Fuel system air leak

[rebar]

My Vgas bike runs fine after I purge the air from high spot in the tubing after the pump. But after a 1 hour ride, my clear fuel filter after my pump and air purge tee is almost empty yet I don't have a fuel leak.:ummm:

My first step will be to replace the fuel tubing from the tank to the pump, but I did check that out by pulling by mouth and didn't see any bubbles. But Im wondering if anyone has had a issue like that.. I did have the carbs off during last winter before this problem started. But it started right up in the spring.

Any ideas?

Oh BTW.. I haven't had my Vgas out to much this summer but just took it for a spin..unk: I love that bike..unk:

 

[alorio1]

I would check your tank vent for blockage and the tip over valve to see if its working right.

 

[dannymax]

I may be way out in left field but, was it a really hot day....is this maybe vapor lock?

 

[rebar]

I may be way out in left field but, was it a really hot day....is this maybe vapor lock?

Thanks

It was about 80 or more. Isnt vapor lock carb related? Could that allow air back into my fuel system?

 

[Thevmaxrider]

Vapor lock is usually associated with the fuel pump. I would guess that what is happening is the fuel in flowing back into the tank causing you to see air in the filter (I am assuming that your filter is before the pump) and you just happen to see it with the clear filter housing. I have a clear filter housing as well and have seen the same thing. As long as the pump keeps the bowls full you are in good shape and there is nothing to worry about.

 

[dannymax]

Thanks

It was about 80 or more. Isnt vapor lock carb related? Could that allow air back into my fuel system?

I really don't know how or where vapor lock shows up....just thought, with all the stupid hot weather around it might be a possibility.

 

[Thevmaxrider]

I really don't know how or where vapor lock shows up....just thought, with all the stupid hot weather around it might be a possibility.

On the VMax a prime cause of vapor lock is removing the plastic heat deflector off of the rear head. This allows the heat from the rear headers to flow directly onto the fuel pump and inlet line. Vapor lock is when the fuel in the line vaporizes prior to or in the pump. When this happens the pump will not pump enough fuel, if any, and your bowls run dry. As long as the bike runs fine and the fuel pump is filling the bowls I wouldn't worry too much.

Missed the part in his post that his fuel filter is after the pump. Still think that as long as the bike runs fine it isn't a big issue.

 

[tugla]

can install a one way check valve to help keep pump primed, or anywhere in the system to keep some fuel in if its running back.

 

[rebar]

I have two fuel filters.. One before the aftermarket pump and one after. Its the last one I see go almost dry because the first isn't see through or easily seen under the seat. Whats strange, is that after returning from a 30 minute ride the after clear filter looks almost dry. Then the next time I ride its full again.:ummm:

I don't have a heat deflector and run a kerker header.

Then tonight.. Much cooler.. Filter was still full after the same ride. :confused2:

Must be the heat vaporizing the fuel, huh.. I don't like this much because I don't trust the bike on a long ride.

Here's a few dirty pics.

 

[dannymax]

Try wrapping some aluminum foil around the fuel line and filters, see what that does.

 

[tugla]

is that a bleed valve the brass unit in the second pic? and take it your running a smaller filter in the first pic? looks different then the stock set up for some reason? is that chg when you run vgas?

 

[rebar]

is that a bleed valve the brass unit in the second pic? and take it your running a smaller filter in the first pic? looks different then the stock set up for some reason? is that chg when you run vgas?

Yes bleed valve. Its a shrader valve brazed on a brass barbed connector. Both pics are same bike. Two filters.. One before the fuel pump and the other after.

This is the fuel pump the PO had installed.
http://www.amazon.com/Mr-Gasket-12S-Micro-Electric/dp/B000BWCERY

 

[tugla]

dude thats a copy of a tyco pump i think its called, they are garbage and could be your issue, they are used on efi skidoos like my rt1000 and are the first things to fail and common mistake is replacing them with the same units. they are about 50-70 bucks, but a way better solution is a typical electric pump used on diesel gmc trucks in the 90's. ill find you the part number, they are a little cheaper, but way way better.

 

[rebar]

dude thats a copy of a tyco pump i think its called, they are garbage and could be your issue, they are used on efi skidoos like my rt1000 and are the first things to fail and common mistake is replacing them with the same units. they are about 50-70 bucks, but a way better solution is a typical electric pump used on diesel gmc trucks in the 90's. ill find you the part number, they are a little cheaper, but way way better.

Yea Iv heard they junk out quick. But for the moment, mines pumping just fine. From what I remember.. The Vmax pump turns on only when the bike is powered up. After that, the carbs pull the fuel once primmed. Unless the pump had a air leak on the suction side. It shouldn't be the issue. No pump can displace air or vapor thats trapped in the fuel line. Like my manual purge valve can.

But I wouldn't mind a stock pump but cant bring myself to spend that if mines currently working.

 

[tugla]

im sure someone will correct me but think it still runs as the float level goes down, when you put it to res it turns on pump all the time, so thats what i was to believe. anywho why run the filter? how about a one way check valve to hold fuel up in the filter?

 

[rebar]

anywho why run the filter? how about a one way check valve to hold fuel up in the filter?

I just returned from another run with half the filter empty again. 78 degrees out.
I agree. I will remove the second filter and hope the first does the job. Im guessing the fuel velocity slows in the second filter allowing it to warm up more. Straight shot should be keep it cooler.

Never had this issue last season though.

 

[alorio1]

My thoughts are, you should have a full line
of fuel to the fuel pump just like you were drinking a soda with a clear straw. I would check the fuel pump diaphragms (2) located within the pump itself. One of the diaphragms in the pump, could actually be a check valve, it seems logical to me anyway. This is a C&P from a thread Sean mentions the diaphragms I am referring to.


The pump is designed to run under a few conditions.

1. There must be power (duh). There is forced on power for 5 seconds when the key (or kill switch) is first turned on. This activates the timer/relay. If the bike is not running (with a signal from one of the cylinders) then the relay shuts off and shuts off power to the pump. This is one of those things to help prevent fuel from being pumped in a crash condition.

2. Once there is power it will only run until it reaches operating pressure. So, lets say you let the bike sit for an extended period (a few days is enough sometimes) or you just got done rebuilding the carbs. The pump will run fast for the entire 5 seconds as it's trying to fill the blows and reach pressure. In the case of a carb rebuild it will do this a number of cycles (turning the key off and on) until it fills and reaches pressure.

Once the bike has been started and or the bowls filled and line pressure achieved the pump will not run again until some fuel has been used or pressure relieved (by a possible leaking diaphragm). So, the next time you shut off the bike and or restart it within a short period of time the pump will maybe only click once, twice, or none at all.

If the pump continually runs all the time or never slows down and stops, then it's not building pressure. This could be an air leak at one of the hoses, filter, stuck float, stuck or bad needle, or simply a worn out pump. Sometimes the small diaphragms internal to the pump become displaced and then it can't hold pressure. Much like there are two valves to each half of your heart there are two for the pump.

We've seen pumps that appear to be fine but exhibit the symptoms you are describing. Sometimes they don't effect the performance and sometimes they do.

Hopefully this will clear things up a bit.
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[alorio1]

C&P from another site, but somthing to check:

I found a vacuum leak by removing the whole fuel line from the tank to the fuel pump, including the fuel filter. Put the whole fuel line in a bucket of water, cover one end with your finger and then blow into the other end of the line and look for air bubbles. I found a leak in the aftermarket fuel fiter that I was using.

 

[rebar]

I finally replaced all the fuel line and the pump which cured all my problems.

Not sure if I had a leak or the pump was bad. Don't care because it runs hard again and I can put it away for the winter knowing spring will be calling me.