Defender 2002 TD5 - Running fine on a 30 mile trip. Then on its return it started losing power and stopped on M4. Got recovered by AA, the AA man said it was Pump Failure.

After buying new pump (VDO) and fitting it, it still didn't work. Checked the old pump with direct connection to battery and it was OK! Checked new pump with direct connection and it was OK!

So
1. Replaced Relay - no change. Inspection from top suggested the connectors look ok.
2. Replaced 20A Fuse - no change
3. Tested Direct Earth from Batter - no change
4. Measured voltage at Pump - 11.3/11.5 volts, so appears to be too low to fire.

Can't really see wiring as it's within a black protective loom.

Schematics suggest Live is Battery > 20A > Relay, which has a live from the ECU to latch it, and send current down to pump.

Ideas pls?

Mark Monkey said:

Defender 2002 TD5 - Running fine on a 30 mile trip. Then on its return it started losing power and stopped on M4. Got recovered by AA, the AA man said it was Pump Failure.

After buying new pump (VDO) and fitting it, it still didn't work. Checked the old pump with direct connection to battery and it was OK! Checked new pump with direct connection and it was OK!

So
1. Replaced Relay - no change. Inspection from top suggested the connectors look ok.
2. Replaced 20A Fuse - no change
3. Tested Direct Earth from Batter - no change
4. Measured voltage at Pump - 11.3/11.5 volts, so appears to be too low to fire.

Can't really see wiring as it's within a black protective loom.

Schematics suggest Live is Battery > 20A > Relay, which has a live from the ECU to latch it, and send current down to pump.

Ideas pls?

Click to expand...

11volts should be enough to run the pump, if it also has the amps to back the voltage up.
So you need to start measuring from the ecu end and work your way down, as it could be wiring/connector or relay.
All fuses good? even unrelated ones can have other functions.

Is the relay live coming from the ecu
Is the earth side of the relay good?
Is their power to the relay for the pump?
If there is power does power come out the relay when you trip it?

Once you have checked the volts and come to the conclusion that a voltmeter is pretty crap for checking for power you then need two bits of wire and a light bulb, bulb can be any watts but bigger is better ie hlamp bulb for example, if shes bright then you know the power is good.

lynall said:

11volts should be enough to run the pump, if it also has the amps to back the voltage up.
So you need to start measuring from the ecu end and work your way down, as it could be wiring/connector or relay.
All fuses good? even unrelated ones can have other functions.

Is the relay live coming from the ecu
Is the earth side of the relay good?
Is their power to the relay for the pump?
If there is power does power come out the relay when you trip it?

Once you have checked the volts and come to the conclusion that a voltmeter is pretty crap for checking for power you then need two bits of wire and a light bulb, bulb can be any watts but bigger is better ie hlamp bulb for example, if shes bright then you know the power is good.

Click to expand...

Thanks, I'll start to work down that list. All fuses looked good - and the relay was replaced. Good point on Volts vs Amps, not familiar at all with this, but whilst its getting 11+v its not firing unless I take direct from the battery, so its not getting the amps by the look of it. Off I go wire checking ..

Mark Monkey said:

Thanks, I'll start to work down that list. All fuses looked good - and the relay was replaced. Good point on Volts vs Amps, not familiar at all with this, but whilst its getting 11+v its not firing unless I take direct from the battery, so its not getting the amps by the look of it. Off I go wire checking ..

Click to expand...

Always check a fuse with a bulb or just replace it to be sure, they can be real buggers to see especially the darker coloured ones, green/brown etc, red and yellow normally easy to see.

Mark Monkey said:

Defender 2002 TD5 - Running fine on a 30 mile trip. Then on its return it started losing power and stopped on M4. Got recovered by AA, the AA man said it was Pump Failure.

After buying new pump (VDO) and fitting it, it still didn't work. Checked the old pump with direct connection to battery and it was OK! Checked new pump with direct connection and it was OK!

So
1. Replaced Relay - no change. Inspection from top suggested the connectors look ok.
2. Replaced 20A Fuse - no change
3. Tested Direct Earth from Batter - no change
4. Measured voltage at Pump - 11.3/11.5 volts, so appears to be too low to fire.

Can't really see wiring as it's within a black protective loom.

Schematics suggest Live is Battery > 20A > Relay, which has a live from the ECU to latch it, and send current down to pump.

Ideas pls?

Click to expand...

When my td5 stopped without warning there was no power going to the pump. On ignition the engine management light wasn’t lighting up. Turned out to be ecu failure

When the TD5 Land Rover stops, everybody says fuel pump. In my case it never was the fuel pump, but almost invariably an electronic problem, such as ECU failure or wiring loom problems. So beware the instant diagnosis.

I'm sure you've worked this out but there's a wire coming out of the ECU to the fuel pump relay under the seat, which activates the relay - i.e. switches on the current to the fuel pump. It's effectively an ignition switched live. So it should be fairly easy to test this one with a meter. It should also be possible to see what's coming out of the relay towards the pump when it's on - it's a fat white and purple wire as I remember. Then at least you can begin narrowing down where the voltage drop is. Relays can deteriorate. I used to have one which made the engine note change when I wobbled it, which wasn't exactly confidence inspiring.

Don't forget, in a healthy TD5 the fuel pump doesn't run all the time. When it thinks it's built up enough pressure it switches off again, and comes back on when the engine's used a bit (or it's leaked out on the floor). This function appears to be inside the pump, as the ECU wire is live all the time the ignition is switched on. It may simply think it's up to pressure so let a little fuel out, perhaps by unclipping one of the fuel lines. I find the one that goes into the fuel pressure regulator is usually the cleanest and easiest to get at.

My understanding of the fuel system is the pump runs continuously and fuel pressure is controlled by the fuel. Pressure regulator and excess fuel spills back to the tank after going through the fuel cooler.