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Ask Greg Szczygiel Your Own Question
Greg Szczygiel
Greg Szczygiel, UK Car Mechanic
Category: Car
Satisfied Customers: 12
Experience:  Vehicle technician and electrician currently working in reputable independent garage in UK. Fully acredited ATA diagnostic technician.
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I have a Renault master van 62plate. It wont go above 50mph

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I have a Renault master van 62plate. It wont go above 50mph and is displaying the "injection fault" warning light. It has been scanned and has come up with the codes DF771 and DF025.
Where do I go from here?
Hello and welcome to Just Answer,my name is ***** ***** I'm looking forward to find the answer to your question.
I wouldn't worry about DF025 at this point, this fault code may bring warning message or engine light but will not make your car slow.
DF771 is the problem with diesel high pressure regulation.
Loss or unexpected diesel pressure.
Van won't go above 50 mph because the engine enters protection mode (limp mode)
There is a number of possible elements within high pressure diesel control which can cause this condition.
Where to go from here ?
You have replaced diesel filter already, so next thing to do would be injector test.
This can be done on the car if injectors are of solenoid type, using leak back test to establish portion of diesel returned by each injector.
If the injectors are of piezo type you should give your van to your local diesel specialist as they can only be tested on the machine.
If the injectors are all fine, high pressure pump and regulators must be checked, this can only be done when removed and tested by diesel professional.
There could be fuel contamination, faulty rail pressure sensor or bad electrical connection.
I'm happy to assist you further if required.
Customer: replied 3 years ago.

Many thanks. So how can you tell which type of injectors?

On solenoid type, leak off pipe is located on the top in the center of the injector (Bosch), if it is piezo the leak off pipes are on the side of the injector's housing or attached to short union.
On you van, you may have to remove air filter and the cover underneath to see the tops of injectors.
I hope it helps.
Customer: replied 3 years ago.

Thanks Greg. Mine are the solenoid type. If a leak-off test proves they need replacing, will they need coding? If they do need coding, what issues can arise if they are not?

I am sure this is my last question. Thanks

Yes they will need coding in, if they are not the following issues may become a problems.
Difficulty starting, incorrect fuelling on idle or full load, injector knock and other implications which you don't need.
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