Resolving Vapor Lock Issue-2007 DF200

[Lostsoul58]

Risk = likelihood x consequences.

Likelihood of a fuel related/fuelled fire in a situation where the ignition key CANNOT be turned off?? Add in the unlikely presence of an ignition source with a pump installed under the gunwales away from the engine heat? Negligible. Score = 0

Consequences: any fuel related fire has bad consequences. Score 9

Likelihood 0 x 9 = 0. Risk rating: Very low to negligible.

Even the engine's own low pressure fuel pump is running whenever the key is turned on. So the added risk of installing the separate pump is very little extra from what already exists.

Dont make this overcomplicated or imagine risks that arent there.

At least on my engine the low pressure pump is running only when needed, not wired to run all the time. Maybe this is my problem? I thought fuel systems on boats should be to "pull' fuel from the tank for those silly fire risks that never occur. Do I have this wrong also?

[redlowrey]

No mate when the key is turned on the ecm pcm will supply battery voltage to the fuel pump relay for 1 second and if it has not received a crankshaft reference pulse it will turn off battery voltage, ford is the opposite it supplies the fuel pump relay ground. Your Suzuki will do the same thing, when you turn the key on it will supply a ground for two seconds if it do's not receive a crank signal it will remove the ground and the pump will switch off. Remember this Suzuki uses duty cycle on the fuel pump ground, in the early days with vapour lock problems people were wiring a full ground on the fuel pump so that it would put out 100% output when ever the key was turned on, this is why I often say if you think you have a fuel problem connect up a pressure gauge and monitor the fuel pressure.

[Lostsoul58]

I realize I am being a smartass. Just frustrated. Apologies all. My particular issue occurs from mid-May until mid-October. That's when temps here are 85 and higher. Never does occur in winter or early spring. It's temp related. I've been chasing what I perceived as a fuel problem. Could it be anything else such as an ignition module and/or sensor?

[briscoe]

It's the formula of gasoline when I have issues

I have run into some of those issues here in the great state of TX, when the spring temps are turning summer.
You see refineries are required to make winter blended gasoline and summer blends. Winter blends will have more light components such as butanes and pentanes. The higher RVP gasolines flash off more in summer. This contributes to overwhelming my gas cooling to VST.
Hence summer days give me some of the same issues as you. I have learned to solve it by filling up with regular (ethanol), summer blends. We start using lower RVP gas in April and May, down south. Further north it's May or June. Fill up with summer gasoline and it may solve your issues as I discovered, it solved mine.
Lighter gasoline was my Suzuki's worst enemy, in the summertime. Hot days required bulb pumping until I used up the winter blend. This is RVP not octane. Lighter components = lower vapor pressure.
Just a suggestion, which solved my issues.

[Lostsoul58]

I have run into some of those issues here in the great state of TX, when the spring temps are turning summer.
You see refineries are required to make winter blended gasoline and summer blends. Winter blends will have more light components such as butanes and pentanes. The higher RVP gasolines flash off more in summer. This contributes to overwhelming my gas cooling to VST.
Hence summer days give me some of the same issues as you. I have learned to solve it by filling up with regular (ethanol), summer blends. We start using lower RVP gas in April and May, down south. Further north it's May or June. Fill up with summer gasoline and it may solve your issues as I discovered, it solved mine.
Lighter gasoline was my Suzuki's worst enemy, in the summertime. Hot days required bulb pumping until I used up the winter blend. This is RVP not octane. Lighter components = lower vapor pressure.
Just a suggestion, which solved my issues.

That's treat if you have an option. I don't. The marina where I refuel sales Valvtech fuel. I think it's worthless. I refueled last Friday and the loss of power issues all day Saturday. There is a vent port on the VST. I am going to try and find a threaded nipple that will fit that vent and route a vent hose up towards the cowl vent to allow these vapors to easily escape. That won't stop the hot weather from boiling the VST fuel but it will relieve the vapor so that fresh fuel can quickly enter. Has there ever been any Suzuki issued Technical Service Bulletines issued for this problem???

[Lostsoul58]

Let me ask this another way...
Was there ever a Technical Service Bulletine issued by Suzuki Marine Division for the Suzuki vapor lock issue?
Again I can only speak from my past 35 years experience in the Public Safety/Law Enforcement Fleet Management career but.... If there were problems with particular vehicles the manufactures would issue TSBs recommending a solution/fix, even for non warranty and/or recall corrective measures. Where has Suzuki been while folks (customers) are posting and struggling to find a solution? I am not hearing that anyone here is asking for a free ride. Just guidance for a real and final solution.

[Moonlighter]

I am probably going to the Brisbane International Boat Show this weekend. A couple of Suzuki master mechanics I know will likley be there. I will ask them re both the TSB issue, and the solution they recommend for you. They've been around Suzukis since way back when..... So i expect they will know. I might add that dealers hold TSB's pretty closely to their chest, not things that are released to the public very easily.

This is quite an uncommon problem to hear of these days. It was around a bit up to about 2010 but rarely heard of since then. Even on this forum, reports are few and far between.

But anyway, will see what I can find out for you.

[Lostsoul58]

I am probably going to the Brisbane International Boat Show this weekend. A couple of Suzuki master mechanics I know will likley be there. I will ask them re both the TSB issue, and the solution they recommend for you. They've been around Suzukis since way back when..... So i expect they will know. I might add that dealers hold TSB's pretty closely to their chest, not things that are released to the public very easily.

This is quite an uncommon problem to hear of these days. It was around a bit up to about 2010 but rarely heard of since then. Even on this forum, reports are few and far between.

But anyway, will see what I can find out for you.

That would be most appreciated!
For what it's worth my motor is a 2007 DF200 with less than 225 hours of use. Thanks for your help.

[Striperk9]

I am probably going to the Brisbane International Boat Show this weekend. A couple of Suzuki master mechanics I know will likley be there. I will ask them re both the TSB issue, and the solution they recommend for you. They've been around Suzukis since way back when..... So i expect they will know. I might add that dealers hold TSB's pretty closely to their chest, not things that are released to the public very easily.

This is quite an uncommon problem to hear of these days. It was around a bit up to about 2010 but rarely heard of since then. Even on this forum, reports are few and far between.

But anyway, will see what I can find out for you.

I would appreciate this as well. If it takes a supplemental pump, I am fine with this. Kind of curious what the change was in 2010. My motor is older as well. 2005 with only 320 hours.

I had a friend who told me he would be more afraid of an old motor with low hours than a new motor with high hours. Starting to understand what he meant.

But I think there is a fix for myself and Lost Souls.

Thanks to all for the advice!

[Moonlighter]

I will let you know what I find out.

As to what happened around 2010 or perhaps a little earlier, as someone posted earlier, the fuel rail was redesigned, and possibly other changes as well to low pressure fuel pump, that eliminated the problem.

[Moonlighter]

Well, as Tonto said to the Lone Ranger, " I have the information, kimosabe"

Spoke to one of my Suzuki gurus at the show. He has been in the Suzuki game simce before the 4 strokes were introduced. He knew straight away about the issue, immediately said it wasn't a vapour lock issue, and remarked that he had only ever seen barely a small handful of cases years ago, mostly from motors pre-2008.

I will try as best I can to describe the cause as he explained it to me.

He said it is more boat related than it is an engine issue.

The issue is to do with the duty cycle of the low pressure fuel pump when the engine is at idle or low revs, up to about 3000rpm. The ecu cycles the pump on and off in a preset sequence at these revs. Once the engine hits 3000revs (or thereabouts) the ecu then makes the pump run constantly.

The low pressure pump provides fuel to the VSR chamber.

On a very small number of boats, due to the fuel tank placement, combined with things including the length between tank and motor, how the fuel lines are run, filters, fuel restrictions, and primer bulb placement, at low revs, the duty cycle does not keep up with the fuel being used and/or some fuel runs back towards the tank.

This causes the fuel level in the VSR to drop below a sustainable level and when the throttle is opened, there is insufficient fuel to feed the hp fuel pump and the engine starves. He recalled one boat where the owner lived on a canal so had a 10 minute trip at idle speed from his pontoon to the canal entrance where he could then open up the throttle - a perfect scenario for this issue to occur.

So it isn't actually a vapour lock issue at all!!!

The fundamental cause is insufficient fuel getting to the low pressure fuel pump, the pump not being able to suck enough fuel and/or fuel draining back thru the lines.

He said Suzuki, in later models, changed the low pressure fuel pump duty cycle settings to provide a longer running sequence at lower revs and that is why this issue doesn't occur with later engines. Unfortunately the LPP duty cycle is hard coded in the ecu and cant be changed in these early motors.

So we then had a chat about how to solve the issue.

- I mentioned the fuel rail change someone had suggested earlier as being the solution, but he said that was nothing to do with this issue.

- I mentioned the use of the small inline electric fuel pump - he said - yes, you can do that, but in his view it is a very last resort solution because it is treating the symptoms, not the cause.

So we had a further discussion about what to do to address the root cause, being insufficient fuel getting to the low pressure fuel pump. In other words, the boat's fuel system.

He said he would start at the tank and work forwards to the motor and to do everything possible to improve fuel flow to the engine, as follows:

1. remove the anti-syphon valve. It takes some initial "sucking" to crack open these valves and that can add to the load on th LP pump.
2. Replace all fuel lines between the tank and engine, and using one size larger hose wouldn't hurt. Make sure there are no kinks or restrictions in the line, lay it as straight as possible, and avoid it going downhill and uphill again on its path to the fuel filter.
3. Be certain to place the primer bulb between the fuel filter and the engine, NOT between the tank and the filter.
4. Replace the fuel filter element with a new high quality one and replace it regularly.
5. Use a new top quality primer bulb - he likes the new Suzuki ones, but also said the new Yamaha ones are very good too. These have good internal valves and can prevent fuel flowing back away from the engine.
6. Make 100% certain that the primer bulb is placed so it is vertical, with the arrow pointing upwards.
7. At every point in the system where the fuel line is connected to something (eg the filter, primer bulb etc) use an appropriate sealant on the join to minimise any chance of air leaks. And obviously make sure all hose clamps are fitted tight.
8. Replace the tank breather lines or at the least, make certain they are clear and unobstructed so the tank can breathe really freely. If in any doubt, add extra breathers. Check for mud wasps!

And last resort if you've done all that and it still happens, the small electric fuel pump put line as discussed previously.

Hope that advice from the expert helps.

[Lostsoul58]

Thanks for taking the time to research this problem and respond in such great detail.

Since the pump cycle is "programmed" in the system and everything recommended has been done (and it has) then the additional pump is indeed the last resort.

I'll always wonder though why it's only during hot temperatures and after there is a "hot soak" period....

Thanks again Sir.

[redlowrey]

Why don't you take a temp gun out with you the next time you get a hot day, and when it plays up stop and take the cowl off and shoot some temps on the vst cyl heads exhaust and so on. Or if you don't want to do that take the boat to a Suzuki dealer and get all the data pids read and check the cyl temp, and exhaust temp, it will give you the temp and voltage for each one and a heap of other information that might shed some light. Has your engine got a water cooled fuel rail and a water cooled vst.

[Striperk9]

Thanks, Moonlighter!

Moonlighter, I really appreciate you taking this to the experts. I will definitely try and make sure the fuel flow is as free as possible. Someone else recommended taking off the anti-siphon valves as well.

Still not understanding why mine is resetting if I shut down (and then runs fine), but it could be that the fuel pump gives that short boost at the "on" position and that is the extra push it needs. Definitely more pronounced in hot weather conditions. But I could see where cooler fuel lines and tighter fittings could account for the difference in pump efficiency.

Thanks again!

Lost Souls, glad to see you are a fellow TarHeel as well. (from the 'water pump change' thread)

[Moonlighter]

Yes, that us exactly what happens - if you turn the key off and then on again, the low pressure pump is restarted and pumps for a set time to bring fuel level up.

In fact my Suzuki expert said that simply by turning the key on and off a couple of times this would clear the problem. Its not an ideal solution but it is further proof the problem isnt vapour lock.