Automatic Fuel Valve


Information and questions on GL1500 Goldwings (1988-2000)
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Shiny
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1988 GL1500

Automatic Fuel Valve

Postby Shiny » Sat Mar 29, 2014 1:24 pm



Should there be enough vacuum in the engine when cranking over to open the automatic fuel valve?



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Shiny
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1988 GL1500

Re: Automatic Fuel Valve

Postby Shiny » Sat Mar 29, 2014 2:37 pm

Never mind - curiosity got the best of me so I pulled the valve off and opened it up - sure enough, the diaphragm had a hole in it. Looks like time to rebuild it.

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redial
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Re: Automatic Fuel Valve

Postby redial » Sat Mar 29, 2014 8:25 pm

Curiosity is a great tool! It takes you places that you are sometimes not equipped for, but you will have fun along the way - usually.
Len in Kapunda

The world is not going to finish today, as it is already tomorrow in Australia and New Zealand, and other islands of foreign nations such as Guam and Samoa.

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ct1500
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Re: Automatic Fuel Valve

Postby ct1500 » Sat Mar 29, 2014 9:45 pm

It is not so much the vacuum that opens the valve , it is the fuel pressure of pump that overcomes the spring of valve. If this were not to happen every guy that ran his 15 out of fuel or when it was new would have to put a vacuum pump on valve to open it to prime carbs.

Every 15 I have worked on will continue to idle after vacuum hose removed from auto fuel valve and is clear evidence fuel pressure is partially opening valve. When engine starts and good supply of vacuum present is when the valve opens completely.

The only time it is completely closed is engine off and no vacuum to valve which is the way it should be, to prevent fuel from entering engine when not running.

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thrasherg
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Re: Automatic Fuel Valve

Postby thrasherg » Sun Mar 30, 2014 9:53 am

ct1500 wrote:It is not so much the vacuum that opens the valve , it is the fuel pressure of pump that overcomes the spring of valve. If this were not to happen every guy that ran his 15 out of fuel or when it was new would have to put a vacuum pump on valve to open it to prime carbs.


For your first statement to be correct the fuel tap would have to be after the fuel pump? I believe the tap is before the pump, so I believe this answer to be incorrect. The vaccum pressure does overcome the pressure of the return spring causing the diaphragm to move and allowing fuel to flow. Someone please let me know if I am wrong? I have never seen a fuel tap be placed after the fuel pump.

Gary

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ct1500
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Re: Automatic Fuel Valve

Postby ct1500 » Sun Mar 30, 2014 3:00 pm

The fuel pumps for the 1500 are in tank, the only thing before the pump would be the pump pick-up sock, everything else in the fuel delivery system is after pump including the fuel valve. Fuel pump operation begins at point of pick-up.

There are 2 diaphragms of the auto fuel valve, one is for vacuum from intake manifold and the other is the actual fuel stopper part and are connected together via steel rod, when one moves so does the other. There is a spring in the valve to ensure closure of the fuel stopper part. Naturally when one applies vacuum to valve it will open stopper part to its maximum opening.

However because of the orientation of the stopper part of valve, fuel pressure with pump running is pushing against the stopper in an opening normal fuel flow direction. If the valve were designed the other way around which it could have been, in a closing direction of stopper shutting off fuel flow. One has to ask themselves why would Honda design it one way and not the other. Simple, to help prime carbs after a run out of fuel situation or when new leaving the factory.

Many have had vacuum diaphragm tears of fuel valve (technically rendering it inoperative) without a total no run engine as the normal fuel line pressure is acting against the stopper forcing open slightly and working against the normal spring closure action.

This valve diaphragm here which is shot only ran out of fuel at highway speeds causing loss of power.
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thrasherg
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Re: Automatic Fuel Valve

Postby thrasherg » Sun Mar 30, 2014 4:46 pm

I stand corrected, thanks for explaining. I have not come across a bike with a pump inside the gas tank before..

Gary

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baumedagn
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GL1800HPNM

Re: Automatic Fuel Valve

Postby baumedagn » Sun Mar 30, 2014 5:38 pm

If I'm not mistaken, the GL1800 fuel pump in in the tank also.

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thrasherg
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Re: Automatic Fuel Valve

Postby thrasherg » Mon Mar 31, 2014 11:51 am

baumedagn wrote:If I'm not mistaken, the GL1800 fuel pump in in the tank also.


I suspect any motorcycle with fuel injection will have a pump inside the gas tank, I have not had to work on a bike with fuel injection so far!! :lol: Just call me the dinosaur!!

Gary

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redial
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Re: Automatic Fuel Valve

Postby redial » Mon Mar 31, 2014 7:21 pm

Hello Dinosaur,
From the Sabre Toothed Tiger, lushing it out in the sunshine down here. I havent been able to get into one of those new fangled things, either, fuel injection - who needs it?


Len in Kapunda

The world is not going to finish today, as it is already tomorrow in Australia and New Zealand, and other islands of foreign nations such as Guam and Samoa.


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