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No get up and go Disco 300 TDi non EDC


spud murphy
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Hi all

Have spent most the week fitting and testing taking off and retesting prior to refitting the following after a sudden loss of all get up and go on a 95 300 TDI ES Auto with 69 on the clock that is now unwilling to rev beyond 2K and has all the get up and go of a warm letteuce.

Suspecting air in fuel system:

New sender unit fitted, originals unions were of a puff pastry appearance.

New fuel lines after they refused to be removed from the sedimenter and sender unit. Sedimenter bypassed after it also refused to play nice.

New fuel filter and lift pump.

All lines checked for both pressure and vacuum retention to 1BAR for 1hour each, no leaks.

System primed and starts on the button but will hover and chug around 2K RPM for 20 secs and then top out at 3K.

Induction side all present and correct, wastegate moving and turbo a blowing.

Exhaust was dropped from the downpipe after some one suggested maybe the cat was choked and acting as an engine brake.

Having replaced the entire fuel delivery system upto and including the fuel filter the disco is still starting on the button but laboring around the 2K mark for 20 seconds and then topping out at 3K.

Not convinced about the lack of air and hoping it's not the injector pump I decided to by pass the tank and run the engine from a 2litre clear plastic bottle sat on the inner wing by the brake servo.

So clear silicon hose to the lift pump from the bottle and clear silicon hose from the fuel return to the bottle ie closed loop.

System bled and engine started as normal. After 30 or so seconds the previously see through greenie/yellow diesel has gone opaque ie milky looking and there is bloody air in the fuel feed line!

It looks as though the disco is returning aeriated fuel back to the tank and my bottle is simulating the plastic well in the fuel tank that the sender unit sits in although the gauge is showing half full the fuel out and in lines are pretty close together down in there.

When the engine is turned off the diesel in the bottle becomes see through again after less than a minute and there are air bubbles trapped in the fuel feed line???

When looking at the spill return pipes they looked a bit tatty and a prime candidate for leaks seeing as they join back at the fuel return union. Replaced them all back to the union and no difference.

However I have noticed that if I pinch the silicon hose returning to my 2 litre plastic bottle 'tank' and then release the hose the small trickle of almost invisable bubbles in the returning fuel is transformed into a frothy surge

This can be repeated again and again so I think the finger is pointing at the injection pump??

Anyone have any knowledge of the Bosch pump, non EDC model??. Any known leak points??

Apart from all the diesel that has been sprayed and spilt around the engine over the last week there doesn't seem to be any fuel leaks from the pump itself.

Anyone got one knocking about they want to part with?

This is getting desperate now, cheers for any replies

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Can thhe lift pump release crankcase pressure into the fuel if the diaphragm is perforated? I haven't got one handy to look at till tomorrow, just thinking aloud :unsure: though you say you have changed that once already?

otherwise I would have said pinholed fuel line but you have done that....

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Cheers BM

I've now bypassed completely any original fuel delivery components and am now feeding the lift pump (which is new) directly from my clear 2liter bottle.

From the lift pump direct to the injection pump, from the pump back to the bottle.

System primes and engine starts, then there is a steady stream of minute bubbles returned to the bottle. This I think is simulating the antisurge well in the fuel tank where the original fuel sender sits, i.e Im taking from and returning to the tank a steady stream of aeriated fuel, engine just as lumpy and unwilling to rev past the 2K mark with my tempory 'tank' as it was with the main tank in line.

Anyone had their injection pump rebuilt??, any good experiances out there??

Any replies very much appreciated, thanks John

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I think you've done everything anybody else will come up with. I see a lot of 300Tdis at work and I've never heard of any such fault but if there is nothing else left in the system then it must be the injector pump I guess. Can't get my head around how, but it can't be much else.

I happen to know that Bearmach have got a special offer on injector pumps for June so it may be worth ringing them to see what the price to you is - the price I have seen is a hell of a lot less than a genuine one!

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The bubbles you are getting are classic syptoms of a perforated boost diaphragn on a TD engine. I've not heard of it on a Disco though. The bubbles would prevent the turbo from working and would pressurise the fuel tank if that's where they are coming from.

Les.

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Cheers guys keep 'em coming

I ran the engine with the boost pipe disconected and the fuel spill lines clamped back to the pump, but am still geting a stream of bubbles back to the bottle and if I pinch the return line from the pump you can feel pressure building and when released a frothy surge of diesel is shot back to the bottle.

Don't know the layout of the pump but was wondering if it's drawing air from one of the joints, no fuel leaking out though!

Cheers John

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The bubbles you are getting are classic syptoms of a perforated boost diaphragn on a TD engine. I've not heard of it on a Disco though. The bubbles would prevent the turbo from working and would pressurise the fuel tank if that's where they are coming from.

Les.

The Tdi pumps have a breather under the diaphragm to release air to atmosphere so unless there is a hell of a lot going through, it shouldn't be able to pressurise to any great degree - must be a different design to the TD perhaps?

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Cheers guys, I'll try in the morning.

This breather if I understand should let the air out after the diaphragm moves down under influence of the boost pipe presure???

When boost level drops the disphragm moves up?

Is this breather one way, does it have a check valve to prevent air entering.

The diaphragm pushes down I'm guessing on a fuel valve, needle?, is this isolated from the fuel path?

Cheers guys

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Just looking at alternatives

Does it rev better if the intercooler to inlet manifold boost-pipe is removed?

Symptoms seem similar to an internally collapsed boost pipe.

Or is the EGR still connected? If so, it could be stuck open, causing boost to be lost via EGR.

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I can't see that you have checked the pipe from the turbo to the injector pump. We had one with a fracture at the pump end the other day, hard to see but it made all the difference. Just an idea as you seemed to have checked just about everything else.

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Cheers Im and Jim

I ran without the intercooler hose fitted and it still chugs and hesitates at the the 2K mark, egr completely removed and blanked and the larger 1 piece hose fitted between intercooler and inlet.

When the engine is chugging at 2K I removed the boost hose connection and pinched between my fingers the now open banjo connection and can feel pressure build and air whistle out of it.

Still at a loss does anyone have any diagrams or internet links re the Bosch r509 pump?

Cheers

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You need to leave the boost pipe connected to the inj pump and do that test. It's supposed to have air pressure in it from the turbo. You need to determine if the inj pump boost diaphragm is sucking in air. Leave the pipe connected to the inj pump and blank off/clamp it nearby and see if that makes any difference.

Les.

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Cheers chaps

Les if I understand the underside of the diaphragm is not under any from of pressure/ vacuum, as there is the breather directly underneath to atmosphere?.

If it was split it wouldn't move?, but from diagrams there is a spring and offset cone affair that the fuel reg needle rides against as demand is placed on the pump??

There's no direct fuel pathway under there is there?

Western, if the wastgate actuator was split wouldn't this stop the dump valve opening as the system reaches 1bar and above?

Don't think it can blow that hard at the mo with it stuttering at 2K

Cheers John

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