Thread: V8 Discovery Fuel Pump Prob

No worries 4bee. It is a bit of mucking around but no doubt many hundreds of dollars cheaper than a new assembly.

One word of advice though. Don't touch the little wire that connects the fuel gauge to the normal wiring . It is a little bit of conductive string. It looked quite frayed at one point and as soon as I touched it the string broke in half .

I soldered it back together and the arm can still move throughout its entire range but the string has lost some of its flexibility. I checked it with a multimeter and the fuel gauge gives a reading but how long it will last I don't know.

I was going to replace the string with normal wire but I imagine that would harden and snap eventually as well.

For those of you who'd like to see what happens inside a pump when it fails, the following pictures may be of interest. This pump came out of my mate's '95 RangeRover 4.6 HSE. It seems to be beyond repair (but if anyone wants a challenge I can mail you the parts).

First up is the bearing and brush housing at the top of the pump - it has been subject to significant heat, probably due to the brushes beginning to fail and becoming very hot as they make poor contact with the commutator. This has caused the housing to melt, the bearing is almost completely gone and the brushes have fallen over and a lump of nylon(?) has congealed in a spot which seized the rotor.

Second is the commutator which is built as a segmented disk. The heat has severely damaged most of the segments and the brushes have scored the segment surface as they've disintegrated.

Third is the armature which shows signs of the windings swelling with the heat and that has pushed out the the rubber sealing strips from between the pole pieces which has also caused the rotor to seize.

Fourth is the permanent magnet stator and the body - we swaged open the can end to remove the end bearing with a screw driver which is not very pretty. The magnets have been hot but the pump end bearing appears intact - it's the one that gets cooled by the fuel after all.

Final picture is the pump end of the assembly with the filter removed - you can see the pump impeller at right. It was seized when we first inspected the pump.

Undoubtedly not all pumps fail catastrophically like this one, and if the brushes simply wear down and lose contact with the commutator without developing a high resistance joint, there shouldn't be this much heat damage.

Hope you guys find these interesting.

That is certainly one stuffed motor Graham. I should try pulling mine apart again to see what happened. All I managed last time I tried was to break the plastic on top. Although since I have already replaced the motor it hardly matters if I'm a bit heavy on the tools

UM, I think you could afford to apply the "Don't force it, use a bigger hammer" philosophy since you're never going to reinstall it - it would be interesting to perform a post mortem as we did today.

Incidentally, with the Rangie, it's worth bearing in mind that if the fuel pump stops, it could be due to the inertia switch which is mounted behind the driver side kick panel. It's only supposed to operate if the vehicle suffers a sudden stop, like in an accident. There is a small hatch carrying a graphic of a bowser with a lightning bolt through it (not a good combination really!) which you remove to gain access to a rubber shrouded push button on top of the inertia switch. You push the button down to reset it and it should operate with a positive click.

On my mate's '95 Rangie the replacement second hand fuel pump appears to have failed now and during the investigations today I found that the inertia switch had operated. Pushing the rubber button didn't reset it and I had to remove the kick panel and pull out the switch, then remove the shroud and push the mechanism to reset it properly. I could test the switch by tapping the front of it with a screwdriver handle and get it to pop again, but it didn't like resetting with the rubber shroud on at all. This may be a useful tip for Rangie owners - if the vehicle stops dead check the inertia switch but you may find it won't reset properly without taking the thing apart.

The inertia switch appears to be the last place you can check for +12V going to the pump (on the white/blue wire) before it goes to the rear of the car (there are no more intermediate connectors) and it seems you can't get to the pump without dropping the main fuel tank from up in the body floor - I'd be cutting a hatch in the floor under the rear passenger seat for future access while I had the tank out if it were my car, I think.

The outcome in this case is that although I'm sure the inertia switch had operated, the pump still doesn't run and the next step is to drop the tank and check the second-hand pump - I'm pretty sure it'll be U/S.

Maybe this will help someone trace a non-working fuel pump problem in the future. Good luck!

I pulled my old pump apart this morning. The pump and motor spun freely. Mine died due to the brushes failing. One brush was not moving freely in the housing and the other one was worn away entirely. All that was left was the wire and spring

I checked my inertia switch when I had the first problem which in a Disco is behind the windscreen washer bottle on the firewall.

What motor did you use as a replacement and how long did it last?
Perhaps it is a loose wire from the install?

The replacement pump, which I think has now failed too, was a complete pump drop-in assembly (gauge sender, frame, pump motor - the lot) out of a wrecked P38 Rangie. So no, this doesn't shed any particular light on the idea of using an OEM pump motor in the LandRover in-tank assembly. The pump has probably done a few Km's before my mate got it.

When (and if) we confirm that the replacement pump is U/S then we may well replace it with the VN Commodore pump but that's next week's project.

By the way, apparently it's not unknown for the wiring to go open circuit where it comes through the resin block on top of the in-tank assembly, so it's always worth checking the wiring for continuity with a multi-meter at that point too.

UM it sounds like you could try making new brushes for your pump and keeping it in your kit as an emergency spare. I think the hardest part of the exercise would swaging the aluminium case back around the brush holder because of it's inherent tendency to stretch when you pulled it apart. But if you can manage that you should have a viable spare. If you try it, I'll be interested to hear how you get on.

Originally Posted by GrahamH

UM it sounds like you could try making new brushes for your pump and keeping it in your kit as an emergency spare. I think the hardest part of the exercise would swaging the aluminium case back around the brush holder because of it's inherent tendency to stretch when you pulled it apart. But if you can manage that you should have a viable spare. If you try it, I'll be interested to hear how you get on.

I have successfully reassembled the motor from my cousin's 2003 Rodeo fuel pump. However this one was little more ahhh difficult to get apart. There is no possible way that that pump will ever be going back together

Probably just a final note on this, I have just replaced my second fuel pump in as many years.

The first one had seized and on pulling it apart (ok, totally tearing it apart) I saw that my brushes had welded themselves to the armature, disconected themslves from the wire coming down through the springs and jammed the pump impeller at the bottom.

The new pump failure was a bit different. The brushes I suspect were the problem again but in this case the actual black and red wires that come down through the pump carriage had both melted as well, exposing the coil of wire that each one has, to each other and then melting together. I believe this was able to happen as the tank was near on empty so there was air around the wires instead of liquid (fuel). I imagine that the only reason that it failed to "go up" was that it was lacking in oxygen to make it go any further.

I only wonder whether a tank that is kept half to full is less likely to burn out the pump.