Intermittant fuel pump problem
Discussion
Can I get some help/advice please? For a starter, I am not a leccy, much perfer a spanner. It is a 98 500 Griff.
Sometimes the fuel pump won't go - sometimes on start up, sometimes in the middle of the road. I had an issue a few months back, when I thought it was the connectors to the pump. Then I gave these a wiggle, and it seemed to fix it. So I replaced these. This worked well for a while (even did Snet). But it is back. I decided the pump was knackered (65k miles/13 years), so I have replaced that, together with more brand new connectors at the pump end. But the problem remains. When I turn the ignition on, I can't hear the pump prime. But then after a random period of time/tries, it goes off fine ... for a bit. But will stop again and I grind to a halt.
So new fuel pump and connections are in. I have checked the 20A fuse, and that is OK. I don't think it is the immobiliser, as the engine will turn. And, if the pump has just stopped -i.e. fuel rail charged (but can't hear the pump), it will run for about a minute(ish). I am down to:
Knackered earth - where is the earth for the back end electrics? Could try cleaning that.
Relay - where is it in that jumble of wires? I am happy to just buy a new one (I am fed up with being stopped at the side of the road) as I have no idea how to test these things. Anyone have the part number handy - and is it LR?
Cut-off. I know where that is, and again, happy to replace (is it LR too?). I think that is OK though. I have had it out, and can check whether I get a circuit when it is on, and don't when I give it a bit of a shake. The 'on' is the two outside wires (Y and YB). I have no idea why there is a middle GB wire. But I don't really know. Said I wasn't a leccy.
Or, is there something else I can try? Cheers chaps,
Roger
Sometimes the fuel pump won't go - sometimes on start up, sometimes in the middle of the road. I had an issue a few months back, when I thought it was the connectors to the pump. Then I gave these a wiggle, and it seemed to fix it. So I replaced these. This worked well for a while (even did Snet). But it is back. I decided the pump was knackered (65k miles/13 years), so I have replaced that, together with more brand new connectors at the pump end. But the problem remains. When I turn the ignition on, I can't hear the pump prime. But then after a random period of time/tries, it goes off fine ... for a bit. But will stop again and I grind to a halt.
So new fuel pump and connections are in. I have checked the 20A fuse, and that is OK. I don't think it is the immobiliser, as the engine will turn. And, if the pump has just stopped -i.e. fuel rail charged (but can't hear the pump), it will run for about a minute(ish). I am down to:
Knackered earth - where is the earth for the back end electrics? Could try cleaning that.
Relay - where is it in that jumble of wires? I am happy to just buy a new one (I am fed up with being stopped at the side of the road) as I have no idea how to test these things. Anyone have the part number handy - and is it LR?
Cut-off. I know where that is, and again, happy to replace (is it LR too?). I think that is OK though. I have had it out, and can check whether I get a circuit when it is on, and don't when I give it a bit of a shake. The 'on' is the two outside wires (Y and YB). I have no idea why there is a middle GB wire. But I don't really know. Said I wasn't a leccy.
Or, is there something else I can try? Cheers chaps,
Roger
As said above first change the two metal cased 12 volt relays in the birds nest by the battery. (They are swinging free and not on the main relay/fuse board). They are special relays with a diode in series with the coil unlike most relays that have a diode (or rectifier) across the coil. Dont insert any old relay you risk damaging your ECU
Bosch part number: 0 332 014 112, most good motor factors will stock them or LR dealers. (about £7 each)
The problem could still be immobiliser related as the immobiliser cuts off:
1. Starter motor feed
2. Ignition coil
3. Fuel pump
So even if your engine turns over and a spark is generated the supply to the fuel pump could still be affected.
The fuel pump supply is also controlled via the ECU so another possible source of trouble or its connections.
Hope its the relay(S) it usually is. In any case worth keeping spare relays in the glove box
Best of luck
Bosch part number: 0 332 014 112, most good motor factors will stock them or LR dealers. (about £7 each)
The problem could still be immobiliser related as the immobiliser cuts off:
1. Starter motor feed
2. Ignition coil
3. Fuel pump
So even if your engine turns over and a spark is generated the supply to the fuel pump could still be affected.
The fuel pump supply is also controlled via the ECU so another possible source of trouble or its connections.
Hope its the relay(S) it usually is. In any case worth keeping spare relays in the glove box
Best of luck
Here's a picture of my birds nest.
There are two fuel pump relays they both have an aluminium case with a red diagonal stripe on the top.
The picture above only shows one the other should be on the blue connector. I cant remember which one is pump and which is ECU but they both operate the fuel system and both need to work.
Be careful if you buy replacement relays as even some specialists get them wrong, make sure the circuit diagram on the side of the relay body is exactly the same as the replacement items.
Cheers,
Simon.
There are two fuel pump relays they both have an aluminium case with a red diagonal stripe on the top.
The picture above only shows one the other should be on the blue connector. I cant remember which one is pump and which is ECU but they both operate the fuel system and both need to work.
Be careful if you buy replacement relays as even some specialists get them wrong, make sure the circuit diagram on the side of the relay body is exactly the same as the replacement items.
Cheers,
Simon.
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