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Topic: Fuel pump / electrics (Read 10563 times) |
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Highlander
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13 Scorpios, XR4x4, Suzuki SJ413 for off road :)
 
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Fuel pump / electrics
« on: May 19th, 2007, 8:50pm » |
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Just been having another look at Alastair's 2.3.
It seems to have an intermittent fuel pump problem.
When the ignition is turned on there is a small amount of petrol pumped through then the flow stops.
The fuel pump gives a slight thump then stops.
Tried another fuel pump on the car and it does exactly the same.
Tried the fuel pump off the car direct to 12v and it runs constantly as it should.
Have replaced relay 17 and no difference, relay clicks fine on ignition.
It seems to be an electrical problem as the car will sometimes start and run perfectly.
Does anyone have any experience in this area?
I'm trying to find out where the feed for the fuel pump comes from, if its definitely 12v and if there is any fancy stuff that might stop it from running correctly?
Stuart
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on Oct 17th, 2011, 12:35pm, Simmo wrote:I give up !  Too much for an old boy!  |
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scorpio_man
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Ford Kuga awd
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Re: Fuel pump / electrics
« Reply #1 on: May 19th, 2007, 9:06pm » |
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hi stuart
could it be the PATS?
when you're talking about the pump stopping, it does after about 3 secs unless you start the engine. or are you saying it's on for less time than that?
hth
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Highlander
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Re: Fuel pump / electrics
« Reply #2 on: May 19th, 2007, 9:15pm » |
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Hi Andrew. It doesnt run as long as 3 seconds. I would reckon theres about enough petrol to fill the lid of a coke bottle and it only runs for a fraction of a second. The Pats seems ok and is not flashing any codes.
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on Oct 17th, 2011, 12:35pm, Simmo wrote:| I give up ! Too much for an old boy! |
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mike
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1996 Cosworth
Posts: 63
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Re: Fuel pump / electrics
« Reply #3 on: May 19th, 2007, 9:18pm » |
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Have you tried bypassing the fuel cutoff (the red button in the boot)? These things can act funny sometimes.
Cheers,
Mike
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Spannerdemon
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Re: Fuel pump / electrics
« Reply #4 on: May 19th, 2007, 9:38pm » |
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Is there a vacuum in the fuel tank preventing fuel from flowing. Might be worth checking your filler cap. Try running the engine (not driving it), without the cap.
A minor fault but one which can cause exactly these symptoms. Basically, if air can't get in, fuel can't flow out. 
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Jonnycab
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Former owner of 2.3 Ultima Facelift saloon
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Re: Fuel pump / electrics
« Reply #5 on: May 19th, 2007, 11:39pm » |
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I've not had the pleasure of dealing with the fuel pump side of things.......yet ....so I'm just having a wild stab in the dark......
Is the fuel guage working properly ?....if not......
Could it be a bad earth to the fuel pump ? 
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Highlander
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Re: Fuel pump / electrics
« Reply #6 on: May 19th, 2007, 11:47pm » |
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Could be any of the above, need to check the wiring i think if i can find out where it goes 
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on Oct 17th, 2011, 12:35pm, Simmo wrote:| I give up ! Too much for an old boy! |
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mike
Junior Member
1996 Cosworth
Posts: 63
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Re: Fuel pump / electrics
« Reply #7 on: May 20th, 2007, 10:12am » |
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12V for the pump is from fuel relay, via fuse F42 to inertia cut off switch (violet/orange wire), thence to pump (violet/orange again).
Intermittent contacts in inertia switches are not unheard of.
Cheers,
Mike
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Alastair
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2.3 Ghia X & MGB Roadster
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Re: Fuel pump / electrics
« Reply #8 on: May 20th, 2007, 2:49pm » |
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Have you tried bypassing the fuel cutoff (the red button in the boot)?
Hi MIke
I am the "proud" owner of the car that has the problem being discussed here and which Highlander is valiantly trying to cure.
Is the red button a fuel cut off or is it a reset button. If its a cut off button then I realy do fancy the idea of bypassing it. I can see the point of a fuel cut off point in race or competion cars (mounted on the outside though) but not hidden away and being yet another thing to go wrong.
JC - the fuel guage is ok and reading is spot on.
SD - yes we think there is a vacuum
Thanks guys - watch this space
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mike
Junior Member
1996 Cosworth
Posts: 63
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Re: Fuel pump / electrics
« Reply #9 on: May 20th, 2007, 3:48pm » |
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Hi Alastair,
This cut off switch is a safety feature: it's an inertia switch which trips if there is a shock, thereby shutting off the fuel pump and lessening fire risks in case of an accident. The red button is there for resetting the switch.
I suggested bypassing it for diagnosis purposes only. But I don't think it's a good idea to have it permanently disabled.
The contacts inside the switch can become oxydised causing the fuel pump to behave somewhat whimsically...
Cheers,
Mike
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Highlander
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Re: Fuel pump / electrics
« Reply #10 on: May 20th, 2007, 9:29pm » |
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Ok, the fuel pump if def 12v so we could try running it direct from a 12v supply, (we were a bit unsure of the voltage before so didnt try this).
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on Oct 17th, 2011, 12:35pm, Simmo wrote:| I give up ! Too much for an old boy! |
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pete from Hull
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Non Scorpio at the moment, but still interested...
Posts: 1365
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Re: Fuel pump / electrics
« Reply #11 on: May 20th, 2007, 9:29pm » |
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I was told that the cut off switch had to be fitted by law on cars with EFI as in the event of an accident the fuel could still be pumping from fractured fuel lines onto or causing fire....There should be a notice in the car advising what to do if it is activated...ref handbook
Pete
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Scorpio_Mike
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Jeep Grand Cherokee 3.0 V6 & 2.8 Sierra XR4i 4x4
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Re: Fuel pump / electrics
« Reply #12 on: May 20th, 2007, 9:47pm » |
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I think the fuel cut off switch is more to do with electric fuel pumps than EFI - in an accident the fuel pump would keep running, pumping fuel as long as there is fuel in the tank and 12v connected to it ! Back in the days of mechanical fuel pumps, engine stops, so does the fuel pump.
I recall when I put a turbo kit on my XR3, had to ditch the mechanical fuel pump and install a high pressure electric one but the engine was carburettor, not fuel injected. Fuel pump was powered through a purple relay - which failed so often I had to keep a spare in the glovebox...seems like this is a weak part as had 3 or 4 failures in my Mk2 Granada 2.8i and a couple on my Sierra XR4i.
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Spannerdemon
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Re: Fuel pump / electrics
« Reply #13 on: May 20th, 2007, 9:54pm » |
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Racking my brains to try and help here. Recently had a vehicle with very very similar symptoms. Fired, ran for 3 seconds, and failed. Absolute COW to find. Turned out to be the Ignition Amplifier. There was a cut off built into it which stopped the fuel flow if there was insufficient power in the ignition circuit.
Don't know if Scorpio's have these, but just a thought?
Also, years ago, had a guy with almost exactly this problem. Turned out someone had put sugar in his fuel tank. Effectively and totally blocks the system. Not nice to suggest, but you never know...... 
The ONLY other thing I'm now going towards, is a plain old fashioned blockage somewhere in the fuel system. Collapsed pipe/hose. Foreign body, broken or deteriorating component within the fuel system or similar?
You could always blow back into the fuel tank with compressed air. Can sometimes clear almost impossible to find blockages in the actual fuel delivery tubes on the tank itself. However, if this clears the obstruction, then you'll need to remove and flush or replace the tank, as it will surely happen again.
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Highlander
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Re: Fuel pump / electrics
« Reply #14 on: May 20th, 2007, 10:44pm » |
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Dont know about the blockage, the pump doesnt run for more than a split second, the second pump we connected to the car did the same but when this pump was connected to 12v it ran constantly.
I think we can replace/bypass the fuel cut off switch, if that doesnt cure it we can try a direct 12v feed to the pump while cranking the engine
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on Oct 17th, 2011, 12:35pm, Simmo wrote:| I give up ! Too much for an old boy! |
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Snoopy
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Re: Fuel pump / electrics
« Reply #15 on: May 21st, 2007, 7:12am » |
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The reason why the pump stops when you switch on. IF the engine is NOT running there is a pressure sensor in the fuel line. When it reaches working pressure it switches OFF.. The one you tested on the bench was just free running and thats why there is a difference in behaviour.
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Highlander
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Re: Fuel pump / electrics
« Reply #16 on: May 21st, 2007, 7:39am » |
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We had the fuel pipe off though Dave, there was no pressure.
plus the second pump/tank gave the same result even though there was no petrol in it
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on Oct 17th, 2011, 12:35pm, Simmo wrote:| I give up ! Too much for an old boy! |
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Snoopy
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Re: Fuel pump / electrics
« Reply #17 on: May 21st, 2007, 9:26am » |
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Sorry slightly misread your post and others have suggested what I would so Sorry can't help any more ATM will keep thinking.
Dave.
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Spannerdemon
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Re: Fuel pump / electrics
« Reply #18 on: May 21st, 2007, 12:48pm » |
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Have you checked the roll-over valve. May be blocked, fractured or jammed?
HERE
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Dave2302
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Re: Fuel pump / electrics
« Reply #19 on: May 21st, 2007, 1:27pm » |
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Hi Stuart,
Just some more thought ......
The way the system works is the ECU supplies the signal to trip on the fuel pump relay which then sends 12 volt to the pump safety switch then to the pump.
AHBS, my first check would be safety switch, then monitor the signal to the fuel pump relay from the ECU.
I have had vehicles before which lose the signal from the ecu for some reason then they don't run the fuel pump as they should.
Only cure is an ECU change.
HTH Regards Dave
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