Belly tank pump leaks.

[MarkT]

Having a drain-down problem with my setup.  Have isolated it to the fuel pump.  Measured it, leaks the entire 3 gallons to fill the belly tank in 19 hours.  That's a tablespoon (0.5oz) every 89 seconds.  If I pump up my belly tank contents - 2 hours later it takes 61 seconds to pump back up what leaked down. (It takes 9:35 to pump up the entire 3 gal. ) Significant leak.  Way more than needed to cause hydrolock.  So don't assume your belly tank will prevent hydrolock - you still have gravity pressure pushing gas through your system - install a Dan-Marc anyway.

Caveat - this leak is in the opposite direction of what would be needed to cause hydrolock for your standard install.  If they have a check valve (one way) inside the pump, it has to be in the direction of normal output, and it's leaking with back pressure.  If there's no mechanism to stop forward flow when it's off - it's not protecting you.

Another caveat - this is measured on my system only.  Statistically insignificant. Maybe my pump has a problem.

I'm installing a check valve in the line in mine. Next week, after the Darby ride.  I'd say a Dan-Marc is the preventive measure for the rest of you. (I already have a D-M.)

Word to the wise - this is perhaps bad news but it's from empirical measurement - don't shoot the messenger.

[bentwrench]

Mark,
            I'm interested in this problem,but I'm confused about where exactly is the fuel going?
My belly tank has worked fine for 80k since I installed a heat shield for the fuel pump.
BW

[DarkSideR]

Mark,
            I'm interested in this problem,but I'm confused about where exactly is the fuel going?
My belly tank has worked fine for 80k since I installed a heat shield for the fuel pump.
BW

He uses the belly tank as a reserve tank. Though not typical he can have gas in the main tank, while the belly tank is empty. With this in mind re-read his post and it will all make sense.

[MarkT]

I detailed the install here. http://www.valkyrieforum.com/bbs/index.php/topic,84264.msg829542.html#msg829542

It was involved to work the bugs out but it works great now.  Except I want to stop the leak-down backwards thru the pump.

[mark81]

did an engine swap on a Suzuki samurai. new electric fuel pump on frame rail since no longer had mechanical pump on block. after a few hours the entire fuel line would drain back into tank and pump would lose its prime. burnt up a few before installing check valve at the tank.  check valve was purchased from summit racing or jegs, can't remember which.

[MarkT]

Installed a check valve like this, in the fuel pump line.  No more leakdown.

[Rams]

Mark,
            I'm interested in this problem,but I'm confused about where exactly is the fuel going?
My belly tank has worked fine for 80k since I installed a heat shield for the fuel pump.
BW

He uses the belly tank as a reserve tank. Though not typical he can have gas in the main tank, while the belly tank is empty. With this in mind re-read his post and it will all make sense.

Now it makes sense to me.   Thanks for that information.