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Better acceleration with full fuel tank! Why?
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surlymatt
 


Member Since: 23 Apr 2015
Location: Australia
Posts: 4

Australia 2009 Discovery 3 TDV6 HSE Auto Unknown ColourDiscovery 3
Better acceleration with full fuel tank! Why?

My 2.7 diesel D3 is really lazy at getting going, especially in the mornings.

Last year it had an engine swap by a very average mechanic chosen by my insurer and it's never run correctly since then.. In fact, so bad, the insurance company gave up and wanted to write my car off. Anyway, I bought it back from myself, and it isn't right. How hard can it possibly be to get it running correctly?
I put a new turbo on it as the old one was whistling, which made it a bit better.
I fixed the cam timing - which was wrong.
It has an oil leak from the crankcase oil separator - which I assume has a crack in it or a bad o-ring. I haven't looked at that yet, but I'm assuming it is unrelated.

MY question today is:
Why does the performance get a LOT better when i put a tank of diesel in it?
Below about 1/4 of a tank, the car is really sluggish on acceleration from a stand-still.

I haven't checked fuel pressure yet (could be a bad low pressure pump) but that wouldn't explain why it gets better when I add fuel.

Maybe the tank isn't venting correctly, and the LP fuel pump is sucking against a vacuum in the tank?
Is there a vent that need servicing/gets blocked?

A penny for your thoughts.
  
Post #230771815th Sep 2022 12:41 pm
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lynalldiscovery
 


Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274

United Kingdom 2006 Discovery 3 TDV6 Metropolis LE Auto Bonatti GreyDiscovery 3

filter piped up correctly?
  
Post #230774915th Sep 2022 5:44 pm
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loanrangie
 


Member Since: 18 Jun 2017
Location: Melbourne
Posts: 592

Australia 2008 Discovery 3 TDV6 SE Auto Stornoway GreyDiscovery 3

Its a EURO4 so has a spin on filter so cant get that wrong, it was my first thought untill i saw his profile. Does it blow any smoke, IC split or IC hose de laminated ?
  
Post #230777116th Sep 2022 1:25 am
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Flack
 


Member Since: 06 Sep 2006
Location: Preston Lancashire
Posts: 6224

England 2007 Discovery 3 TDV6 XS Auto Stornoway GreyDiscovery 3

Quote:
Maybe the tank isn't venting correctly, and the LP fuel pump is sucking against a vacuum in the tank?
Is there a vent that need servicing/gets blocked?


Try running with fuel cap off that will see if its a venting problem, my guess is its a weak LP fuel pump, the weight of a full tank of fuel above the pump might help to feed it until it get to 1/4 of a tank.
You need to see what pressure is at the valve on top of the engine with ignition on and then running.


Flack Thumbs Up
  
Post #230778316th Sep 2022 6:52 am
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