WOT Issue (No longer a maybe!)

mvn

Background:  2019 Rinker MTX20 with a Volvo V6-280-M/SX drive package.  I purchased it at the beginning of summer from a dealer that had it stored for over 2 ½ years with a ½ tank of fuel in it.  It had 5 hours on it when I got it.  It now has 25 hours.

 

The Story:  First weekend with it, all seemed good.  Acceleration was incredible, even with 6 people on board.  I had to get used to the very sensitive throttle.  I had to increase the throttle friction setting a bit which helped.  The next weekend is when the trouble started.  I did a single WOT throttle run to see max speed.  The tach appeared to almost hit 7,000 rpm.  I backed off immediately.  No rev limiter, no alarms…..strange.  A few hours later, I started to get a recurring alarm as previously posted.  Getting a Rinda scan tool, the code was SPM 4237 FMI 0 which translates to long term fuel trim high, Bank 1 indicating a lean operating condition.  Subsequent investigation found a very loose fuel filter so I suspected fuel aeration as the low pressure pump was also gurgling.  Changing out the fuel filter and tightening it up, I did not get the code again.  I also reset the fuel trim table so the ECM could relearn.  WOT indicated 5800 rpm on the boat’s tach but the speed seemed low (43 mph on GPS).  Prop was a stock 14x19 4-blade aluminum.  I didn’t think too much of it but it stayed in the back of my mind.

 

Fast Forward to Yesterday:  I got a 14x20 4-blade stainless to try this past weekend.  Handling improved dramatically but the top speed did not improve.  WOT indicated 5800 rpm on the boat’s tach (same as stock prop).  Loading up with 6 teens/adults, we headed out for a day on the water.  All seemed to be OK but I found the boat to be sluggish getting on plane while towing.  This was not the case on that first weekend while running stock prop.  It was able to pop up a skier in no time.  Later that day, I went out with my scan tool and did a few WOT runs.  Low and behold, the Rinda scan tool showed ~4900 rpm while the boat’s tach showed 5800 rpm.  The scan tool also showed max engine load at 86% to 88% regardless of prop.  I did not get a chance to verify the switch setting on the tach…next weekend.  I did verify full stop to stop operation of the throttle position sensor so cables are OK.  Oil pressure, coolant temps and manifold temps are all good according to the ECM and gauges.

 

So my question is this…..Assuming the tach is wrong (which would explain the 7,000 WOT reading last month) and its really 4900 rpm, what do I do?  I did read the thread on another forum regarding low WOT.  I suspect fuel issues.  I have been filling up with ethanol-free premium gas to flush the system but could there be a partial blockage somewhere due to the 3 year old fuel?  Any ideas where?  I was thinking of setting up a small tank with regular gas and Sea Foam and feeding the low pressure pump to see if it’s a tank issue or an engine issue.  I’ll also change the filter again and look at the contents.  I may also pull the main tank fuel pickup and inspect.  Is there a socket/screen on the intake?

Mark

YYZRC

I put STP fuel system cleaner in my boat and problems started. I believe that it loosened crud in the fuel system which then clogged the injector(s). Both my starboard engine and genny have been acting up since. I would avoid that stuff. 

captkevin

Some tachs have switches on the back to adjust for different engines. Could be set in wrong position. Or tach could be bad. 4900 rpm would seem to be about what you would expect.

Might have to experiment around until you find the right prop for your use. You went up in pitch so it makes sense that bottom end would suffer.

mvn

WOT spec is 5400 to 5800 on this engine.  Prop change has nothing to do with the gross difference. Did the same thing with the stock prop. I haven't checked the switch setting yet. 

YYZRC

Did you check plugs, wires, cap, rotor? Maybe a loose spark plug wire. 

earl1z19

The Faria tachs are known for not reading correctly, tap on the glass and it may go back to reading correctly.
The sluggishness you are experiencing is probably the result of going up 1 inch in pitch on the prop. Your are running a v6, while it may have 280hp it doesn't have huge amounts of torque. You had the boat loaded down with 6 people and gear and that's a bunch to ask from a v6. I would go back to the original 19P prop and call it a day. Rinker put a 19p prop on that boat for a reason.

mvn

Same performance and observations with stock prop. Something changed huge just after I got it and started using it. The very first day I got it, it was like a sports car.  A few trips later, the sluggishness began. 

captkevin

Did you change fuel filters?

mvn

Yes, changed fuel filter.  I'm assembling a bunch of diagnostic tools right now (fuel pressure gauge, etc) and new filters.  I'll be checking pressures first across the entire operating range.  If there are any anomalies, I'll be checking the high-pressure pump screen and/or pressure regulator screen for contamination.  After that, I'll run on a separate small tank.  My goal is to rule out fuel starvation.

Mark

aero3113

Have you changed plugs, wires, cap and rotor?

mvn

Have not changed anything ignition-wise.  It's only got 20 hours on it.

YYZRC

Cap/rotor goes to s**t in two seasons for me. 

mvn

Wow....really?  I'll add it to the list.  Thanks

aero3113

Do that first before you do anything else.

mvn

Coil over plug system, no cap/rotor to check.

captkevin

As new as it is you should have no problems. Maybe talk with dealer you bought if from to see if there are any known problems. Do you keep it on the trailer or in the water?

mvn

I keep it in the water on weekends but on a trailer during the week. I'll have more info after the weekend. 

aero3113

Maybe a coil pack went and you’re not running on all cylinders.

mvn

I might be able to do a cylinder cutout test with the Rinda TechMate. 

raybo3

@mvn what model Rinda do you have and how much was it?

mvn

I got the Techmate Pro from Michigan Motorz. I ordered the one that came with a bunch of inboard/sterndrive adapters.  I think it was around $600.  The Diacom package is nice if you can deal with using a laptop. 

captkevin

Is there any chance the problem stems from resetting the fuel table on the ecm? Other than that you really have not made any changes from when you got the boat.

mvn

Good thought but no, change happened before resetting fuel table.  No changes were made prior to rpm/power drop. 

Mark 

mvn

Learning about this engine.......

It's a Gen V direct injection setup.  I've learned that the high pressure side should be 2250 psi at WOT.  Thankfully, the scan will show this data.

Low pressure side is running 18 psi.  Not sure what the correct spec is. 

Still getting intermittent SPN 4237 FMI 0 Long Term Fuel Trim High (lean) Bank 1.

Faria tach is way off and neither Setting 2 (too high) or Setting 3 (too low) work perfectly.  Weird...... In any case, WOT way too low. I'm using scan tool rpm reading. 

I'm suspecting a dirty/plugged injector(s) due to the 3 year old gas.  As mentioned earlier, I'll try a portable tank tomorrow with injector cleaner suitable for DI systems and a new filter. 

Mark 

mvn

#3 cylinder is dead.  Injector cutout test confirms.  Also, pulling off the spark plug wire does not affect anything either.....does not run worse.  So it's either spark or injector.

Royal Purple injector cleaner (3 gallons of mix). 

Mark 

mvn

Definitely getting spark on cyl 3.    Bad injector. 

How hard is it to change? 

Mark 

212rowboat

Laugh if you will, but... KY jelly.  Just a little on the oring.. slides right in (yuck yuck yuck, but it does).  

Is your engine exhaust monitored or reconciled via temperature/maf/map and tables alone?  There will be o2 sensors of the exhaust is monitored .. that kinda how it's monitored.  

If so, you may need to replace them.  They're sensitive.  

The engine tosses fuel (indicated by high ltft reading as opposed to stft, which is to say of long term maxed the short term is already maxed and it can't feed enough) at the cylinders in attempt to adjust for the lean condition it means the other cylinders were stupid rich.  The engine can't discern which cylinder so it spits it at all of them.  And guess what that actual rich condition does to o2 sensors? Eats them alive.... 

But... im thinking it isn't monitored as if it was it would have known it was actually rich not lean... remember, the fuel trim readings are lambda and demonstrate what the engine is doing not whats wrong with it... if it was a high ltft it means the engine was throwing max fuel for a thought lean condition... if it's pulling fuel by pulling pulse (low stft/ltft) it's because it thinks it's rich.  When what the tables dictate what's going in and it doesn't reconcile what the o2 reads you get another code altogether- and it's either maf/map depending on the configuration or o2 sensor faults.  


There are two bolts holding the rail on... take them out and wiggle the rail free... a little KY (nothing works better.... I felt like someone was playing a joke on me sending me to drug store for it but it works... really well and better than anything else I've ever tried) on the rail side of the new injector amd the cylinder side of all of them on that bank.. slide them in, bolt them down... easy... make certain and pull the either ev1 or ev6 connector off that injector carefully... they fire on impedence and a spade slightly askew impacts the pulse tremendously.  A matter of fact, check that connection carefully before even pulling the injector out.  

212rowboat

For future reference, a short term fuel trim fault isn't a big deal... a long term is.   Crossing zero on both is optimum, meaning lambda is zero long term, and the short term finds itself adding a point or pulling a point constantly and "crossing" zero in only slight alterations as conditions change.  

Look at the basket on the injector closely... you may have debris and it sounds like you do... injectors are hardy little effers and don't fail near as often as we think they do/can.  

YYZRC

I had to remove the IAC to get to one of the bolts on the fuel rail but otherwise it was a very straight-forward process.  This was on a Merc V8 so maybe different from your Volvo.

mvn

Thanks Drew for your amazing knowledge as usual!

The Volvo V6-280-M engine I have has an O2 sensor on each exhaust manifold.  It is not a Cat engine that has 2 per bank.

I can't even see the fuel rails!

I'm taking it back to the dealer tomorrow for repairs as I have warranty.  I'll post updates as I get them. 

Mark

mvn

Dealer has been awesome!  They just called and confirmed #3 cylinder was dead.  Not the injector though..... A bad plug!  In all my years of playing with boats, sleds, atv's, cars, trucks, even small engines, I've never had 1 plug go south.

I'm happy it wasn't an injector after watching all of the YouTube videos of guys destroying fuel rails trying to get them out.

Water tested, 5800 rpm, 55 mph!  That's better. 

Tach is junk though. 

Mark