I have a 525TDS which has done approx 130,000 miles and is approx 10 years old. (I believe this engine is also used in the 2.5 ltr diesel Range Rover )
It has become increasingly difficult to start on occasions, which seems time-related to when it was last run. About 3 months ago it was difficult to start in the mornings - more recently it was difficult to start at the end of the day and this week it is difficult to start after an hour of leaving it, when the engine is still warm.
I have fitted a new "lift pump" (on the tank) and fitted new glow plugs (old ones were OK though) - the pump runs for about 45 seconds on ignition switch-on and the glow plugs draw current for their time period when the engine is cold enough to demand glow-plug heating. The engine, once started, runs perfectly when cold or hot at idle and normal running speeds at all revs - fuel consumption is normal - the fuel filter on the bulkhead has been replaced recently.
I do see a large air bubble (about a foot long) appear very readily in the plastic tube from the filter to the injection pump. This is initially pushed towards the injector pump when the ignition is switched on and when the engine eventually starts, quite a bit more air is initially seen rushing along this pipe towards the injector pump, although after a few seconds this disappears as, I presume, diesel takes its place. Once the engine has started, it runs well immediately, cold or hot engine, cold or warm weather.
I feel sure that this air bubble is key to this problem but the main BMW dealer says "they all do that".... I really don't want to go too near the injector pump until I have exhausted every other possibility, but not sure what else I can check. There is no diesel leaking out of anywhere I can find ( no puddles under the car / smells) but somehow air seems to be leaking in.
Can anyone suggest any other areas for me to investigate or is this a classic symptom of something ?
Thanks,
Nick