need help on vst problems on df140

[macksk8er]

I found that my 2005 df140 is pumping gas directly into the crankcase from the vst via the evap hose. I changed the needle valve and seat which seemed to fix it in the driveway. Took it out yesterday and idled fine to the lake and got up on plane fine. After sitting for a few hours off it did not want to restart. once it did, it died on me at idle. Would not restart. Got home and the oil is once again filled to the brim with gas. The vst is again pumping gas through the evap hose. Is there anything that would cause this other than the float or needle valve?

 

[montanabay]

Re: need help on vst problems on df140

maybe too much back pressure in the VST, maybe from a plugged screen or a plugged up high pressure filter, did you try changing that out?

you can take them off and pump mineral spirits through it quick, followed by clean gas, might help clean out anything block a passage and causing back pressure.

 

[macksk8er]

Re: need help on vst problems on df140

I replaced the high pressure filter and the screen on the bottom of the high pressure fuel pump. Brand new low pressure filter and racor also.

 

[montanabay]

Re: need help on vst problems on df140

hmm, wonder if the float switch is off spec or stuck, so the VST just keeps filling with gas until it over flows up the vent to the case.

double check the clearance on the float switch (might need mm calipers).

you might also want to replace the fuel pressure valve inside the VST, again if that baby is stuck it might allow pressure to build beyond spec and to over flow to the case.

worst comes to worst put a one way valve on that line

 

[Tcrum5711]

Re: need help on vst problems on df140

Had same problem for a long time. Actually had a thread going the last couple of weeks on here other than mine is a Zuki DT150. Mine ended up being where the seat screwed into the VST cap, there was a nick in the metal that the gasket wouldn't seal properly. I ended up fixing the nick and now it seals up. I should have ordered a new cap, but I wasn't willing to give up any more time on the water.

 

[macksk8er]

Re: need help on vst problems on df140

So I finally broke down and took my boat into a Suzuki shop about an hour and a half from here. After a week and a half they finally got back to me and said that the low pressure fuel pump is bad. I am no mechanic, but would this overflow the vst out the evap hose? I asked the mechanic this question and he was confused on what I meant by the evap hose. This is not very reassuring. He said it will be done on Friday. I am thinking i will have to launch from their marina and call him when I'm stuck on the water if it is not fixed right. Any thoughts?

 

[clanton]

Re: need help on vst problems on df140

The low pressure fuel pump can push fuel into the crankcase if the diaphram is bad.

 

[macksk8er]

Re: need help on vst problems on df140

I know that, but fuel was still coming out of the evap hose on the vst into the top of the crankcase. could a bad low pressure pump cause that? The mechanic didn't even know what I meant by and evap hose. When he first said the pump was bad I asked him if it was the high pressure pump or the low pressure pump. He didn't know and I had to explain to him which one was which before he said it was the low pressure pump. Again, not very comforting to hear.

 

[Tcrum5711]

Re: need help on vst problems on df140

I'm not real familiar with the DF series since I've got a 2 stroke Suzy, but doesn't the evap hose coming off the top of the vst tank go into the intake manifold? If it does, wouldn't that extra gas be burnt up eventually instead of going into the crankcase or cause a rich condition till it's burnt up? When I rebuilt both of my low pressure fuel pumps with new diaphragms, there was a small opening that ran to the cylinder that caused the diaphragm to move/pump. If your diaphragm is torn it could be getting fuel into the crankcase that way. A good number of these dealers/shops now are parts changers instead of mechanics. I dealt with a couple of dealers for the last 6 years trying to get mine to run right. Finally said that if they're going to charge me to change parts and not diagnose problems, I could do that myself.
Make sure where the seat screws into the VST cap is tight and holds pressure. That's where mine was leaking. Use two gaskets if you have to. I didn't see it until I filled the cap with water and blew through where the evap hose hooks on. Bubbles came up from around the seat itself.

 

[clanton]

Re: need help on vst problems on df140

The fuel level in the VST comes from the low pressure pump, level in VST controled by the float. The float and seat not working, or casting is bad allowing fuel to bypass the needle and seat. The fuel pressure regulator dumps fuel back into the VST. If the regulator or seal is leaking, VST would overflow.
Check the pressure on the evaporator hose, should be close to 0. The manual I`m looking at has fuzzy photo, but looks like the needle seat has a seal or o-ring on it. If this leaking float has no control over the fuel level.

 

[gblskl]

Re: need help on vst problems on df140

I have a dt 200 that has been leaking fuel into intake manifold.I bought new fuel regulator and vst and still leaking. I am checking fuel pumps today runs really bad and smokes will post if low pressure pump is bad.

 

[macksk8er]

Re: need help on vst problems on df140

I got the boat back on sat and took it out on sun. ran good, but at wot it seems to miss every once in a while. I talked to the mechanic about it and he told me to try changing my spark plugs. I did that today, so I am hoping that solves that problem. As for the vst, I checked the oil after a 4 hour trip and it is the same level as I started so I think I am in the clear. Guess it was the low pressure pump.