JDZ2
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....
Fuel pump power issue...
- Thread starter JDZ2
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JDZ2
Member
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- 82
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- Hersham, Surrey.
....
jamesmartin
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that blue plug relay is fuel pump it will be earthed/switched through ecu, the other plug and relay needs to work before it can
JDZ2
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...
JDZ2
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OK thanks so I need to concentrate on the other one first....
jamesmartin
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yes
discool
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This copy of the pre 95 EFI wiring diagram may help u then, there’s only two relays shown no. 6 and 8, the feed to the pump is clearly shown via the fuse & inertia switch, so for a start, I would check the continuity from the relay pin 87 to the pump plus the the pump earth connection.
JDZ2
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That's very kind of you, thank you.
I have been stripping things back to follow various cables, this should really help.
I also used a slave wire from the earth pin on the black relay plug, running it to the battery. It stopped the relay buzzing when the key was switched off but neither relay is clicking.
One thing I did notice is that there is a 'click' coming from the rear cabin area. Because I am on my own I can't verify where it's coming from until my wife is home later. It got me thinking though, is it possible that the fuel pump works on the bench but something is causing it not to in the tank?
JDZ2
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....I saw the diagram but missed your advice...thanks I will try that.
sierrafery
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The simplest way to check the circuit to the pump is to remove the pump relay and bridge wirh a wire the cavities where termials 30-87 are going, then the pump must kick in if it's not dead and the circuit is OK but from what you describe the problem is with the relay's feed... strangely according to that diagram the inertia swich has nothing to do with relays as in all other cases 
JDZ2
Member
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- 82
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- Hersham, Surrey.
The simplest way to check the circuit to the pump is to remove the pump relay and bridge wirh a wire the cavities where termials 30-87 are going, then the pump must kick in if it's not dead and the circuit is OK but from what you describe the problem is with the relay's feed... strangely according to that diagram the inertia swich has nothing to do with relays as in all other cases
Thanks.
I haven't managed to find the inertia switch regardless.
Just been out to have another look at it....I have found continuity between pin 87 & the plug socket at the pump, so that means there is power, right?
However, I can find no continuity between pin 85 earth & the earth connector on top of the pump, that is the issue, right?
The battery is out of the vehicle being charged again but I will try what you have suggested tomorrow morning, nearly dark now.
discool
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That depends on how your testing, u won’t if using a digital multi meter due to the resistance of the pump motor, so do as sierrafery suggests #30 and bridge relay pins 30 & 87 and when u do the pump will run.
JDZ2
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....whereabouts are you sierrafery?
OK, thanks discool, as I said, I will try in the morning in the daylight.
sierrafery
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That's OK cos those are not connected, pin 85 of the relay is supposed to get earth from the ECU and the pump is earthed to the body
Romania
JDZ2
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Aah, I see...different earthing points. Right, thanks.
Hmmn, I saw on your profile Transylvania but wasn't sure if it was real or not.
What's the situation in Romania regarding the coronavirus?
discool
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Well if your still interest in finding the switch, if its not on the engine bay bulk head similar to the 300series disco then I doubt it’s position is like my old RR and was under the seat with the ECU, but when LR moved the ECU to behind the drivers footwell kick panel on the first EFI disco’s the inertia switch “may” have been moved there also so worth a check.
It’s the same switch as the RR used, so in a small box with a press button on top.
JDZ2
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Yup, I'm curious to know if there is one anywhere. I have already removed the kick panel & had a quick look, although the light was fading & my eye sight isn't the greatest so I'm
not certain but I couldn't see it. I will follow the wiring tomorrow to see if it leads me to it. Was it a Shadow you had?
discool
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Yes I know exactly that situation with my eyesight
Then u may have a birds nest of wiring hiding it, there’s a job accessing the ECU in my disco with wiring and relay in the way, not that I have to go there but I had to have a look-see what was what.
JDZ2
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Yes I know exactly that situation with my eyesight
Morning.....so, the battery is back on & I have bridged the relay pins 30 & 87, & the good news is I can hear the pump, it's working.
The bad news is it still won't start...I have cranked & cranked & flattened the battery.....so the battery is on charge again & I will try again.
Fuel. air & source of ignition...right? I have a spark from at least one plug, the air, well, yes, so it must still be the fuel. Dumb question perhaps but where do I look, how can I see there is fuel available at the engine end? If for example, I let the tank go empty, then put some in, how long would it take, how many turns before the engine starts again?
discool
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Considering all that cranking and not firing I would expect that the plugs to be soaking wet, if so there’s not much hope of starting, there’s a fuel pressure valve on the injector fuel rail or slacken an injector hose to check petrol is reaching the engine.
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