LR3 2006 4.4ltr, fuel issues which Land Rover cannot diagnose

**shedlock2000** · 9th August 2015, 02:14 PM

Originally Posted by rangeyrover;2403904
Edit: unless the FCO line is a sensor, rather than a control.
In other words the FCO becomes active and that is then sensed by the ECM
[URL="http://www.vw8848.net/view_8s278qyfycjhwmu1.html"

Maybe this electrical diagram can help?[/URL]

From what I am told, the FCO is an output from the ECM which reduces the injector opening to limit rpm. It's actually not doing this very well as the fuel seems to be restricted -- rather than cut off. In other words, the cut off become progressively worse rather than OFF.

I have noticed, though, that the FCO triggers to 'ON' as the key is turned to start started (twice, in fact), though this 'ON' only lasts for an instant. On reflection, it seems like the ECM is looking for information during start up, and switches the FCO 'ON' when it doesn't find it -- then it seems to get it and be happy until something on the engine or fuel side heats up enough to trigger the coming 'ON' again. I wondered if the ECM is having issues grounding the sensors it receives inputs from, and if this is the reason why it decides to cut fuel?

**shedlock2000** · 9th August 2015, 02:41 PM

Originally Posted by rangeyrover

Maybe this electrical diagram can help?

Thanks for this great resource!! Its for a RHD (mine is LHD), but its still going to be extremely useful. I wonder, do you have access to the location points for the grounds and sensors etc? I believe its in the workshop manual under 'Locations'. But it is not listed in the wiring diagram.

**letherm** · 9th August 2015, 03:29 PM

Originally Posted by shedlock2000

Thanks for this great resource!! Its for a RHD (mine is LHD), but its still going to be extremely useful. I wonder, do you have access to the location points for the grounds and sensors etc? I believe its in the workshop manual under 'Locations'. But it is not listed in the wiring diagram.

Hi.

You may find this useful. Full workshop manual collection for D3 etc. D3 currently $18.50. DavesITShop is run by the owner of this site Incisor. You'd have to ask him via PM whether he can/will post overseas but the cost is $18.50 Australian. Might be handy to have for future reference even if not now. I have just bought the D4 version and, from my initial scan, it looks like it contained all the wiring diagrams and error codes as well as the usual workshop manual content. It also had the drivers manuals.

https://www.davesitshop.com/emporium...ls-cd/dvd.html

Regards,
Martin

**shedlock2000** · 9th August 2015, 04:51 PM

Thanks, Martin. I'll absolutely get in touch with him about this. I have a ten-day window in which to fix my LR3, so it may not work for this issue, but it'll certainly be handy! Thanks for the suggestion!

**shedlock2000** · 11th August 2015, 08:07 AM

Update:

After a day of exhausting testing, here is what we can say for sure:
Physical fuel pressure at fuel rail drops progressively from 62psi to 20psi whereabout the vehicle stalls.
Fuel pump has been supplied with a false feed (bypassing the relay) and problems still present.
Fuel pump is audible when pressure is good, fuel pump is not audible when pressure is low.
Fuel pump grounds and feeds have been checked.
ECM switches on its Fuel cut off 'ON' about the same time that the pressure can be seen to drop (why her it causes the fuel pressure drop, or responds to it is unclear).
Fuel problems reset when key is cycled -- sometimes it resets after 1 cycle -- sometimes it takes a few cycles.
All ECM grounds have been checked and are good; fuel pump feeds have been checked and found to be good and continuous.

All this seems to point to a fuel pump, but has anyone heard of a resetting fuel pump?

**Eevo** · 11th August 2015, 08:32 AM

almost like there is a resistor build up in the fuel pump until its de energised.

**Cambo_oldjaguar** · 11th August 2015, 08:33 AM

Have you got a clampmeter that can measure the current going to the pump, just clip it on to the power feed to the pump. Also monitor the voltage too.

Not sure exactly what sort of amps it should be pulling normally, but if you can see what the difference is from when it's putting out 60-odd psi and when it drops, might be useful to know.

I can't seem to download that wiring diagram, is this one of those PWM driven pumps with a variable speed? Or should it just run at the one speed?

**shedlock2000** · 11th August 2015, 09:50 AM

Originally Posted by Cambo351

I can't seem to download that wiring diagram, is this one of those PWM driven pumps with a variable speed? Or should it just run at the one speed?

I'm not sure what a PWM pump is. The physical item just has two wires and looks like any other pump. Surprisingly, it's not a screw pump but sounds like a solenoid pump. That's all I can tell you. According to the wiring diagram I have, it's just one wire to the pump from the pump relay. The ground disappears up the back 'D' post. There seems to be feeds to a pump leak detection module -- but I think that is an evap. thing.

**Cambo_oldjaguar** · 11th August 2015, 10:12 AM

PWM = Pulse Width Modulation, instead of a flat DC voltage it's a square-waved pulse signal, used to control the speed of a fuel pump.

But if there is a just a relay switching the pump on/off then it's just going to be a plain DC voltage and the pump has just one speed. Much simpler.

So my question is what's going on with the power supply to the pump, is it stable? Is the current consumption of the pump "normal"?

But it does sound like the pump is failing as it warms up. This would also fit with what you said about it taking longer to happen with a full tank of fuel.

I know i'd be reluctant to throw a new fuel pump at it without being sure...

Have you measured the resistance of the cables to the pump?

**shedlock2000** · 11th August 2015, 01:10 PM

Originally Posted by Cambo351

So my question is what's going on with the power supply to the pump, is it stable? Is the current consumption of the pump "normal"?

Yeah, the voltage is a stable 13.2, as is the amperage drawn by the pump: it starts at 5.2A and peaks at 6.4A; it settles down to 5.75A

But it does sound like the pump is failing as it warms up. This would also fit with what you said about it taking longer to happen with a full tank of fuel.

I have put 4 gallons of fuel in tonight to test the theory (while it was playing up) and it didn't make much difference. I also stopped and quickly exchanged the fuel relay for a jumper line and that didn't affect it either. What I can tell you, is that the fuel pressure was all over the place this evening after we got the engine hot by idling. The pressure would start of the key at 62psi then steadily drop to 50 psi. It had a moment of dropping to 30 psi, but after about 1 minute jumped up sharply back to 62psi. It's now hovering at idle between 45 and 55psi. When the pressure drops, the fuel trim alters to suit.

I know i'd be reluctant to throw a new fuel pump at it without being sure...

Tell me about it! She's had $2500 on her already, and this will be the second pump I'm thinking of putting in. I don't know how long the LR3 this tank and pump came out of was stood, but I can't see that affecting the pump badly -- unless they had drained the tank early on and the pump dried out? That doesn't explain the reset, though. What I think might, is a faulty pressure regulator on the pump. If the pressure regulator is failing, then it's possible that the few seconds that the fuel pump is off is enough for the mechanism to return to normal and then take time to fail open and release fuel into the front push-pump in the tank.

Have you measured the resistance of the cables to the pump?

No, it's impossible to do without dropping the tank. I shall order a pump tomorrow and measure the resistance in the feed wires then. Unless you guys can think of anything else, I'm running out of ideas now.

Good voltage, good amperage, no difference between the relay and a jumper lead over the electrical supply, good grounds for the ECM, fuel pump, and for the engine. But poor and varying fuel pressure at the fuel rail reset by a key cycle (though the hotter the engine and fuel the more quickly the symptoms recur).

The ECM fuel cut off 'ON' cannot be contributory as the fuel rail pressure is what fluctuates -- the cut off reduces the dwell time on the injectors.

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