Help!! Spill pipes problem (again!)

[Zanimat]

I thought I'd solved the problem of the leaking spill pipes on my E300D W124 (multivalve) but I was wrong! One or other of the pipes keeps blowing off the injector stub - with consequent flooding of the engine compartment with diesel!
The pipes are the correct MB part and it occurs to me that there may be too much back-pressure in the fuel return pipe to the tank? I have removed the check valve at the top of the pipe & that is completely clear - but I cannot blow down the pipe which goes to the tank. Should I be able to do so, or is there some other valve which only opens when the engine is running? I have tried using a small tyre compressor & that shoots up to 100 psi as soon as I push it onto the pipe. I can't hear any bubbling in the fuel tank.
The fault does seem to be speed related - if I waft about at 30~40 mph it all hangs together, but a high speed burst will blow a pipe off.
Can anyone help, please??

 

[wireman]

The return pipes should offer no restriction to flow, examine the return pipework for crushing and blockage or degraded rubber hoses.

A small tyrap may help prevent the blow off but you should in reality find the real fault.

 

[Zanimat]

Thanks, Wireman; yes, I had been thinking of fitting small clips on the pipes - but it really shouldn't be necessary; just covering up the problem, which will probably get worse! I ran the engine for a few minutes this morning, then stopped it & released the return pipe connection at the filter - diesel blew everywhere! So there is a build-up when the engine's running. I can't go rummaging around underneath cars at my age, but I have booked it in with the local garage for a spot of "un-plumbing" on Friday. Just hope they find a simple blockage at a union or something!