DF50 Runs great won't start immediately once off

[Perfdavid]

I have a 2000 DF 50.
I joined this forum hoping to get an answer for my problem that occurred this past weekend.

It starts wonderfully and runs great. However, once I turn it off it will not restart immediately. I have to wait two or three minutes to turn it over again before it will start. It will just crank and crank and do nothing unless those few minutes have passed by.
The gas bulb on the line is fine and works well. The fuel is non-ethanol and I have only run non-ethanol. The impeller is obviously working because a nice steady stream of water is coming out of the motor.

I have read on other sites that this can be a problem with this motor? Is it vapor lock? Is it a possible heat issue?
Has anyone else had a similar issue like this and know what the remedy is?. Any help would be appreciated. My concern is being out there and it will never start.
Thank you in advance for any comments

[Perfdavid]

I have come to determine after much reading it must be vapor lock. 4 stroke 2001. I have rebuilt older car engines but haven't messed with outboards. Should I try to install the low pressure fuel pump myself or have a shop do it? Difficulty level?

[Moonlighter]

Have you done everything possible to reduce restriction (and improve fuel flow) in the fuel system between the tank and engine?

Eg

- Removed anti-syphon valve from tank
- Ensured that the filter on the fuel tank pickup tube is totally clear
- replaced fuel lines between tank and engine and made sure they are correct size
- replaced water separating fuel filter (Racor style) on the fuel lines
- made sure the primer bulb is pointing upwards
- breather line on fuel tank is clear of all obstructions and flows air well
- all joins in fuel lines are airtight
- no kinks or sharp bends in fuel lines anywhere.

There is quite a bit of debate about this issue. I recently had a long conversation with a master certified Suzuki tech who has been in the game of servicing these 4 stroke Suzuki motors since they first came out.

His view is that it is not a vapour lock issue, but is a fuel supply issue where fuel drains back out of the engine when it is stopped.

In later engines, he says Suzuki increased the duty cycle for the electonic fuel pump on startup and this solved the issue.

But he says that improving fuel flow to the engine is the core of the solution, and his view is that adding the extra electronic fuel pump in the line is largely treating the symptoms of restrictions in the fuel system, not the cause.

Hence the suggestions above.

[Perfdavid]

Have you done everything possible to reduce restriction (and improve fuel flow) in the fuel system between the tank and engine?

Eg

- Removed anti-syphon valve from tank
- Ensured that the filter on the fuel tank pickup tube is totally clear
- replaced fuel lines between tank and engine and made sure they are correct size
- replaced water separating fuel filter (Racor style) on the fuel lines
- made sure the primer bulb is pointing upwards
- breather line on fuel tank is clear of all obstructions and flows air well
- all joins in fuel lines are airtight
- no kinks or sharp bends in fuel lines anywhere.

There is quite a bit of debate about this issue. I recently had a long conversation with a master certified Suzuki tech who has been in the game of servicing these 4 stroke Suzuki motors since they first came out.

His view is that it is not a vapour lock issue, but is a fuel supply issue where fuel drains back out of the engine when it is stopped.

In later engines, he says Suzuki increased the duty cycle for the electonic fuel pump on startup and this solved the issue.

But he says that improving fuel flow to the engine is the core of the solution, and his view is that adding the extra electronic fuel pump in the line is largely treating the symptoms of restrictions in the fuel system, not the cause.

Hence the suggestions above.

Mine is a simple 6.5 gallon plastic tank with line running to the outboard. This is the first time this issue has happened. That being said, I never really have cut off the engine and then restarted it right away after it was hot. This engine is on a sailboat and I usually sail for many hours after turning it off. So, it has plenty of time to cool down.
I have a new fuel line which I am thinking about shortening before I attach it. The bulb really just lays flat. I also noticed I only need to wait 2-3 mins before it will restart. It was an exceptionally hot day this past Sunday which makes me think it is vapor lock. I have not run it WOT because I only need 3000 rpm to get 6knts when under poser on my sailboat.
I am wondering if I need to even really worry about this issue at all

[Moonlighter]

Ok, it really helps when we know the full story.

It's a pretty big call to make that the problem is vapour lock after just the one incident!

In any case I would suggest:

- Make sure the breather vent on your tank is fully open and working properly. (You wouldnt be the first one of us to forget that!)

- Also, yes, would be - good idea to replace those lines and shorten them

- do everything possible to position the primer bulb so the fuel flow is up-hill - in other words, the end closeset to the engine is higher. The primer has a simple one-way valve inside and it really only works properly when positioned that way, both to pump fuel and to prevent drain-back. In your situation as you described it, the fuel has plenty of time to drain back down which would contribute to difficult starting.

- if the problem happens again, pump the bulb up hard and then try starting again. Should then start straight away.

- I am only guessing where the tank location is, height wise, to your engine. Try to position it so that the tank is at a similar height to the engine, or at least not on a much lower level - again the rationale is that the least height that the fuel pump has to lift fuel from the tank to the engine, the better.

- also, even though you run a portable tank, I highly recommend you install a Racor style fuel filter between the tank and the engine. I have a small estuary boat running a DF40 tiller and the first thing we did was install one of them.

The fact is that EFI systems absolutely hate dirty fuel or fuel contaminated by water. And one of those filters is your primary source of protection from such contaminants. They should be mandatory, IMO.

Again, do your best to place it in a position at the same level as the engine, not lower. Far, far cheaper and easier to clean out and replace one of those filters than it is to replace all the engine filters and clean out VST's, fuel rails and injectors!

When was the last time the water pump was serviced? Again a strong pee stream is not the perfect indicator of a water pump that is fully up to the job, there is another thread currently where someone else found that out!

A final thought - how fresh was your fuel when this issue happened?

[Perfdavid]

Ok, it really helps when we know the full story.

It's a pretty big call to make that the problem is vapour lock after just the one incident!

In any case I would suggest:

- Make sure the breather vent on your tank is fully open and working properly. (You wouldnt be the first one of us to forget that!)

- Also, yes, would be - good idea to replace those lines and shorten them

- do everything possible to position the primer bulb so the fuel flow is up-hill - in other words, the end closeset to the engine is higher. The primer has a simple one-way valve inside and it really only works properly when positioned that way, both to pump fuel and to prevent drain-back. In your situation as you described it, the fuel has plenty of time to drain back down which would contribute to difficult starting.

- if the problem happens again, pump the bulb up hard and then try starting again. Should then start straight away.

- I am only guessing where the tank location is, height wise, to your engine. Try to position it so that the tank is at a similar height to the engine, or at least not on a much lower level - again the rationale is that the least height that the fuel pump has to lift fuel from the tank to the engine, the better.

- also, even though you run a portable tank, I highly recommend you install a Racor style fuel filter between the tank and the engine. I have a small estuary boat running a DF40 tiller and the first thing we did was install one of them.

The fact is that EFI systems absolutely hate dirty fuel or fuel contaminated by water. And one of those filters is your primary source of protection from such contaminants. They should be mandatory, IMO.

Again, do your best to place it in a position at the same level as the engine, not lower. Far, far cheaper and easier to clean out and replace one of those filters than it is to replace all the engine filters and clean out VST's, fuel rails and injectors!

When was the last time the water pump was serviced? Again a strong pee stream is not the perfect indicator of a water pump that is fully up to the job, there is another thread currently where someone else found that out!

A final thought - how fresh was your fuel when this issue happened?

Technically, it wasn't one incident. It happened 7-8 times. It was just this one day, mainly because it is the first time I ran the engine, cut it off, and tried to restart the boat right away. I have only had the boat for 3 months now and I usually raise my sails once out of the bayou and into Lake Pontchartrain. So, I have not noticed it before because of how I use it.
The lower unit was completely overhauled right before I purchased the boat by a marine mechanic.
Fuel is brand new and non-ethanol.
Fuel tank is close to the same height as the engine and the fuel line is about 4ft long.
I'll definitely add that filter, great idea.
The temp on the water that day was around 92.

[fish_eater]

seafoam try it.

I have the same engine. Suzuki has neutral switch at the throttle.
It could be bad. You can short it and test if engine starts.

[Harper]

seafoam try it.

I have the same engine. Suzuki has neutral switch at the throttle.
It could be bad. You can short it and test if engine starts.

Wrong. If it were a problem with the neutral switch, it wouldn't even crank.