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....
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.
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.
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.