A good plug should have a resistance of around 1.2Ω (between body and threaded connector). Power cable must be disconnected from a plug to test it. The centre two plugs are easy to test in situ, the end two are a bit of a nightmare.
[EDIT]
Glow-plug Wiki here
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