'03 DT150 VST Problem

[Tcrum5711]

Been having problems with start up on '03 DT 150. It'll idle perfectly and soon as you motor away from the dock at a higher rpm than idle, it'll start missing and acting up, blowing blue smoke until it cleans itself out. Figured it was getting too much fuel, i.e choking itself out even with the EFI. So, I replaced the VST needle, seat, o-ring, cap gasket and the fuel pressure regulator. I haven't ran it yet but searching back on prior VST problems of other posts, I found that the air vent line that goes back into the intake manifold on the top of the VST should not have any fuel in it and that a good way to check the needle and seat is to use the primer bulb and if any fuel comes out, its bad. Mine pumps fuel out this air vent line with brand new parts. Is this normal for this motor or should I disassemble it again, maybe bending the arm that the needle rides on to get a better seal? Any ideas or suggestions would be appreciated.

 

[Tcrum5711]

Re: '03 DT150 VST Problem

Bump

 

[rodbolt]

Re: '03 DT150 VST Problem

if you have raw fuel in the intake vacum line then the needle assy still has a leak someplace or the float adjustment is incorrect.

 

[macksk8er]

Re: '03 DT150 VST Problem

Let me know what you find out on this. I am having rough idle problems and had my engine stall out on me after a long run and not start for an hour. I have since changed the primer ball and noticed that I get a lot of gas that is going through that line into the top of the crankcase when I pump the ball. I believe in the manual they call it an evaporation line. I am wondering if the float and needle valve are messed up and flooding the engine. I have a df140.

 

[dawelder]

Re: '03 DT150 VST Problem

thats the same problem im having ,i took the needle out and it looks like there is a line or ring going around it like where it seats . the needle is 55 dollars and having to order one if that is the problem, or the float needs adjustment.I never had my injectors cleaned but have cleaned the filters and put new ones in.Could the injectors not spray enough cause the vst to load up. 2001 f115 4 stroke first problem since I owend the motor. 9 years thanks joe

 

[Tcrum5711]

Re: '03 DT150 VST Problem

In theory the needle should seal off the tank to not allow any fuel in. I didn't see any ring on my original needle, but I've replaced it with new parts and it still pumps fuel into the air vent line that goes into the manifold. I ordered and new set of floats a week ago Saturday. Hopefully they will be in the start of the week so I can test it out. It'll hold pressure upside down with all the fittings plugged though. I'm thinking that adjusting the float arm and new floats will help.

 

[Tcrum5711]

Re: '03 DT150 VST Problem

Tested today with the new floats and adjusted the arm a little. Let it run in the drive way and pulled the vent hose hose off. Still having gas coming out the vent line that goes into the intake. Guess I'll take it apart one more time and use water to see if the needle even goes up far enough to seal the tank. Gas is getting to expensive and the garage is really starting to smell like a gas can.

 

[Tcrum5711]

Re: '03 DT150 VST Problem

For you guys looking for what ended up fixing the problem, I think I finally tracked it down. Looks like there was a nick in the metal in the VST top that didn't allow the gasket to seal all the way. I took it apart for the tenth or so time and blew through it without the needle in with my finger over the seat and heard fizzing. Fixed the nick, put it back together and no more leak from the intake vent. Going to lake test hopefully this week. Looks like it's better to be lucky than good.

 

[99yam40]

Re: '03 DT150 VST Problem

Good to hear it is fixed, makes sense if you think about it how that would effect it.