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BF200 Leaking fuel from vapor separator

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Ridehrd

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BF200 with 350 hours. Fuel is leaking from overflow of vapor separator. Have already replaced needle valve and cover (valve seat).
 
William01 said:
Did you check/adjust float height to spec?
Click to expand...
I did, but I’ll pull the vapor separator to double check. I have a clarifying question. Manual says to measure distance between float and cover “at the tip of the float”. The drawing is confusing, because it’s not clear which tip is being measured. Closest to the needle valve? Furthest from the needle valve? Side of the float?
 
Manual says float height is to be 29-34 mm. It would seem measurement location could be critical.
The overflow problem seems to be happening after the engine is run for 30 minutes or so.
 
If you have the Helm shop manual, look at around page 5-88. In the picture, it specifically says to measure the height at the tip of the float.
 
It seems unusual that this problem would reveal itself after the engine is running for 30 minutes. Check your fuel pressure. Attach the pressure gauge where the fuel pressure relief bolt is located on top of the cover to the HP fuel filter. You will need a 6 mm adapter. Disconnect the vacuum line to the fuel pressure regulator and either clamp it or plug it. At idle (600 rpm +/-) fuel pressure should read between 41 and 48 PSI. See page 5-69.
 
Vapor separator overflow is on low pressure side of fuel supply. The relief bolt is on the high pressure side. Am I correct?
 
Just to describe the problem more clearly: The engine runs great. On initial start and idle, there is no evidence of leaking fuel. After running for about 30 minutes with engine speed around 4000 RPM or so, and docking at idle, a sheen appears in the water.
 
Low pressure fuel pump replaced about a year ago. Diaphragm failed, allowing fuel into engine oil. Could this pump be overpowering the closing pressure for the needle valve at higher RPM? Could temp of low pressure side of vapor separator be getting too high, causing pressure to rise in the reservoir? Water supply and return to water jacket of vapor separator are connected.
 
I'm trying to think through this issue.

I imagine that it is possible that the water jacket on the VST is not getting sufficient cooling water to keep it at ambient temperature. So check those water hoses and the inlet and exit nipples on the water jacket. Blow low pressure air through the intake nipple to make sure there are no obstructions inside.

Another possibility is that the fuel line cutoff valve is not working (i.e. staying engaged) allowing too much pressure to build up in the VST. See the following attachment.

Beyond that, I'm thinking that there is something amiss in the float or float valve inside the VST.
 

Attachments

  • Fuel line cutoff Solonoid Valve purpose.pdf
    511.9 KB · Views: 95
chawk_man said:
I'm trying to think through this issue.

I imagine that it is possible that the water jacket on the VST is not getting sufficient cooling water to keep it at ambient temperature. So check those water hoses and the inlet and exit nipples on the water jacket. Blow low pressure air through the intake nipple to make sure there are no obstructions inside.

Another possibility is that the fuel line cutoff valve is not working (i.e. staying engaged) allowing too much pressure to build up in the VST. See the following attachment.

Beyond that, I'm thinking that there is something amiss in the float or float valve inside the VST.
Click to expand...
Thanks for sticking with me on this!
I’ll check the water jacket and recheck float height.
Regarding the fuel cutoff solenoid, is there a good way to check that? Does this solenoid prevent fuel from going to the vapor separator with engine off? One thing I’ve noticed: with engine off, I can sometimes squeeze the primer bulb and cause fuel to overflow.
 
Take another look at the document I attached regarding the fuel cutoff valve. From what I understand from that, its normal state is closed, except under the conditions described. From that description, it looks like it is some sort of fuel bypass, allowing fuel to travel into the VST under those specific conditions in order to prevent vapor lock, possibly bypassing the function of the VST float valve. That is sheer speculation on my part. But if that is the case, then I would further speculate that if that valve has failed and is open constantly, then it could overload the amount of fuel in the VST chamber.

Hopefully, someone with more knowledge than I have about that valve will jump in.
 
Hi,
Just following along but, in my opinion, that solenoid valve hung open causing the overflow make perfect sense to me.

The document states that the longest time that the valve should be commanded open is 50 seconds.

So, if that valve is sticking open it is always delivering an unknown and unwanted amount of vapor pressure and possibly liquid fuel to the VST chamber since it is directly connected to the fuel pump.
That might very well cause the overflowing.

I believe that a valid test might be to simply pinch off the hose from the valve to the VST and run the engine to see if the overflowing stops.

Just keep in mind that in the event of hard restart you might need to remove the blockage.

Watching with interest.

Good luck.
 
Just to illustrate the plumbing.....

Here's a depiction of the cut off valve (item 6) and fuel pump (item 9)


Note that hose segment from pump to valve (item 10) appears to have an integral check valve.

The following link shows how the feed hose (again, item 10 in link above) connects to an alternate outlet at the top of the pump. Extreme left center of page inside dotted lines.


If you pinch off the hose from the cut off valve and the overflowing stops, you will then need to determine if the cut off valve is stuck open OR is being commanded to stay open. If it is being commanded to remain open then simply replacing the valve won't solve the problem.
 
Thanks chawk. You had a great idea that I was missing.

Now, to see if Ridehrd can fix this easily. I'm hoping it's just a stuck valve but you never know. If it isn't it gets a bit more complicated. Fingers X'd.
 
Thanks for the ideas, guys!
I checked the solenoid valve. It is not stuck open and continuity values are within spec. I have not checked yet to see if the valve is being commanded to stay open by the ECM.
I traced all of the vacuum and fuel lines and their connection to the vapor separator. I found the vacuum lines to the vacuum tank were swapped. One of them has a check valve in it, and being swapped prevented the vacuum tank from doing its job. One of these vacuum lines was also disconnected at the top of the intake manifold.
I also put a new float in the vapor separator. The needle valve and vapor separator cover (with valve seat) had previously been replaced.
I plan on testing the motor this afternoon or tomorrow. If it continues to leak, I'll get a pinch clamp and close off the hose from solenoid to low pressure fuel pump.
 
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