RangeRovers.net Forum banner

1 - 6 of 6 Posts

·
Registered
2002-2005 Range Rover MkIII / L322
Joined
·
10 Posts
Discussion Starter #1
I really hope someone on this forum can help me with my very peculiar problem.
Vehicle. Range Rover L322 2005 BMW 4.6 ltr petrol engine; UK model. Sparingly used; total mileage: 42000 km.

Runs beautifully when the fuel tank is between ½ to full.
As fuel level approaches ½ tank, engine starts rough running.
If vehicle is idling for some time (eg red traffic light), vehicle loses power and is unable to accelerate and will occasionally die.
When engine is restarted which it does easily, it runs fine for a couple of minutes and then again starts missing.
If accelerator is nursed, the engine will accelerate slowly. If accelerator is used normally, engine stalls.
Refilling the tank makes the problem go away.

Dealer first said clogged fuel filter; changed filter …. No change; fault persisted.
Next, Dealer said that the fuel level gauges are bad. Change them.
Complete fuel assembly removed, gauges in both fuel tank looked good; general cleaning carried out, pump checked, very nice, quiet, healthy hum.
Fuel level gauges report correct values when checked via Test No 6 in the Instrument cluster testing.
Reinstalled. Problem persisted. New problem surfaced; fuel level being reported inaccurately at the instrument cluster.
Reopened the tank, took out the fuel assembly again, dealer adjusted something; fuel level being reported accurately now.
Dealer now wants me to install a brand new fuel assembly; the complete thing; not just the pump.

Decided to do some troubleshooting on my own....
  • Checked fuel pump relay; all relays in the rear fuse panel do get warm….. fuel pump relay also quite warm.
  • Relay swapped with another; engine missing stopped for about 15 miles and then reappeared.
  • Checked voltage at relay. When ignition switch is turned on, 12 Volts appear for a short while and then drop to 8.5V.
  • Checked all other relays in the rear fuse panel (heater, blower, radio etc.) and they stay at 12 V.
Now, Questions.
Why does the voltage supply to the Fuel Relay initially show 12V when key is turned on but then it drops to 8.5V after a couple of seconds? IS THIS NORMAL?
Why does the engine perform flawlessly when the tank is full?
What has fuel quantity to do with engine performance?
Is it an electrical problem within the tank which only manifests itself when some portion of the fuel tank assembly is not immersed in fuel?
Is it an intermittent pump due to intermittent voltage?
According to the Dealer I need a complete new fuel pump assembly. That is a major expense which I would like to avoid.
If the fuel pump is failing, the problem should be present even with a full tank, should it not?
I would like to remove the fuel tank assembly once again (the dealer has done this thrice already) and carry out some trouble shooting.
The main thing is to check the pump itself. There are posts that say that the pump can be serviced; bushes replaced. Is this a good idea?
Could there be an airlock being created within the tank hoses etc and if so, what do I need to check?
Could there be a power supply problem to the pump? What do I need to check to obviate this possibility?
Could there be fuel starvation due to a leak within the pipes inside the tank itself? (there is no fuel leak from anywhere and fuel mileage is normal).
Should I spend this weekend opening up the fuel tank pump assembly or should I just let the dealer install a new one?
I don’t want a repeat of the fuel filter replacement or a couple of other (non fuel related) issues in which he replaced parts but did not fix the problem.
I REALLY HOPE THAT YOU GUYS CAN HELP ME OUT ON THIS ONE......
HANKS IN ADVANCE.
 

·
Registered
Joined
·
1,758 Posts
Interesting point on warmth of relay but the truer point might be the voltage drop.. Is it possible that the ground for the fuel prevents the maintenance of full voltage. Not sure where the ground point is for the pump. The other possible point may be the fuel pump motor is worn, similar to a worn starter motor but then the amp draw would increase. There are motors available to change over. I have planned to get one in case as they are a lot cheaper than the whole assembly. With a full tank the weight of it might be deflecting slightly which allows things to work properly. was your voltage drop there with a full tank or a half tank or both. keep us posted. i am researching a fuse #9 blowing issue which has recently escalated. i viewed storey wilsons' video on intermittent relays which is worth viewing.
 

·
Registered
2002-2005 Range Rover MkIII / L322
Joined
·
10 Posts
Discussion Starter #3
Thanks for the feedback.... voltage drop is with all fuel levels. Have read all posts on this subject (I think) and nowhere does it mention that the voltage coming to the fuel pump relay should drop to 8.5 after a couple of seconds of turning the ignition on. When I crank the engine the voltage goes up to 12 volts and the car starts fine. I am really stumped on this one.
 

·
Registered
2006-2009 Range Rover MkIII / L322
Joined
·
3 Posts
Hey Falcon. I am new to the Ranges but this problem is common on car with the fuel tanks divided in two parts by drive-shaft. While the main fuel pump is OK (in your case) the secondary unit (usually not electrical) is not functioning for some reason. That is usually injection type pump, that uses the excessive fuel from the main pump, to pickup the fuel from the other half of the tank. Reasons of the failure could be different but usually narrowed down to popped line, failed fuel return valve (sometimes integrated into fuel filter), or clogged primary filter on the injection type pump.
Unfortunately to find it out, you will need to remove the pump assembly and check it physically.
As to the voltage it could be (If you car has returnless fuel system) the FPDM that regulates the pulse width.
Anyway, it has nothing to do with your problem.
 

·
Registered
Joined
·
1 Posts
Hi Falcon. Recently, I've purchased a Rover like yours in Doha. The truck has the same problem you mention here. Still, I haven't changed anything, but my first call is to change fuel pump and fuel filter. But as you mentioned in your post...didn't work. Finally, how did you solve the issue? Many thanks
 
1 - 6 of 6 Posts
Top