Common rail pressure

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Darrnw

New Member
Posts
82
Does anyone know what fuel pressure is needed at the common rail to start the engine? My car is 1023 kpa before turning the engine over. Does that sound enough?
 
This reading is probably residual pressure - as the high side pump is mechanically driven from the engine,you wont get a proper reading.Also,Testbook tends to crash when you crank the engine.
Do you have a no start issue ? After you have checked that the low side fuel delivery pressure is ok the next step is to check for leakback through the injectors.remove the spill pipes from the top of the 4 injectors and clamp off the pipe before the first injector coupling.Now switch on the ignition and look into the open tops of the injectors,if any of them have fuel rising up in them this is why it wont start.You will need to replace that injector.
 
What a **** ! just read all the other posts about your non start issue,now I've read that lot,I've got £20 on you having a leaky injector.Testbook will not help with this fault because its outside of what it can observe.The bit about tow starting it confirmed my suspicions,the higher cranking speed meant the high pressure pump was able to deliver enough fuel to support combustion - I bet it ran ok too.Switch it off though and immediately try to restart and it wont go.
How much are you going to charge your local independant for the diagnosis ?
 
I've clamped off the fuel return, disconnected from all the injectors dried the tops of the injectors and turned the engine over they are still dry as a bone so I would rule the injectors out unless you have any other thoughts?
 
Should have made it more clear,DO NOT crank the engine,just switch the ignition on and watch for fuel rising up.
 
No still not sorted! Got a guy coming around in half an hour for a second opinion! Will let you know his verdict!
 
The LR bloke has been over,plugged the machine in to the car no errors, he did notice that on position 2 the common rail pressure was way low! He suggested the pump under the bonnet or the high pressure pump crank driven and very kindly lent me one of the wing mounted ones to try! It was not that! But as I said to him the HP pump on the crank shouldn't have anything to do with the pressure at the rail on position 2 as the engine isn't being cranked! To which he agreed and has gone off to have a think about it!

Any ideas?
 
Have you tried the leak- off check without cranking the engine yet ? By the symptoms I still think that is your problem.It wont gush fuel up out off the faulty injector it will just steadily rise.If you do find one that the fuel rises up in just put it all back together again and clamp the hose tight to each side of the faulty injector,then try starting it.If it fires up then that confirms it.
 
If there is no fuel rising in the leak off's then I'm afraid the chances are your high pressure pump is not capable of delivering a high enough pressure to give a decent start quantity.If all the live data is ok reguarding low and High side fuel pressure whilst the engine is running then you need to find a fuel shop that is able to bench test and recondition the high pressure pump.This is not cheap.Nor is a new pump,might be worth doing a net search on parts finder.
Good luck.
 
The bloke who came out the other day said that the pressure at the common rail before cranking was way too low. He suggested a pump problem, he very kindly lent me 2 pumps one lift pump(under the back seat fits in the tank) and the front pump(in a carrier on the inner wing next to the recently changed fuel filter) As the problem is before cranking and the high pressure pump is a mechanical cam chain driven contraption I would pretty much say that is ruled out!
So my way of thinking is that the problem lies between the front fuel pump and the rail! Any ideas now?
 
The only thing you can do now is to tee in a fuel pressure gauge between the low and high pressure pumps to check the actual delivery pressure to the high side pump.I still think you have a high side fault,(low rail pressure)as the engine can be tow started or smacked with easy start.(please dont do this too much - its not kind to the engine)
 
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