Turd Polishing

[fishinwrench]

15 minutes ago, MrGiggles said:

 

Call me weird but I'd rather diag electrical than fool around with itty bitty screws and linkages on a carburetor

I do too, if the circuits are designed in such a way that "troubleshooting" can effectively be done.   

Dealerships with techs freshly trained in those systems...... consistently fail to diagnose and repair them properly.   

[fishinwrench]

Here's one for ya that should scare everybody to death......

A Merc 4-stroke with DTS (Digital Throttle and Shift) that SOMETIMES spontaneously revs to 4000+ RPM immediately after being shifted into reverse.  Foot no where near the hotfoot throttle.    

Nobody has figured out why.    And a recall hasn't been initiated yet.  

[bfishn]

8 hours ago, fishinwrench said:

...spontaneously revs to 4000+ RPM immediately after being shifted into reverse... 

Like this?

 

[aarchdale@coresleep.com]

keep the updates coming, not sure why but ive followed this whole thread and like hearing you an wrench go back and forth.  And a while back Giggles diagnosed my issue with my truck, new injectors and im all good.    Good mechanics are worth a lot... i appreciate both you guys. Wrench has helped me out a few times at no charge.   Im mechanically inclined but not at your guys status. 

[fishinwrench]

I'm interested in hearing how this one pans out also.    

I'll just tell you right now that I'm no fan of the design.   It makes no sense.

Why would an engine, that is supposed to be very light on fuel consumption, need an electric pickup pump?                     A simple mechanical vacuum pump should supply plenty of fuel to the vapor separator and boost pump, and it would take a pound or so off the finished weight of the unit. 

Needing 2 electric pumps just to supply fuel to 3-4 cylinders..... sounds grossly over-engineered to me. Somebody had a fart in their brain when they designed that POS. 

[MrGiggles]

6 hours ago, fishinwrench said:

I'm interested in hearing how this one pans out also.    

I'll just tell you right now that I'm no fan of the design.   It makes no sense.

Why would an engine, that is supposed to be very light on fuel consumption, need an electric pickup pump?                     A simple mechanical vacuum pump should supply plenty of fuel to the vapor separator and boost pump, and it would take a pound or so off the finished weight of the unit. 

Needing 2 electric pumps just to supply fuel to 3-4 cylinders..... sounds grossly over-engineered to me. Somebody had a fart in their brain when they designed that POS. 

It is stupid. Electric pumps suck at drawing fuel, especially this type. That is no secret. A mechanical pump and a needle/float would have made way more sense. 

And the fact that the lift pump is totally computer controlled makes it worse. Honestly I'm kind of leaning towards the lift pump driver in the ECM being no good, but I don't have any hard facts to back that up. It would be easy enough to bypass with a relay, but I'm not sure you could ever make the ECM live happily knowing it's not running a lift pump.

I guess it makes sense from an R&D standpoint since they can use the same FSM for all 75-135 motors, saves some money there. 

I'll take it out tonight and see what it does. 

[MrGiggles]

Just got back from a test run.

Took a while to get it to act up. Seems to run perfectly forever until you shut it down hot and fish for a while. 

It quit shortly after my first stop. No light, no power to the lift pump.

Next I checked the float switch. Ground on one side and 5v on the other. It's supposed to close and show 5V on both sides when the FSM is empty, however it was definitely empty and the circuit was open like it was full. Then I jumpered the float switch wires and the lift pump kicked in like it was supposed to, although it overfilled and set a vent switch code, which is normal since the float was bypassed.

I cleaned and tested that float switch probably 20 times in a jar a gas before, but I guess it doesn't really compare to being loaded and hot. There really isn't any moving parts to it, must have an internal magnetic switch, not much you can do there except replace it.

Hopefully that takes care of it, I'm starting to question my skills since I've "found the problem" three or four times now.

[fishinwrench]

If I just had an understanding of WHY they designed it that way, and the reason made sense to me, then I'd feel compelled to learn the system.   But IMO there are way less complicated ways to consistently deliver pressured fuel to the cylinders.    

 

[MrGiggles]

1 hour ago, fishinwrench said:

If I just had an understanding of WHY they designed it that way, and the reason made sense to me, then I'd feel compelled to learn the system.   But IMO there are way less complicated ways to consistently deliver pressured fuel to the cylinders.    

 

Cost savings and the ability to use the same FSM from a 75hp all the way to a 350hp Verado probably.

I'm not sure how well a pulse driven pump works on multi-cylinder 4 strokes, BRP made it work on a 2 stroke, wouldn't think it would be all that different. Looks like Honda, Yamaha, and Suzuki use cam driven diaphragm pumps to supply the VST. Other than a sticking needle and seat, not much to go wrong.

Mercury has had a lot of trouble with them, mostly float switch problems and the regulator hoses blowing, causing them to suck gas into the intake.

[MrGiggles]

New float switch took care of it. Ran like a champ tonight.