DF140 Rough running/Not starting. Help Please!

[simon-666]

Did 100 miles on the boat last week and it threw a fault code and starting running rough just as i was putting it back on the trailer.
The motor is a 2007 DF140 with 180 hours on it.

Dash shows code 3-2. (MAP pressure not as expected.)

Found the IAC valve was a dead short, borrowed a known good one from a friend. - Wont start.

I can sometimes get it to start by removing the IAC and controlling the air using my finger! but when its running it doesn't sound right. Almost like a missfire.
If the engine stops it wont re-start.

Compression tested - all 4 cylinders at 170.

Low pressure fuel pump tested. - ok

High pressure pump removed and stripped, no sign of any dirt anyway. Fuel pressure tested at 37 psi as per spec.

All fuel filters changed.

I have a SDS lead and software.
all readings check out. Nothing out of the ordinary. The MAP sensor is reading fine, i think the failed IAC caused the alarm code.

If i manually activate the IAC valve it just buzzes, i dont see the vale open. Is this normal? I'm wondering it the ECU may have been damaged by my old IAC which went dead short?

All 4 plugs are very black and carbonized, and wet with fuel.

Any ideas clever people?
I have a sponsored boat run next week in aid of Cancer Care Charity, and things don't look good.
Thank you.

[redlowrey]

What made you come to the conclusion that there was a short in the iac, if there was a short to earth it would have blown the thirty amp fuse. The first thing you want to do is replace the spark plugs, if the engine started missing manifold vacuum will drop and the higher signal line voltage could bring on the map sensor code. If you checked the iac connected up when the engine was running, it will buzz because the ecu duty cycles the earth. What was the coil resistance of the iac, it should be between 8 and twelve ohms. how did you test the iac.

[simon-666]

The old IAC coil was a dead short.
Tested with a meter. 100% confirmed.
The new one reads about 9.7 ohms.

I dont think a 30 amp fuse would have blown. More likely the MOSFET output driver on the ECU would have fried.

I have had a scope connected to the IAC output from the ECU and confirmed the ECU is chucking out a PWM signal, but the way the valve just buzzes seems there is insufficient current to open the valve.
The attached pic shows the scope when at idle.

I agree with you about the plugs. i have bought a new set to try today.
I agree with the MAP sensor during a misfire situation. I guess i need to look at the coils and injectors next?

I can hear each injector firing when activated using SDS.

If someone has SDS and wouldn't mind telling me if they see the IAC valve physically open when manually activating it i would appreciate it.

[redlowrey]

If you connect battery voltage up to the iac and connected a ground on and off, you will see the plunger retract in an out. I have never connected an amp meter to one, but I would not think it would draw one amp while it is being duty cycled. When you get the motor running hook up a duty cycle meter to it and watch when cranking it should read between 80 and 90% and drop as the motor warms up. Make sure you check that the spark is good. I have found when trying to check any idle speed control motor that has a constant frequency sent to it, won't produce a nice square wave on the scope to read. I switch to special patterns on a 25 volt scale and five milli second division and the pattern looks more like a shark fin, and as the loads change the width of the pattern changes and is easy to read. The only thing I can think of the magnetic field that is produced by the iac coil changes the shape of the pattern.

[simon-666]

Hi
The Square wave you see on my scope was measured without the IAC connected. I used a 10 ohm resister to simulate the load.

I can use SDS software to manually activate the IAC but it just buzzes, i dont see the valve physically open. Is this correct?

The engine wont start with the IAC in place as i guess its not opening on cranking.
I can get the engine to run with the IAC removed and the hole partly covered using tape, but it runs very rough.
If i rev the engine (covering the IAC hole with my finger. it coughs, splutters and pops. missfires like a cow.
(this is with the new plugs fitted)

I have read on other forums tales of peoples IAC going short and taking out the ECU.
As there seems too little output from the ECU to open my IAC, i am wondering if its affecting the HT coils and injector outputs too causing the rough running?

Compression test comes back all around 170, but a mechanic reckons the head gasket has gone??? Could this be correct with good compression?

I have a friend sending down another ECU from a DF140 which i will try. If this doesnt fix it, i guess its head off time.

Here is a video of it running: https://www.youtube.com/watch?v=sRMlA5h3muc

[Hawaiian GP]

Simon, did you ever fix the df140? I have the same symptoms and can't figure it out.

[Harper]

Simon, did you ever fix the df140? I have the same symptoms and can't figure it out.

Simon hasn't been back on the forum since he had the problem. Been almost 2 years now.

But if you'll tell us about your problem in more detail and what you've done in the way of diagnoses so far, I'm sure you'll find plenty of help.

[simon-666]

Sorry I'm still here now and then!

Yes I've sorted the motor and it's running perfect again.

I connected my scope to the flywheel crank sensor output and the cam shaft position sensor. I noticed the sensor pattern was out of sync compared with the pattern in the repair manual.
So I stripped off the rocker cover.
Inside I found the timing chain tensioner had completely fallen off. The chain was very lose .
The exhaust valve cam (left hand one) had jumped several teeth!

You can see this here:
https://youtu.be/xOy9KvLrWJE

Unfortunately the fix involved removing the power head. While it was off I also replaced the oil pressure relief valve with the modified version which stopped that stupid noise when it's at idle on pre 2010 motors.

I found the chain tensioner bolt in the sump pan. It got replaced and the new one put back in with thread lock!

[Hawaiian GP]

Mike and Simon thanks for responding. My DF140 misfires on #2 cylinder and the plugs are black. #2 plug is black and wet with fuel. I changed both fuel pumps, fuel lines, both temp sensors, ,IAC, thermostat, map sensor, oil pressure switch, wiring harness, fuel filters, oil cooler, and the white wire that goes to the battery. Compression is at 170 on all cylinders. So I've come to the conclusion that either the ECU was bad or the timing was off. What Simon said about his timing chain makes sense for my situation also, so I'll investigate further into it.
BTW Simon did you remove your flywheel to remove the power head? Only reason I ask is the manual says to do so but I see no reason for me to do that.

[simon-666]

No need to remove the flywheel.
I didn't even remove the wiring loom and some hoses.
There was enough slack in the loom to allow the power head to be lifted to work on the chain.

Mine was still running also but making a lot of black soot around the exhaust on the prop.

Just take off you cam cover to check the chain.

[Moonlighter]

Hawaii- Did you connect it up to the Suzuki SDS system to see what it was showing? Or to run diagnostic tests - eg injectors?? One bad plug, lead or injector could be discovered that way....

Every Suzuki dealer has these systems and should know how to use them to diagnose and test the motor. May save a lot of time and effort and avoid work and parts that are not needed.... better than just replacing things and hoping.

I imagine youve also checked for the exhaust corrosion issue (assume this is a 2008 oe earlier motor)on the engine holder near the flushing port on the port side?

[redlowrey]

Mike and Simon thanks for responding. My DF140 misfires on #2 cylinder and the plugs are black. #2 plug is black and wet with fuel. I changed both fuel pumps, fuel lines, both temp sensors, ,IAC, thermostat, map sensor, oil pressure switch, wiring harness, fuel filters, oil cooler, and the white wire that goes to the battery. Compression is at 170 on all cylinders. So I've come to the conclusion that either the ECU was bad or the timing was off. What Simon said about his timing chain makes sense for my situation also, so I'll investigate further into it.
BTW Simon did you remove your flywheel to remove the power head? Only reason I ask is the manual says to do so but I see no reason for me to do that.

''''''Óne would think that the chain rattle at start up would be telling you something, and in simon 666 problem the tensioner actually fell off, how would you not hear any noise long before it got to that stage.

[Hawaiian GP]

Just to give a little more insight ; My engine is a 2011 with 120hrs on it. I haven't run the SDS on it yet. The harness is new so the leads/ plugs are good. I have a second set of injectors and swapping them makes no difference. I did hear a slight knocking a few months ago but not now. My exhaust water was mixed with a lot of soot but not now. Spark plugs are new. I imagine if my timing chain jumped a few teeth I would be having these symptoms. I'll see if I can get my computer to connect with the ECU. Rich

[simon-666]

''''''Óne would think that the chain rattle at start up would be telling you something, and in simon 666 problem the tensioner actually fell off, how would you not hear any noise long before it got to that stage.

No unusual rattle. There is a video of it running in my first post. Hear any rattles?

HawaiianGP: I make SDS cables for my UK boating group. Drop me a private message and ill send you the instructions.
I had it on SDS but it didnt help. Yes you can fire all the injectors and view sensor data etc.
I was lucky enough to have a friend with a DF140 in bits he uses as a donor engine for his fleet of training craft. So i managed to borrow and steal parts from him. I tried swapping ECU's but this made no difference.

The only difference is all my plugs were getting wet and sooty after a short run at idle. where yours is only Cyl no.2?

I would whip the rocker cover off before you do any more. If i had known how close i came to smashing the cylinders into the exhaust valve, i dont think i would have run it quite so much!

I did put a bore cam through the plug holes to check the cylinder/valves and all was good

Yes i did change my exhaust blanking plug for a G0ldPlug while the cover was off. Looks like a got to it just in time too.

[redlowrey]

Mike and Simon thanks for responding. My DF140 misfires on #2 cylinder and the plugs are black. #2 plug is black and wet with fuel. I changed both fuel pumps, fuel lines, both temp sensors, ,IAC, thermostat, map sensor, oil pressure switch, wiring harness, fuel filters, oil cooler, and the white wire that goes to the battery. Compression is at 170 on all cylinders. So I've come to the conclusion that either the ECU was bad or the timing was off. What Simon said about his timing chain makes sense for my situation also, so I'll investigate further into it.
BTW Simon did you remove your flywheel to remove the power head? Only reason I ask is the manual says to do so but I see no reason for me to do that.

''''''Nearly all the things you changed would have nothing to do with your problem, only the map sensor and the temp sensor would have a direct bearing on the problem. You don't mention anything about checking for spark, or swapping coils, fuel pressure, checking and making sure you had manifold vacuum at the map sensor hole, checking the signal voltage at the ecu for the map sensor, temp sensor, air temp sensor, and the exhaust temp. Any four cylinder engine running a map sensor, the moment one cylinder drops out the map signal voltage will go high and make the engine run rich sooting up the plugs. It could very well be a chain problem, but for that to happen the engine would have played up straight away while you were cruising, and straight away you would have had the problem, you make no mention of that.