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fuel pressure problems


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#1 Mark Adams

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Posted 10 October 2012 - 01:50 PM

After finding my freelander 1998 1.8 running a bit rough and missing, I decided to perform a fuel pressure check and found that the priming pressure was only 1.5bar which immediatly drops back to 0. When started the pressure only rises to 2.5bar (not 3.5) when idling and yet again drops to 0 when the engine is stopped.

I have taken out the fuel pump and replaced the fuel filter as I initially suspected the O ring, but it was fine. Put it all back together and it is still the same.

I have tried running the engine and then clamping the fuel line on the engine side of the gauge to see if the pressure leaks through the fuel rail/injectors or inside the pump and it still drops which indicates the problem being inside the pump.

I now suspect that the pressure regulator is at fault but would like to try and test it before just replacing it. Does anyone know a good way of testing these?

I am also wondering if I should just buy another pump rather than just the regulator.

Thank you

#2 FridgeFreezer

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Posted 10 October 2012 - 01:55 PM

I've got a spare pump (complete with tank) here (Gosport) if you want.

From memory there's a small link hose inside the pump that could be dodgy.
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#3 Mark Adams

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Posted 10 October 2012 - 02:00 PM

Thank you for the reply. Unfortunatly Gosport is a bit far from Wales to collect the pump. I do not need the tank but would be interested to know how much you would want for the pump if you can post it.

I did check the clear red/orange pipe which goes to the fuel outlet and it visually looks OK but not pressure tested it.


My e-mail address is: info@penrhiwfarm.co.uk if you prefer.

Mark

#4 Mark Adams

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Posted 17 October 2012 - 07:07 AM

Hi,

I decided to purchase a new fuel pump which I have now installed.

I connected the gauge back up to test that all was well and these are the finding.

When primed the pressure quickly rises to 3.5 bar but then drops to 3 bar and holds.

When the car is running it runs at 3.5 bar but when you open the thottle the needle shakes a little and then settles again when the engine is shut off the pressure drops to 3.0 bar and holds.

I would have expected it to hold at 3.5 bar not 3.0 and was not expecting the judder when opening the thottle.

Any ideas? Could the judder be caused by the Damper?

#5 FridgeFreezer

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Posted 17 October 2012 - 07:51 AM

Does the fuel pressure regulator have a vacuum pipe connected to it? If so it's probably maintaining 3.5bar across the injector relative to the vacuum on the other side, when you blip the throttle there is less vacuum so the pressure goes up - you are measuring relative to the surrounding atmosphere all the time.
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#6 Mark Adams

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Posted 17 October 2012 - 08:17 AM

Hi,

The pressure regulator on the Freelander 1 is inside the fuel pump so does not have a vacuum pipe connected.

The fuel rail does have an accumulator (damper) connected to it which has a vacuum pipe but this does not regulate the fuel in any way just smooths it out.

Hope this helps

Mark.

#7 Mark Adams

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Posted 17 October 2012 - 08:17 AM

Hi,

The pressure regulator on the Freelander 1 is inside the fuel pump so does not have a vacuum pipe connected.

The fuel rail does have an accumulator (damper) connected to it which has a vacuum pipe but this does not regulate the fuel in any way just smooths it out.

Hope this helps

Mark.




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