Disco 1 Diesel pump question

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gR@HaM

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The electric buzzing sound of a 300TDI diesel pump should this be constant when the engine is running? I ask because sometimes it's not on my '95 disco. With ignition on and engine not running the sound is constant, with engine running sometimes the buzzing is intermittent.
I currently have an issue with the engine occasionally hesitating and in some cases completely bogging down, have removed both the diesel sedimenter and filter and cleaned them out. Was initially thinking the issue could be due to air getting into the fuel, but the injector leak pipes look ok and so does the drain back to the fuel pump. These are also clear pipes and I can see some bubbles coming out of the top of the injectors.
But my main concern is the electrics on the fuel pump, anyone know whether this is normal? If not I'm thinking it could be an expensive fix.
Shall upload videos of the buzzing without vs with engine running..
Thanks
 
Bubbles mean air, so you need to get rid of that ASAP. The air won't be helping the EDC FIP - and running a pump dry is often a bad idea. Your EDC pump may be knackered, and it may be fine. I've heard noisy ones and quiet ones. Get rid of the air and it'll probably be a whole lot quieter. Search on here for ideas as to where to look, but it'll be worth looking at the feed and return from the tank - they rot, as does the sedimenter.....
 
Is it an auto with EDC? They make that sound. If it hesitates some times it may be the throtle position sensor.
 
Usually lack of fuel at top of quantity servo causes the buzzing sound. There should be NO air bubbles at all in the feed lines.
 
So there should be no large air bubbles visible in the injector overflow pipes?
Thanks

Yes, there should be no air in the system... The Bosch pumps are very tolerant of air, and this is almost a problem as when the cliff edge of intolerance is reached, it comes as a shock.

Usually lack of fuel at top of quantity servo causes the buzzing sound. There should be NO air bubbles at all in the feed lines.

Agreed. The servo will be "buzzing" all the time, but the diesel will dampen the noise significantly, making it just about audible. the sound being variable and air in the spill pipes potentially sounds like two facets of the same problem to me.

If the EDC pump is kaput - there are plenty on ebay for not much money - they are of course an unknown quantity, but they are out there. I took EDC off my auto D1, so thats possible too... I still have the pump if you are desperate.....
 
Yes, there should be no air in the system... The Bosch pumps are very tolerant of air, and this is almost a problem as when the cliff edge of intolerance is reached, it comes as a shock.



Agreed. The servo will be "buzzing" all the time, but the diesel will dampen the noise significantly, making it just about audible. the sound being variable and air in the spill pipes potentially sounds like two facets of the same problem to me.

If the EDC pump is kaput - there are plenty on ebay for not much money - they are of course an unknown quantity, but they are out there. I took EDC off my auto D1, so thats possible too... I still have the pump if you are desperate.....

The pump and lines should be full of neat fuel at all times, excess internal pressure is returned to the inlet side of the injection pump through the relief valve. Fuel also being returned to the tank via the bleed off hole in the spill return connection. There should be no air in the spill pipes or any other pipes at any time. Any air that does get in to the system should bleed off through the spill return. Obviously in this case a lot of air is being drawn into the the feed lines either by the lift pump in which case the leak will be aft of that or if the lift pump is duff by the injection pump when the leak could be anywhere between the injection pump and tank.
 
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