Question about 2003 Land Rover Discovery

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Fuel pump relay is not being activated, and when i do activate it it still wont start. But fuel pump does work.

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  • eyelash99_20 Jun 18, 2009

    Relay is not being activated to activate the pump. Can activate the relay by means of an earth wire BUT it still does not start.

  • yadayada
    yadayada May 11, 2010

    what is the relay doing exactly

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Have you checked that the inertia switch has not been activated somehow?

Posted on Feb 24, 2010

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94 s10 fuel pump relay clicking no start


The clicking noise at the relay indicates that the relay is bad, or that the wires to the relay and/or connector is bad.

A relay is an electronically activated switch. Inside is a coil. When 12v+ is applied to one end of the coil, and a ground is applied to the other end, the coil gets charged, creating a magnetic field. This magnetic field literally moves a metal lever from position A to position B. One end of the lever is attached to constant battery power. When coil not energized, the lever rests in postion A (which in the case of the fuel pump relay is feeding the battery power to an unused terminal). When the coil is activated, the lever moves to position B (which in this case is a terminal connected to your fuel pump wire). Thus, when the relay is activated, 12v+ is being directed from the battery to the fuel pump.

This fast clicking indicates that the relay coil is not getting a constant voltage or ground supplied to it, thus the lever is moving back and forth between position A and position B, either there is a wiring issue, a connector issue, or an internal issue with the relay.
The relay has 4 wires, black, grey, orange, green with white stripe.
black = ground
orange = battery = 12v+ always
grey = wire out to fuel pump (on some cars this wire is tan with white stripe)
green/white = signal wire from ECM

When key is turned ON, the ECM sends 12v+ out on the green/white wire to the relay for about 2 seconds - this activates the relay coil for 2 seconds, thus running the pump for 2 seconds (priming). When the vehicle is started, the ECM sees a constant ignition signal from the ignition module, and sends a constant 12v+ out on the green/white wire, thus activating the relay coil constantly, and thus running the pump constantly.
When car shut off, no more constant ignition signal, thus ECM stops sending the 12v+ out on the green/white wire.
So, you can kind of test your connector ...
1) remove connector from relay
2) jumper a wire from the slot for the orange wire to the slot for the grey wire - fuel pump should run - wiggle wires to verify at connector
3) probe black wire slot with ohm meter - make sure black wire has constant ground - wiggle wires at connector
test relay ...
1) remove relay from connector
2) rig a ground wire to the tab that had the black wire when in connector
3) apply 12v+ to the tab that had the green/white wire - relay should click once and do this every time you apply the 12v+

That should help you track it down to either a connector problem, a wiring problem, or a relay problem.

Nov 28, 2015 | Cars & Trucks

1 Answer

95 bmw 325i cranks but wont start.Has fire to plugs,checked fuel pump fuse, relay and main relay,no ground to fuel relay socket,no hot or ground going to fuel pump,,suspect DME ??? Was running fine un


Try to disarm the alarm system first,if that doesn't work,try your spare key,if it works the key is faulty.if this fails,put it on diagnostic machine.,since it can be EWS.

Oct 18, 2014 | BMW 325 Cars & Trucks

2 Answers

My 2005 l200 wont start but if you run a lead from battery to switch on pump it starts take lead of and it stops new switch on and still no start.


The fuel pump is powered from a relay. That relay is powered by the engine's computer ("ECU"). The relay is necessary to scale the low current control signal from the ECU into a high current switch to operate the fuel pump. The high current circuit will likely contain a fuse. That fuse or the fuel pump relay may be defective.

The fuel pump relay is activated for a few seconds when the ignition is turned on before starting the engine. If everything is working properly, you should be able to hear the fuel pump run for those few seconds before starting the engine. This is so the injectors have adequate fuel pressure before the engine is started.

Apr 11, 2014 | Mitsubishi Pickup Cars & Trucks

1 Answer

Put on new fuel pump got pressuer but want stay cranked


Your post is lacking any detail. However, if you are stating that the engine starts after being cranked but dies out (wont stay running) there are 2 ways the fuel pump is activated. When the key is first turned on, there is a 5 second fuel pump run (the ECM energizes the fuel pump relay). After the engine starts, the fuel pump relay will only stay energized when the oil pressure switch closes keeping the fuel pump relay on (oil pressure is above 5-7 psi). If the oil pressure switch is faulty or there is no oil pressure, the engine will stall just after starting.

Apr 10, 2014 | 1999 Chevrolet Astro

1 Answer

1986 ford f150 tested fuel pump with cables,pump runs no power when hooked to wires going to tank, is it relay


THIS IS ALL ON MEMORY SO GET YOURSELF A WIRING DIAGRAM FOR THAT TRUCK!!!
If you have one you should install an inline fuel pressure gauge to verify that you are indeed not getting fuel pressure first. Assuming you have no fuel pressure, it could be one of a few things.
check all of you fuses
if ok, check fuel pump relay for activation during engine cranking. I believe in that vintage Ford, the oil pressure switch is responsible for activating the relay. So with a test light backprobe the activation wire at the relay. if you get activation power at the relay, and no relay activation, then yes it is the relay, but if you get nothing, then it will be the oil pressure switch. If you get activation to relay and still no pump activation then you might have a break in the wiring OR the fuel pump has short brushes.

I know thats alot to take in but hey thats what a diy forum is for right? Good luck!!!

Dec 28, 2012 | 1986 Ford F150 SuperCab

1 Answer

I replaced the fuel pump....car still wont start...do you think it is the relay switch 2006 325i


The relay should have been trouble shot BEFORE changing out the pump. If you've got 12v at the pump it is not the pump. Unless you installed a bad pump. But, no 12v at the pump= bad relay. But ten you've got to see what activates the fuel pump relay.

Jun 21, 2011 | 2006 BMW 3 Series

2 Answers

2002 pontiac grand am, new fuel pump and filter, wont start


Is the security light active? If yes it will have to get reprogrammed by the GM dealer as GM has this as a propriatory system... Meaning no one else can work on it.

Sep 14, 2009 | 2002 Pontiac Grand Am

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