Where is the fuel pump relay

[z_chromozonehome]

Hi guys,

after a merry Christmas I have decided to have a go at fixing my fuel pump power feed. Now I have a copy of the bible and a multimeter and I was expecting the job to be a little tricky, but it's driving me mad

I have followed the black and yellow wire that feeds the pump back through the body and down the sill into the footwell. It then has a kind of in line fuse and connects to a yellow wire that goes into a connector box. The loom then snakes away under the dash by the transmission tunnel. Where does it go? The diagrams show a relay which I would expect to find in the footwell some where with the other relays. I cannot find a relay with any of the coloured wires coming from it indicated in the diagram. I don't want to start removing my dash to find the thing. Can some body please tell me what it looks like (colour/size etc), and if it has a serial number on it.

Thanks for listening,

Z

[z_chromozonehome]

I have taken a more relaxed approach to the wiring diagram and I think I have found it.

Does small inch square silver box ring any bells,
Bosch #0332014112.

Wonder where I can get a new one today, it must be a standard part off of one type of car. Range Rover??????????

I think I have started a new kind of message board, where I ask my own questions and post my own answers, seems to be working ok for now

Z


Indeed the relay is from a range rover, so I'm off down the local dealer to see if they have one.

>> Edited by z_chromozonehome on Saturday 3rd January 12:01

[GreenV8S]

Glad you've found it. On the RV8 powered cars the fuel pump relay is a Bosch relay in a metal case, costs £15 or so from your local Landrover dealer. There's nothing particularly magical about it except it's a twin pole relay - most relays with this pin configuration are changeover relays. When you come to replace it, use an ordinary spade terminal to check that eac of the terminals in the socket is a reasonably tight fit. If these have relaxed it can cause the socket to overheat which takes out the relay and will take out the new one too. Also remember to tape the relay into the socket, you should do this with all relays to prevent them moving and working loose.

[ratman]

Had a similar problem when my relay packed up last year. Just to let you know you are not alone - none of the wiring conformed to the colours in the wiring diagram and it became a case of trial and error. My local accessory shop had a catalogue with relay diagrams and pin connections in it. I just found one of the correct rating with the corresponding pins at £4.99. Further details on the forum if you want to search. Regards Ian.

[z_chromozonehome]

Hi guys,

I have replaced the relay, but still no go. The multimeter is telling me strange things that I don't understand.


Firstly, with the ignition off I have two live feeds at 12.6 V, white wire with orange square (87) and brown and green heavy guage (30) at 12.6V. I also have white (86) and green at 0 and blue (85) at 0. The purple and white feed wire (87) has 0.02V! This decreases if you keep the probe on.

With ignition on and immob off the two 0V wires now have 12.6 V feeds as well. But the feed wire has 0.3V which falls as the probe is connected. This I do not understand. There is another wire coming from the feed that is white with a purple suare on it and a smaller guage, what does this do. Is is something to do with the immob.

Do you think it is an immob problem.

Please help,

Z


>> Edited by z_chromozonehome on Saturday 3rd January 15:30

[GreenV8S]

z_chromozonehome said:

lots of complicated stuff

I kind of lost track of which wires you're talking about I'm afraid. Each time the fuel pump supply plays up on the V8S my understanding of how it is supposed to work improves a bit more. I now have a really very amazingly clear picture, and lots of grey hair. But it does now work properly, fingers crossed.

I'll try to explain how the supply works on the V8S, but I wouldn't assume yours is wired identically. I can also give you some pointers to track the problem down.

First how it works on mine:
There are two circuits through the relay. The control circuit which switches the relay is connected to terminals 85 and 86. One side has a switched fused supply from the ignition. On mine, this also goes through the immobiliser. The other side is 'earthed' via the ECU when the ECU wants the pump on. The normal behaviour is: disarm imob and switch ignition on, 12v is fed to terminal 85, ECU takes terminal 86 low (down to about 3v on mine), fuel pump primes, after a moment the ECU takes terminal 86 high and the fuel pump stops priming. If I then turn the engine over, the ECU takes 86 low again to run the pump. 85 and 86 might be swapped over on other cars but you will soon recognise which is which because one has a switched ignition feed.

The second circuit through the relay is the main power feed to the pump. Terminal 30 has a permanent fused 12v supply. When the relay operates, the relay connects this to the output terminals 87 and 87a. On mine, 87a powers the lambda sensors and 87 powers the pump. The feed to the pump goes via the inertia cut-off switch which is under the bonnet at the front of the passengers footwell. This returns the length of the car to the big terminal on the pump, the other terminal is permanently earthed.

Favorite problems are: intermittant relay failure (goes open circuit when hot), relay loose in its socket, blown control circuit fuse, blown power circuit fuse, either fuse loose in the fuse panel, corroded contacts anywhere, corrosion in the inertia cut-off switch, damaged or corroded wiring at the pump.

To start with I would prove the pump works by sticking 12v direct from the battery to the 12v terminal. This is also a good get-you-home bodge if it starts playing up when you're away from home. After all the problems I had, I now keep a fused lead the right length with jumbo spade to fit the pump at one end and a croc clip to fit the battery at the other. I've used it quite a few times now!

The second thing to check is that the pump runs when you bypass the relay. Pull the relay out of its socket, check you have 12V on terminal 30, take a 20A fused wire with a male spade terminal at each end and connect one end to the relay socket terminal 30 and the other end to the socket terminal 87 (the one which is opposite terminal 30). If this doesn't work, try 87a (the one in the middle) in case yours is wired differently to mine. If this doesn't work, I'd suspect a problem with the inertia cut-off switch or a wiring fault. Conceivably, it could be a blown fuse if yours has the fuse after the relay rather than before it. You can reset the inertia cut-off by pulling the button up and down a few times, but if this is the problem it is likely to come back and you need a more permanent solution (I fixed mine by taking it off the car, following the wires back to the main loom and short-circuiting it, and then hitting it hard several times with a large hammer - cheered me up no end).

If the pump works OK with the above but not when you put the relay back, check you are getting 12V between 85 and 86 when the pump should run. If so, the relay is duff or not connecting to the socket properly. Otherwise, the fuse in the supply to 85 may have blown, or the imob may be playing up, or you have a wiring fault in this circuit.

Hope you have a lot less hassle solving this than I did, but rest assured you *can* fix it if you keep plugging away at it! Let us know how you get on.

[z_chromozonehome]

Thanks Green V8S,

it finally did turn out to be the relay. It was the priming part of your post the made the penny drop. I was looking for a constant live from the relay output to the pump, but the wire was only live for a short time after turning on the ignition. I missed this with the multimeter. Once I had connected the pump with the new relay I could hear it priming, turned the key and bingo

Thanks again to all,

Z