Df140 2008 rpm

[KasperS]

Hello Suzuki people!
I have a used DF140 i recently bought. The problem with the engine is that each time it has been on for 5-10 minutes it starts to sob and fall in RPM. Before it starts to sob it will run 5500+ rpm and ends around 3200 rpm and stays there untill you turn it off and it will then run 5500+ rpm again, but only for a very short time. I have searched a lot on this fantastic forum, but I've not had any luck so far.
Things I've tried so far:
Bypassed the squeeze pump.
Ran the motor with injection cleaner.
Cleaned the air filter.
Changed the fuel filter. (not the high power)
Changed the waterpump
Changed the thermostat.

The engine does not enter the emergency program.

Right now im out of ideas what's causing the problem??

Regards Kasper

[redlowrey]

I sob when I don't get my own way. Jokes aside it sounds like fuel, if no lights are coming on when the rpm drops, it could be the high pressure fuel filter or it may be the gauze filter blocked in the vst. if it came into my workshop with those symptoms I would be fitting a fuel pressure and flow gauge on it first up, and then checking the neutral switch on the motor to make sure it is not stuck closed because that will keep the rpm at 3000. It is easy to check that, just try and start the engine when it is in gear, if it starts you know the switch is crook.

[bigdude2468]

I don't see a fuel issue. If a filter is blocked / clogged it would not run properly from the start. It sounds like the engine is going into the limp mode and restricting RPM's. The alarm may not be working alerting you to the issue. Check the tattle tail stream from the engine and you may want to get a temp gauge to be sure the engine is not overheating and you are not aware of it.

[redlowrey]

Any limp home problem will bring the the lights up on the dash, except the neutral switch which l stated in my fist post. If it was a carbureted engine it would defenatly splutter bad, low fuel pressure on a multi point injected engine will drop in rpm and not miss like a carbi engine until the rail is very low. what you are saying makes sense, but he says no limp home stategey, if it was a temp problem the check engine or temp light should be on. l can only go on the information provided.

[catacom225]

DF 140 rpm

Kaspers,When in Limp mode your engine in in protection mode and the RPM will alternate between 3000 rpm and 1000 rpm every second or so, If your engine will maintain 3200 rpm it would sound like its fuel related

[bigdude2468]

Guys, he says it runs fine for a few minutes then the RPM drops. A bad filter(s) bad fuel or similar would happen from the get go.

[Moonlighter]

I had a bad load of fuel a couple of years ago. Found out when i threw the boat up onto the plane and accelerated up to near full speed - then she starved and almost died. It happened a couple of times on that trip. Took it easy to get home.

I replaced the Racor filter element later that day and found it was partially clogged, bits of rubbish floating in the clear bowl too.

Enough fuel was getting thru at idle and mid range, but up the revs over 5000 for any length of time and it would starve.

A new filter element solved the problem. I did another element change a few tanks later just to make sure that i had got the majority of the dirty stuff filtered out.

So a partially clogged filter can be a cause of those kinds of problems. These 4 strokes use so little fuel at idle and low revs that they can cope with restricted fuel flow much better than you would expect.

Ive also seen fuel lines where the inside lining had started to break down and again, at higher revs, this is when the restriction in fuel flow will become apparent.

So to the OP - if tye fuel lines are old, consider replacing them, or at least remove lines and inspect inside to see if they look good. You cant tell from the outside if they are breaking down inside. Although, if they are really bad,when you squeeze the lines it might feel crunchy......

Also look for any kinks in the fuel line in the engine itself, and from the tank all the way through to the engine, and in the breather lines.

[KasperS]

Thanks for all the suggestions, I'll definitely try some of them in the upcomming days!
Kasper