Tips to Prime a New VST & Hi-Pressure Fuel Pump

[Old No7]

As follow-up to my post below about "BF130 Fuel Delivery Plus..." I will be installing a new VST and high-pressure fuel pump this coming weekend. Everything else in the fuel system checked out OK.

--> Are there any tips on how to prime it?

* Will pumping the bulb do that alone? (that would not fill my old one, as the float won't move)

* Should the key be "on" (not started) while pumping the bulb to fill the empty VST?

* And is it correct to "cycle the ignition on/off 25 times" (without starting) to fully pressurize the new pump?

I want to eliminate any air bubbles from preventing a good solid start, but for sure, there is air in the lines now.

Thanks in advance!

Old No7

[Alan Hicks]

You're over thinking this a bit I think. The fuel pump runs submerged in fuel within the VST. Use the primer pump until firm as usual, and the system should start right up for you as it would normally. No extra pumping or key cycling necessary.

[chawk_man]

Alan,

I'm not so sure of that. Although I've never had to do a fuel pump or VST replacement, and I don't know much about the 130, I don't see how the VST will fill up by itself. I would open up the VST drain and prime it until fuel came out of the VST drain. Then close that up and cycle the key switch a few times with that safety lanyard pulled.

[Alan Hicks]

I think of the VST as just a big float bowl (with float and needle/seat to control fuel level) that's vented and easily filled with the primer bulb. That's been my experience to date anyway.

I suppose if you were starting with a completely dry system (no fuel in the lines or fuel rail) it wouldn't hurt to pay a little more attention. There it may pay to cycle the key a couple of times, and see if the primer bulb could be pumped up a little more afterward.

Above based on my experience with the 50 to 90 hp fuelies. I suppose it's possible there maybe something unique to the bigger motors, but I don't see it in the parts break down.

[chawk_man]

Here is how the VST is described:

The VST is in place to ensure an adequate amount of non-turbulent fuel is available to the high-pressure fuel pump. The fuel in the VST tank is kept under pressure to prevent vaporization, thus preventing the fuel from becoming too lean under variable demand.

[Alan Hicks]

So when you open the drain on a VST, does the fuel come shooting out like it's being held under pressure, or does it dribble out, more like a carb being drained?

They may be referring to just the slightest pressure. Pressure low enough that it's easily overcome with the primer bulb for instance.

[chawk_man]

Normally, the fuel comes out in a steady flow, under low pressure. But that small opening at the drain set screw can easily get clogged. I think that the LP fuel pump normally provides the pressure to the VST. Although I know that when you activate the HP fuel pump there seems to be more pressure for draining the VST.

[Alan Hicks]

Maybe VERY low pressure?

Let's move on, agree to disagree if necessary. -Al

[Old No7]

FIXED IT -- the BF130 is up and running with a new VST & High Pressure pump!!

Not picking any sides, but it turns out CHawk was correct -- it took a little extra effort to fire it up.


After rechecking all the electrical and fuel line connections to the new VST/HP Pump, I pumped the bulb maybe 25 times, ran the "switch on" cycle several times to pressurize the tank, and then I had my wife try to start it as I pumped the bulb...

...nothing...

..uh on -- not the result we wanted...

So I pumped the bulb maybe 20 more times; then tilted the motor up and opened the VST drain and some fuel drained out; so I pumped the bulb a few more times to see that with each pump, more fuel came out the drain.

Then I lowered the motor, and while I thought about grabbing my wife's stethoscope (as she is a Medical Assistant), I literally put my ear up against the new VST and listened to hear fuel trickling into the VST with each squeeze of the bulb. Rather than fast pumps, I slowly squeezed the bulb, kept it squeezed for a second or two, and then released it and did it again -- maybe 25 more times. I don't know whether it was full or not, but I could hear that it had more fuel (by the way it sounded as it filled).

Then I disconnected the safety lanyard and hit the starter -- leaving the switch "on" -- and by doing this, the high pressure pump runs for more than the 2 seconds as it typically does at startup. I let it sit pressurizing for maybe 30 seconds. After that, I reconnected the safety lanyard, and instead of having the neutral throttle lever halfway up -- I went for broke, and held it all the way up and hit the starter --

...and VROOM she started up!

She sounded great and had a great pee stream (much better than mine, but I'm 40 years older than the motor...) so I let her run for another 15 minutes or so. Several times I advanced the throttle while looking for signs of any fuel leaks, and all is well.

It turns out that Honda of South Georgia (FAST shipping by the way!) not only sent me the new VST & High Pressure Pump -- I also got a new fuel rail and EVERY fuel line from the fuel rail to the VST/Pump, back to the onboard Fuel/Water Separator -- with a new one of those too -- and the curly lines to the low pressure fuel filter. That latter piece wasn't included, but mine LP filter is new anyhow. Plus they included new o-rings, screws and fuel line clips. I will replace all the 20 year old fuel lines some other day -- as I guess I was too eager to get it going today.

Am now planning to go fishing tomorrow!!!

I hope this helps someone else.

Old No7

[chawk_man]

Glad it's fixed. Perseverance pays!

Where are you fishing?