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post #1 of 8 (permalink) Old Apr 3rd, 2008, 8:48 pm Thread Starter
 
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fuel pump always running

I have a 88 k75 and the only way I can get the fuel pump to stop running is to unhook the battery. Anybody know what may be done to fix this?
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post #2 of 8 (permalink) Old Apr 5th, 2008, 11:11 am Thread Starter
 
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Question

Quote:
Originally Posted by bootlegjack1
I'm a newbie with a 88 k75. When I cut the engine off the fuel pump keeps running. The only way I can get it to stop is unhook the battery.
Anybody know what I can do to fix this or tell me if it's normal?
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post #3 of 8 (permalink) Old Apr 5th, 2008, 2:19 pm
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Ok, are you sure it's the fuel pump and not the starter? I only ask because the starter has come up many times and it's a stuck relay. Removing the battery cable is the only way to stop it until you take care of the relay.

I believe the fuel pump has a relay as well and may act similarly. I'm not sure if the power for the fuel pump goes through additional contacts other than the relay. Best approach for both scenarios is to remove the relay, and either whack it a couple of times to see if you can free up the contacts, or replace the relay.

Make sure the battery is fully charged before you re-connect the battery cable, or you may "weld" the contacts of the new relay as well.



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post #4 of 8 (permalink) Old Apr 6th, 2008, 7:59 am Thread Starter
 
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I'm sure it's the fuel pump because I can unplug the wires at the back of the fuel tank and it cuts it off. I'll look for the right relay and try what you suggested - thanks for your help!
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post #5 of 8 (permalink) Old Apr 6th, 2008, 8:40 pm
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Quote:
Originally Posted by bootlegjack1
I'm sure it's the fuel pump because I can unplug the wires at the back of the fuel tank and it cuts it off. I'll look for the right relay and try what you suggested - thanks for your help!

Not sure but if the circut is a switched ground you could have a short direct to ground.....
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post #6 of 8 (permalink) Old Apr 11th, 2008, 4:33 am
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I can only offer 2 cents from what I know of the KRS pump. The pump only has 2 wires so I've always assumed that it's 'cut-off' is done inside the pump when the pump reaches a preset pressure higher than the output rail pressure. I've never seen any wiring or an electronic pressure sensor outside the pump. It's max pressure feeding the injectors, is controlled by the regulator in the fuel rail at around 50psi.

4 things spring to mind:

1. Is the pump filter or pickup strainer blocked?

2. Is the fuel rail actually reaching the spec. pressure (check with pressure guage). If this mechanical regulator is faulty and bypassing fuel, the pump would run for ever.

3. If the fuel pump was faulty and not reaching pressure to cut out, it would also run for ever.

4. If the pump internal over pressure cutout had failed, it might try to run continuously.

I assume the hoses to and from the fuel rail haven't been messed with and swapped over.

Do a pressure test, if it comes up with the stable spec. pressure and the pump still runs I'd go for the internal pressure cut out being faulty (It's probably sealed inside the pump). If the pressure is low, then that sounds like a faulty pump seal or fuel rail regulator.



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Last edited by voxmagna; Apr 11th, 2008 at 4:40 am.
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post #7 of 8 (permalink) Old Apr 11th, 2008, 4:26 pm
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Quote:
Originally Posted by voxmagna
I can only offer 2 cents from what I know of the KRS pump. The pump only has 2 wires so I've always assumed that it's 'cut-off' is done inside the pump when the pump reaches a preset pressure higher than the output rail pressure. I've never seen any wiring or an electronic pressure sensor outside the pump. It's max pressure feeding the injectors, is controlled by the regulator in the fuel rail at around 50psi.

4 things spring to mind:

1. Is the pump filter or pickup strainer blocked?

2. Is the fuel rail actually reaching the spec. pressure (check with pressure guage). If this mechanical regulator is faulty and bypassing fuel, the pump would run for ever.

3. If the fuel pump was faulty and not reaching pressure to cut out, it would also run for ever.

4. If the pump internal over pressure cutout had failed, it might try to run continuously.

I assume the hoses to and from the fuel rail haven't been messed with and swapped over.

Do a pressure test, if it comes up with the stable spec. pressure and the pump still runs I'd go for the internal pressure cut out being faulty (It's probably sealed inside the pump). If the pressure is low, then that sounds like a faulty pump seal or fuel rail regulator.


But it should still shut off when the key is off.....
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post #8 of 8 (permalink) Old May 29th, 2008, 11:14 pm
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Ray is spot on , Same thing happened to my 87 K75s. Took me 5 minutes to fix when this happened. Disconnected the battery gave the relay a few good whacks. If it's fused beyond that... you may need a new relay.

Bill
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