Disco keeps cutting out and in and out and in.........

We have a problem with a 1996 'N' reg diesel Disco. We have recently had the fuel stop solenoid replaced due to the car cutting out or not wanting to start at various times. This appears to have solved this particular problem, but just over a week later another has reared its ugly head.
At 2,500 to 2,600 r.p.m. the engine cuts out, if you dip the clutch the needle plumets, but as soon as it hits 1,250 r.p.m. the engine cuts back in. The car starts and stops as it should, but if you sit in it and push the throttle right down it cuts out at the 2,500 mark then back in at 1,250 cuts out as it reaches 2,500 back in at 1,250 etc etc.
The car is perfectly driveable and doesn't miss a beat as long as the revs stay below 2,500 at which point the above happens.
Has anybody got any clever ideas or has this happened to you and what was the cure?
Thanks in anticipation

Andy L. (if at first you don't succeed try a bigger hammer!)

you could have a piece of **** in your fuel tank that draws onto the end of the pick up pipe under pressure, it could aso be a dirty fuel filter or even a bit of **** in the injector pump

is the fuel line kinked anywhere or partially blocked by a rubber hose degrading?
try running the engine from a different diesel supply, ie a gallon fuel can, independant from the vehicle fuel tank,shouldnt be difficult to arrange with a few lengths of fuel hose, supply and return.
is the injector pump mechanical or electronic?

As far as I can make out the pump is mechanical taking its drive from the belt assembly on the front of the engine that drives the alternator, power steering pump etc. I don't think it's dirt anywhere, but will check tank, filter etc. It seems to be too consistent to be an intermittent blockage. It's like a switch being turned off and on repeatedly. If anyone is familliar with speed restrictors on lorries, it's almost like one of those set really badly.

Andy L. (if at first you don't succeed try a bigger hammer!)

sounds like the fuel filter to me

Andy Light said:

As far as I can make out the pump is mechanical taking its drive from the belt assembly on the front of the engine that drives the alternator, power steering pump etc. I don't think it's dirt anywhere, but will check tank, filter etc. It seems to be too consistent to be an intermittent blockage. It's like a switch being turned off and on repeatedly. If anyone is familliar with speed restrictors on lorries, it's almost like one of those set really badly.

Andy L. (if at first you don't succeed try a bigger hammer!)

Click to expand...

are you talking about the injector pump here? or the lift pump
there are two pumps on tdi enjuns
lift pump is at the side of the enjun just under the fuel filter but forward a bit.
don't know if thats any help to you but diaphrams on them do sometimes fail
might be talkin out me arse but oh well

Thanks all for the suggestions. Got totally ****ed off with it and left it where it broke down last week. Went back to it Thursday with jump leads having killed the battery and it went first time. It appears to have lost its last problem, you can now rev as high as you like and it's fine. However, when it gets warm now it cuts out and won't go again until it has cooled down good and propper. By warm I mean reached normal operating temperature. We've given up and booked it into a garage to be looked at. Luckilly the garage are closed until Wednesday cause it only goes a couple of miles before it gets warm and dies. By Tuesday night we should get it to within spitting distance so there is only the last sprint to do Wednesday morning.
I'll let you know what the outcome is in due course.

Andy L. (forget the big hammer, has anyone got a match?)

This is the cause of a similar (and thankfully infrequent) problem on my Disco after everything gets hot, apparently it's quite a common fault:
There is a little black box behind the heater controls under the radio, it controls the central locking and the immobiliser.
They are prone to getting a 'dry' soldered joint which only rears it's head when the unit gets hot, this prevents the Disco from starting.
The problem is made worse by the fact that there is a lot of heat radiated from the heater unit and the hoses leading to the vents which surround the unit.
Normally takes about 20 mins for it all to cool down and it starts fine.
Maybe you have the same problem but worse??