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Ok, changed my VST filter weeks ago and engine losing rpm and stalling stopped and ran great for about 5 outtings. Now, about 8 miles out after running and trolling for about for about 5 hrs its starts surging and dieing again.
Checked the VST filter and the new one I put in was covered with a gritty film. I also drained my water separator filter too. it had a couple of ounces of brownish water. not a lot. It's the same engine that has gas bought at the same time/place as the other. the other engine doesn't have this issue.
What kind of filter are you running? Is it a Racor? If not, get a Racor that filters down to 10 microns. I hear the newest Yamaha filters do so too, but anything else should be changed out.
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do I want the 10 micron on the VST filter (already stopping stuff so good I am losing flow) or the bulb filter upstream from the VST (currently some kind of paper deal)?
if you are talking about the screen on the end of the hi pressure pump. have you installed the late design with 3 x the screen area ? supposedly the fine material on the screen is coming from the pump wear and tear, get the late style filter and let her rip
late style? what is this? where do I get them? are you referring to the low-pressure pumps wear/tear? the high pressure pump is on the other side (from sediment) of the filter. how is the screen area 3 x larger? the canister portion of the vst tank is pretty small?
talking about the hi pressure electric pump that lives in vapor tank. the new filter for it has 3 x more screeen area. costs $100. smudge looking stuff on screen is bronze wear and tair from hi press pump
ok. Just bought a filter for it. cost me $104.50 each. how do i know what "late style" filter is? What is the brand, model name, etc? if the wear material is coming from the high pressure fuel pump, shouldn't I be focused on that?
Get yourself a Racor S3213. I had one occurance of that exact problem in the beginning. My issue was associated with crap in the fuel tank, during it's manufacturing process and making it past the orginal fuel water seperator, and clogging my VST filter. Once I went to a Racor s3213, the issue was resolved. Good Luck.
ok. Just bought a filter for it. cost me $104.50 each. how do i know what "late style" filter is? What is the brand, model name, etc? if the wear material is coming from the high pressure fuel pump, shouldn't I be focused on that?
I am having similar problems with one of my 150 HPDI's. What is this filter that you bought? I just bought one... It was yellow, Yamaha factory part 68F-13915-00 cost me $67.00 each. Havent' tested the boat out yet though.
on my model they are white. it is a filter that goes on the end of the high pressure pump. The one referred to above is a w/s filter, which I also purchased and installed.
The above poster is correct. When the VST filter gets clogged with fine black particles, it's from the high pressure pump itself. I believe it is a fine dust of carbon off of the brushes on the motor. It's usually an indication that the pump is about to fail. Clean the screen again and replace the pump. Problem solved.....
ok. I have no problem with the replacement. However I do have a question. The VST filter fits onto the bottom of the pump which is th only "inlet" into the pump. the only "outlet" is on top of the pump and through the VST cover. If the pump is entirely sealed with the exception of the in/out-lets, how is brushing dust from inside the motor getting out into the tank and on the outside of the VST filter and sucked back in again? also, wouldn't any dust from inside the pump be more likely to be pumped out of the pump with the fuel instead of out into the tank? Wouldn't this mean that some of the fuel sucked in through the filter is being pumped back into the VST tank as well?
On the 0X66 models, the high-pressure pump intentionally supplies more fuel than the injectors can handle, and the excess comes back into the VST via the pressure regulator.
HPDI's have 3 fuel pumps. First , fuel is pumped into the VST by a set of diaphragm pumps just like what fed the float bowls in carburetors for years. In fact the VST can be thought of as a sort of carburetor float bowl complete with a float that regulates the amount of gas in it.
Inside the VST is an electric fuel pump [not high pressure] that feeds the final high pressure pump that is belt driven and located on the upper rear part of the engine. This is what feeds the injectors.
As for filters- the gas is filtered before going into the VST by a water separating filter on the left side of the engine. There is also the filter screen in the pick up of the electric pump in the VST. And finally- there is a D cell battery size filter between the electric pump and the high pressure pump.
If you see black particles in the VST, I would start thinking diaphragm pump.
What is the best way to test and diagnose which pump is going bad? I am tired, and going broke replacing parts attempting to diagnose problems. On my starboard motor I just changed the screen on the bottom of the pump inside the VST. The screen was clogged and gray. I tried using compreessed air & some solvents, but was not able to get it all out and then spent the money ($98.00) for a new screen and O-ring. What is my next move? I can't afford to start replacing fuel pumps that don't necessarily need to be replaced. Thanks for all the help.
HollywoodFish - 5/26/2006 10:48 PM
but was not able to get it all out and then spent the money ($98.00) for a new screen and O-ring. What is my next move? I can't afford to start replacing fuel pumps that don't necessarily need to be replaced.
Welcome to the world of Yamaha. There are also addtional $90 filters on each motor that should be changed at 100 hr. intervals. They are the ones between the VST and the belt driven high pressure pump. Be sure to change the paper engine filters at 100 hour intervals, too. They are only about $30 apiece. If left too long, the paper starts to come apart and can be found as lint inside the VST and plugging up the electric fuel pump screen.
gray or black debris can also be the insides of the fuel hoses deteriorating.
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What is my next move? I can't afford to start replacing fuel pumps that don't necessarily need to be replaced. Thanks for all the help.
Go out and make a small investment in some fuel system troubleshooting tools. A fuel pressure gauge($30-40), vaccum gauge($15) and some misc small fittings to tee the vac gaugethat into your fuel system before the engines fuel filter. Also a small psi gauge that will read less then 10 psi so you can tee that into the hose coming out of the fuel pumps that go into the VST tank. With those gauges you will be able to determine if the engine is having trouble getting fuel (vaccum high or low), delivering fuel from the pumpsto the VST(small pressure gauge) and if the VST pump is providing adequate fuel to the high pressure fuel pump(with the $30fuel pressure gauge).
All of these tools will be able to be used on any fuel injected outboard.......any brand. Also I have a Yamaha pdf that has some great fuel system troubleshooting info on it. parts@shipyardisland.com
If your engines have 300 or more hours on them, you are not wasting your money by replacing the mechanical suction fuel pumps. At $30-$35 a pop......... its good preventative maintenance.
Andy
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VST Filter again? 
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