E34 525 TDS fuel /starting problems

[Nickhlx]

I have a 525TDS E34 1995, done 130,000 miles in generally good condition.
Recently it has been difficult to start and I have already done the following after reading threads on a newsgroup.
New fuel pump on tank, new glow plugs, replaced injector by-pass hoses,
pressure/vacuum checks on fuel lines, new fuel filter.
I notice that air seems to fill the transparent fuel line from the filter to the injector pump when the problem occurs, but the main dealer is adamant that is not a problem and "they all do it" - (I can't see how an engine is meant to start if its injecting air).
Sometimes the problem is gone for a day or two, sometimes it re-appears after an hour - to start it I have to turn on ignition for perhaps 20 seconds until the tank fuel pump times out maybe 3 or 4 times. There is no cloud of diesel smoke when it starts so I don't think an injector is sticking open and draining the fuel into a cylinder (I might be wrong). Oil level is not increasing !
There is slight moisture(diesel) weeping out of injector 4 (the master injector that senses TDC) but so slight I don't think any significant air could be leaking back in. The engine once started always runs just fine whether hot or cold at all engine speeds from idle to running speeds and returns normal fuel economy.
I am sure air is leaking in from somewhere but no diesel is apparently leaking out from anywhere.
Can anyone tell me any other points to check, else the garage wants to remove/test/replace the injectors and if that doesn't fix it to look at the injector pump, both of which will cost megabucks, and I am not sure yet that it isn't still a simple cracked pipe or hose or something simple ?
Thanks,
Nick

[BobHarris]

Check that the glow plug relay is actualy working with a multi meter.

Listen for it turning off, the light may go out prematurely (sp?) so you try to start before the glow plugs are hot. (have only seen this happen on Fords and Vauxhalls, but may still be relevant).

HTH

All the best

Bob

[Nickhlx]

[QUOTE=BobHarris]Check that the glow plug relay is actualy working with a multi meter.

Listen for it turning off, the light may go out prematurely (sp?) so you try to start before the glow plugs are hot. (have only seen this happen on Fords and Vauxhalls, but may still be relevant).

Hi Bob,
I am sure it is - the interior lights go dimmer when switching on, the glow plug light goes out after about 10 seconds and the interior light stays dimmer and brightens after about 20 seconds (not timed it) so I assume that is the plugs turning off - each glowplug takes some 17 amps times six is approx 100 amps total - quite a relay ! - do you know where it is ?

Nick

[BobHarris]

[QUOTE=Nickhlx]

Check that the glow plug relay is actualy working with a multi meter.

Listen for it turning off, the light may go out prematurely (sp?) so you try to start before the glow plugs are hot. (have only seen this happen on Fords and Vauxhalls, but may still be relevant).

Hi Bob,
I am sure it is - the interior lights go dimmer when switching on, the glow plug light goes out after about 10 seconds and the interior light stays dimmer and brightens after about 20 seconds (not timed it) so I assume that is the plugs turning off - each glowplug takes some 17 amps times six is approx 100 amps total - quite a relay ! - do you know where it is ?

Nick

Sorry, I don't know where it is, but you should be able to hear it click off.

HTH

All the best

Bob