Thank you for your help question, my name is ***** ***** I am a fully qualified technician with over 30 years in the trade. Hopefully I can help you.
There should not be a great deal of pressure in the leak off system and providing there isn't a blockage in one of the pipes I would suspect that the problem is a faulty injector allowing the high pressure to escape via the leak off pipe.
This would explain why the pipe keeps blowing off.
The test to do is called a leak off test, and your garage should know how to do this but i will briefly explain.
You first need to disconnect all the leak off pipes from the injectors and block the return pipe to prevent any fuel running back.
Then a short length of pipe needs to be attached to each leak off outlet and then placed in a container, so you will need 4 pipes and containers for a 4 cylinder engine all the containers should be same size, there are dedicated kits available for this test.
now the engine should cranked for around a minute, it mat start but that is not a problem, after this time stop cranking or switch the engine off.
there should be a few mm's of fuel in each container, if one or two have a greater quantity, this shows that the injector is faulty.
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