Replace high-pressure fuel pump in VST and now fuel pouring out at the ….

[jkscarab]

check valve.JPG

permatex.JPG

I finally received my VST check valves and wanted to confirm the best thread application is Permatex #2 or is there something better for a fuel line threaded connection?
Teflon is discussed but it seems the teflon tape can rip on installation and little bits of tape can get where they are not suppose to be and hence the liquid Permatex.

Thanks for your help!!

[DewRonInc]

I always use a high quality thread sealant myself....

[JOE54]

is what i use , no silicone

[jkscarab]

Thank you @JOE54 and DewRonInc.

[SilverFox579]

I always use a high quality thread sealant myself....

+2!

[jkscarab]

remove both small hoses on top of vst float is either stuck ,bad or inlet has debri causing it to flood do not start this engine until problem is found you need to drain air plenum of fuel with engine tilted full up , also you may have pumped enough fuel in engine to flood oil res in boat with fuel diluting oil in res ,and hydraulic locking #5 and #6 cyls , be very careful dangerous situation there

So I finally received my parts (oil check valve at bottom of VST) and took the VST apart per JOE54 instructions to look for cause of why VST float is stuck down (not floating and shutting off the needle valve) and flooding the engine.

After I took apart VST Observation: The float valve worked freely up and down with zero friction (played with it a dozen times and no way it is "sticking". Furthermore the float when pushed up manually would bottom out parallel to the VST housing indicating there is nothing significant holding up the float. I did not take the needle valve out today (as it was hyper windy and didnt want to lose that little wire formed clip). I am hoping for a better day tomorrow. In the meantime, I am hoping to understand a bit more as it seems my flooding may not be the stuck down float as first thought.

Attached pic----
In an effort to understand the "fuel flooding into bottom of air plenum" ="stuck needle valve open" I marked up the fuel flow page from the service manual.

If I understand correctly the fuel I am entering into the system at arrow 1 from primer squeeze follows the fuel flow in the red numbers 1>2>3>4>5>6>7 fuel emptying out at arrow 7.

QUESTION: As the first solution was to ensure the float/needle valve was not hindered and prevented from closing seems unlikely from my observations listed above (needle moved very smoothly up/down and the float was dead parallel to the vst top housing (indicating nothing much could be in the needle/seat union. IS THERE ANOTHER PATH THE FUEL COULD TAKE TO FLOOD THE BOTTOM OF PLENUM? IF NOT i GUESS IT REALLY MUST BE THE NEED VALVE SEAT INTERFACE?

Sorry about the wordy message and goofy image but Im keeping these engines for awhile and am hoping to understand this failure mode.
Big thanks to all who have helped me this far. Hopefully I am almost "there/fixed".

[lpugh]

That is float drop adjustment, if to low the needle will hang to the side not allowing the needle to close. Easy to check, Spec is in the service manual

[JOE54]

its possible inlet needle was skewed upon reassembly of vst , seen this several times , if you had fuel coming out of small hoses on top of vst as i asked in #2 seat was not closed/leaking ,as per serv manual 822900R3 DO NOT attempt to bend float arm to adjust float height . float height is preset at factory . page 3c-46 fuel system

[EuropeanAM]

jkscarab: Please DO NOT POST AGAIN until you have read the Forum Announcements and your PM's.

I'm going to suggest you snap a picture of YOUR FLOAT, focusing on the tang that contacts the needle. Specifically want to see the surface that is in contact with the needle when it closes.

Any dimple, wear or abnormality in this surface will result in leakage regardless of how your float is "set". If there is a mark that you can "feel" with your fingernail or a sharp #2 pencil, REPLACE THE NEEDLE AND FLOAT.

There is plenty of top-quality help here on THIS forum. Don't confuse things with other people/engines/sites.

[jkscarab]

The attached pics show the VST float and needle just removed from the VST.
Observations:

1. There was a visible white ring around the needle which just wiped off with a fingernail. The Surface of the needle tip shows no apparent wear as the surface looks perfectly conical. I assume the oxidation on the needle looks like it “could be “ the culprit” to my needle/seat not shutting off properly and allowing fuel to flow past when the float is in the up/floating position.

1. The metal surface of the float that the needle rides against looks oxidized but the surface itself looks perfectly flat (zero indention into the base metal etc).

Questions:

1. Is it clear to those who have experienced this issue that the white ring (oxidation) on the needle is sufficient to prohibit the needle/seat from sealing properly?
2. As the metal surface of the float the needle rides against is oxidized but visually perfectly flat combined with new floats NOT being manufactured suggests just “polishing” that metal surface on float. Considering “polishing” with something like pencil eraser or 1,000 grit sandpaper? I am hesitant to use a solvent as the solvent might attack the plastic float. Or no worries sparying float-just shoot it with carb cleaner?
3. I could not get a decent pic of the mating/seat surface that the needle shuts off to. I assume some kinda solvent spray (carb cleaner) in that location makes sense?

Next steps? :
New needle assembly and how best to deal with float metal surface oxidation?
just removed from VST.jpgneedlecloseup.jpgcloseupfloat.jpg

[FeFanatic]

Yes, the oxidation could cause the needle and seat to malfunction. My concern is that it's not just the needle and seat but the whole system. You had to have a lot of moisture in there to do that kind of corrosion damage. Is that tab the base of the needle rests on weak and able to bend under pressure? What's the rest of the inside of the vst look like?

[jkscarab]

FeFanatic thanks for the reply. I will respond to your questions in the order asked.

Question 1: You had to have a lot of moisture in there to do that kind of corrosion damage.
ANSWER: The boat sat for 2 years but I always use non-ethanol fuel and have zero water in my gas/water separator (Racor filters).

Question 2: Is that tab the base of the needle rests on weak and able to bend under pressure?
ANSWER: the tab is very robust absolutely cannot bend under pressure. I agree the pics look bad but its just surface oxidation. I am a mechanical engineer by trade and understand your queston. I believe the float is robust once it is cleaned/maintained.

Question 3: What's the rest of the inside of the vst look like?
Answer: I took the VST apart to replace the dead high pressure pump. The pump looked used but nothing strange. There was no oxidation or anything in the VST bottom housing. Looked clean. The high pressure pump filter looked pretty used too...small particles on outside of filter.

Next steps:
Your Statement: My concern is that it's not just the needle and seat but the whole system.
Question: What else should I look at to maintain etc??

>>How best to clean up the operating surface (needle contact) on the float??

[lpugh]

easy to test sealing hold upside down so float closes needle valve and pump the primer bulb. Then upright gently raise the float up and watching the needle valve for free movement and that it does want to hang with float hanging down
Float system is very delicate, be careful.

[jkscarab]

EuropeanAM I ordered the Float Valve Assembly from your partner site. Small ticket item but im sure more to come. Take a peek at the float attached. 5 swipes of 1,000 grit got it looking a lot better. There appears to be a circular depression or something where the needle sits. Its perfectly flat there as I run over the surface with a pencil etc. Its just an optical thing....
Thanks for your thoughts/help.
float 1000grit.jpgclean receipt.JPG

[JOE54]

ANSWER: The boat sat for 2 years

Next steps:
Your Statement: My concern is that it's not just the needle and seat but the whole system.
Question: What else should I look at to maintain "" [ anything associated with the fuel system from the tank to the injectors including the injectors ..... NON ethanol fuel wont save it set up that long

[jkscarab]

Hey Joe54, Thanks for your advice to check the rest of the system including injectors etc. I am hoping to run the thing and clear the system out once I solve this VST issue. Is it your opinion that the white ring on the needle (pics above) is the "culprit" holding the needle from sealing properly leading fuel to flood over the VST? Thanks for your help!!!

[lpugh]

Possible, not likely. If it passes the tests I listed earlier, leave it alone as you could very well add new problems.

[jkscarab]

Ipugh, thanks for the additional detail. You wrote "Possible, not likely. If it passes the tests I listed earlier, leave it alone as you could very well add new problems."

Question: The test you are referring to is to turn the VST upside down (VST float up) and pump up the primer bulb to the VST fuel intake and see if the needle shuts off properly? that was the only test I thought I saw. i have ordered a new vst float kit and will perform this test for sure.

Im a little bit confused that you wrote "possible/not likely" if it is not the VST float/seat letting fuel flood the VST =>getting fuel into the air plenum etc. WHERE ELSE could fuel come from that would have the symptom of gas in the plenum etc???

[lpugh]

Imspect the needle valve closely right side up float hanging, gently move float up and watching the needle valve to sure it allways move back up perfectly everytime, sometime they will hang when lifted if float drop is to low, this is a very importent setting.
Mercury seems to think no one has skills to adjust these, most dont. I get that, the alternitive is to replace everything. Having dealt with thousands of these systems I can set them pefectly in 10 mins or less. Both level and drop. Exactly the same as adjusting them on carburetors, most carbs need to be measured though. I can not explain this to you other than what I have allready said. would need to show you. I will say though if it checks out on those 2 steps it is not needle valve issue

Be sure float actually floats and is not too heavy with fuel saturation.
Shake it to see if there may fuel inside the float

[JOE54]

make absolutely sure the bore of the seat and the seat itself is pristine so the needle slides up and down perfectly ,if it hangs part way it'll flood again easily tested with primer bulb inverted , you wont even be able to blow through it inverted from hose inlet ,get it clean all of it