Another DF115 VST Thread

[Aussie Angler]

Ahoy there,
I’ve been lurking for a couple of days, soaking up as much information as I can. Believe me, my home mechanic skills are very limited, I need all the help I can get.
I’m getting ready to remove and clean out the VST on my 03 zuke DF 115, I am picking up the shaped o ring seal/gasket to reattach when I have cleaned out the tank and the screen filter.
In the manual it says to use “Suzuki bond” when joining the 2 halves of the VST back together, which I believe is a “gasket maker “ type adhesive sealant. It is meant to be applied to the joining surface but should not contact the o ring.
Every report I have read (on this and other forums) does not mention this step.
There is a chance I will have to remove the VST again to replace parts if the clean out is unsuccessful so should I use this product or just rely on the o ring seal?
Thanks for any advice anyone can offer.

[Murray]

I would have some sort of gasket sealant (safe for fuel) on hand. Once you disassemble the VST you will see if the last person/factory applied sealant. My service manual calls for sealant on the lower unit (water pump) yet when I replaced the water pump there was no sealant from the factory so I followed their lead and didn’t apply any sealant.

[tsturm]

New "O" ring & clean surfaces & no Sealant ever.

[Aussie Angler]

Thanks for the advice, I’ll see what it looks like when I open it up

[Aussie Angler]

Well I’m devastated now, I’ve read so many horror stories about dirty fuel clogging up the vapor separator that I had convinced myself that was the problem.
I got the VST out, *** there was so much crap in there I cannot believe any fuel was getting through. The whole tank was full of filthy muddy fuel. The little screen filter was solid, none of the mesh was visible. The fuel regulator was invisible, buried under black stuff like tar.
i got everything cleaned up, the regulator opened at 37 psi so I didn’t replace it, the float switch mechanism looked ok so it stayed as well. I had purchased a Kemso hp fuel pump based on the fact that it was sold as “manufactured in Japan”
It turns out they are made in .... well you all know where,, I should have known better, 50 bucks? stupid me.
So I put the original pump back in, it really is made in Japan. New o ring, new hp fuel filter and new pump filter screen and all back together.
She fired right up 1st time and ran great for 5 or 10 minutes.... I thought I had nailed it..... then she died on me.
So I guess it’s going in to the Suzuki dealer in the New Year, at least I have a cleaned out VST and I have done a full service including lower gear oil and impeller.

Anyone have any thoughts as to what’s wrong? Electrical maybe? Just seems to die when it gets up to temperature...

Merry Christmas to all on here, and all the best for the New Year.

[redlowrey]

You should have explained in a little more detail about your problem, you have not wasted your time with the vst, at least you know that's right, Where abouts in Australia are you I am in vic.
When you say die do you mean it stops, or does it splutter like it has running out of fuel.

[Aussie Angler]

Yeah mate it needed cleaning out. I was hoping that was the only issue, there was a problem with the underfloor fuel tank, it’s running on a remote tank for now, I plan to run it on a remote tank for a short time and then have the floor cut out and a new tank installed.
Yes, when I said it dies, it slows, then it stops. Plenty of fuel getting to it so that’s not the issue. I’m just up the road from you, in Cairns

[redlowrey]

They are a pretty basic engine so you should be able to sought it out with out going to a dealer, did you change both the high and low pressure filters. So what do you do to get it to start when it stops, do you have to wait till it cools down or do you squeeze the primmer a number of times till it gets hard, and when you say there is plenty of fuel getting to it do you mean at the fuel injector rail or the low pressure pump..
We will get it soughted I just need a bit of information.

[Aussie Angler]

The primer bulb is hard when it stops, that’s all I mean by plenty of fuel getting to it, the little lp filter is full of fuel. Both high and low pressure filters were changed.
I pulled the outlet off the Lp pump, loosened the bolts, blocked the outlet and squeezed the bulb (I think I read that somewhere.. ) it seems sound.
It runs great for a few minutes so I am assuming that both fuel pumps are ok....? I haven’t touched the injector rail, it runs smooth when it runs so they should be ok I guess?
When it runs it revs up in neutral just like it always did, I haven’t put the boat in the water for obvious reasons.
I should point out that until I serviced it and started this troubleshooting the boat sat idle for years.
You can probably tell I have limited mechanical skills, I only started doing the work myself because I couldn’t find a local mechanic who would return my calls ...
By the way, it’s only run once (today) since I cleaned out the VST. Going by last week, I reckon it will start up fine tomorrow so does that mean it is temperature related?

[MikeyOrange]

If you're running on muffs, then yes it may in all likelyhood be temperature related. Mine ('08 DF250) doesn't like to run on the muffs as the temperature will climb fairly consistently, and if it gets past a certain point will shut itself down. I usually just start it, let it run for a few minutes and then shut it down. Do you have a network display that shows temperature that can be monitored?

[MikeyOrange]

Fuel/Water separator cleaned out & filter element replaced? Any trash collecting there? Does the tank have a bunch of crud in it possibly?

[Aussie Angler]

Thanks for your replies Mikey.
I’m running it off a remote tank, brand new with fresh fuel. Replaced all the fuel filters including the fuel/water separator.
Yes I’m running it on muffs, was never a problem before, and the telltale is warm but not hot. The impeller is new and the telltale is ok so should be cooling ok?
It’s an ‘03 with analogue gauges so I can’t monitor the temperature. I’m wondering if there is a bad sensor somewhere.
I’ve done a full service and cleaned out the VST but I don’t have any diagnostic tools (or skills) so it may be time to take it to an expert.

[Aussie Angler]

OK so I did some tidying up while I wait for the dealer workshop to open on the 2nd. I have wired in a new bilge pump and permanently installed the new fuel/water separator, it was just hooked up temporarily before.
So, I’ve got one of those Yamaha 22 litre tanks with the 2 pin quick release. From there it goes through a pretty flimsy primer bulb to my Racor filter bowl assembly. Then to a much stronger primer bulb and on to the engine.
I thought I’d fire it up and time how long it took to die.
It doesn’t seem to like the soft cheapo primer bulb, so I kept squishing it and the motor just kept running. The “permanent” bulb (it’s brand new as are all fuel lines and filters) stayed hard throughout.
She just kept running, a little rough at times but it didn’t die this time.

I’m wondering if the LP pump is not working properly after all and is not pushing enough fuel to the VST. Is there a way to check it without any pressure testing equipment?

[tsturm]

Get rid of the primer bulb before the separator.

[Aussie Angler]

Cheers Tsturm,
Yep will do, it’s one of those cheap arse all in one hose, bulb, quick release things. I’ll get rid and see how she runs without it