Rodbolt 17 please help!!

[mitch]

Arrow up when pumping primer so as one way valve closes properly.


seahorse 5 has the answer

[zenoahphobic]

I would stop the theorising and RIP out the tanks and lines and replace with two separate systems.
Costly and painful. There are people that would simply sell and upgrade. Manufacturers don't make things to last, guessing ethanol would have added to a great deal of deterioration.
Or if persist try pressurising tests that may inflate "collapsed" rubber components or reverse flush an "intermitted" blockage. My 2 cents

[zenoahphobic]

I might add, the design may have reached its limitation because of the legislative requirement to not let vapours to escape - simply difficult to have a closed system of liquid and gas (imagine fuel foaming by sloshing).
The limited life of components coupled with the age of the boat simply may be the straw on this camel's back!

[rodbolt17]

and it gets better here in the states.
hulls manufactured after January 2010 cannot vent vapors directly to the atmosphere and neither can vapor seperators.

the new rules blow but its what we get and have to figure out how to fix.

[dorado42]

Ok rodbolt17 I finally got to run the boat a couple of times with new relief valve on port motor. Boat ran sooo much better...the first two times (short trips only 20 miles offshore) no problems. The last trip I had the same problem again on BOTH motors. I had sat for about an hour fishing. It was the fifth drop of the day. When I took off the boat came up to speed but then fell off. The good news is I was able to just pump the primer balls (after the motors died) and the boat ran fine afterwards (pulled anchor and came home). My question is do you believe it could be the relief valve on top of the VST tank also need to be replaced. It was much warmer out today then it has been on recent trips, as well as the problem only occurred at the end of the day (the hottest time of the day). The first relief valve fixed the starting idling problem for sure. Eventhough the problem showed up it was not near the headache to get the boat going again. Please let me know what you think.

[rodbolt17]

dude
dude
dude


its a dirt simple hydraulic system.

over 120 posts?

the check valve between the VST inlet and the low pressure lift pump intake simply maintains 10 psi,or so, at the VST inlet.

once the VST needle closes and allows no more fuel into the vst the excess pressure(fuel) is recirculated .

the valve at the airbox is simply a VENT for the VST.

if the VST was empty and NOT vented you could NEVR put fuel in the VST.

its not a vapor lock, its not a hammer lock , its not even the muffler bearings.

what your describing is there was JUST enough fuel in the VST to get up and start going.
then you simply ran out of gas.

by pumping the primers ALL you did was refill the VST.

that VST is NOTHING more than a small gas tank so the HP pump can get a bubble free suction of fuel.

dude this aint rocket science, if I can do it I almost could train my cats to do it.

well, not my cats, they tend to wait on me.

maybe I could train the wifes Yorkie?
nope. that dog is seriously ADD.

all jokes aside.
your simply describing a low fuel level in the VST.

[dorado42]

thank you rodbolt17 and I have a ****er spaniel that is really dumb and can barely learn to sit....LOL. You have explained the VST in the past (thank you) and I was thinking if the relief valve on the top of the VST was not maintaining the correct pressure IN the VST tank that would cause "low fuel level in the VST" or is that not the correct design of the relief valve. If the relief valve allows the VST to vent and the relief valve is "bad" would the VST think it is FULL (due to it could not vent.) If not the relief valve what else would cause the VST to have a LOW FUEL LEVEL. I have already replaced the low pressure pump, checked the VST filter in VST tank, what else could it be.

[rodbolt17]

dude
you still aint got a picture of two DIFFERENT valves and system.
beer aint cutting it, BRB, gonna make a liqur drink and try again.

[dorado42]

ok rodbolt...(as usual) you are right I do not understand how the relief valves work. I was hoping the problem would be the relief valve by airbox, but I understand what you are saying that IF the releif valve was not functioning it would NEVER get fuel. If the motor was fine all day why would "develop" low fuel level in VST. I was thinking as FUEL gets hot it may be vaporizing in the VST and IF the vent was bad would allow it escape so that fuel level would drop. I understand that would be the same as a "vapor lock" which cannot occur. So what do you suggest to check next?

[rodbolt17]

made a drink, had a smoke, your wearing me out.
I am getting mad.
mad enough that I may ask something stupid.


however.

Yamaha calls BOTH those valves relief valves.
they do very DIFFERENT functions.

BOTH can be easily tested with a vacuum/pressure tester.

ok get in your HEAD.
the vst is simply a small gas tank that the HP pump draws vapor/bubble free fuel from.

how to we get fuel into the VST if it was dry?

we use the PRIMER bulb.

after that the primer bulb can be tossed in the creek,,, compliant with any and all EPA regulations.

ok. VST is full.
from here on out there are TWO fuel systems , low pressure and high pressure.
low pressure keeps the VST full HIGH pressure is on the injector rail but it relys on the VST being full.

low pressure consists of the connection from the liquid level in the tank to the low pressure pump inlet.
any malfunctions there can cause issues with the HP pump.

at engine speeds below 1200 RPM the LP pump[ runs 10 sec on 20 sec off.



you can acutally watch this in the filter cup.

this is con*****ed by the ECU, any fuel NOT put in the VST is routed via a 10 psi relief valve back to the LP intake.
that's the valve wire tied to the VST asy.

when your engine was built we could still vent some vapors, that's the function of that stupidly high priced valve at the air box.
its ONLY function is to Allow vapors/air to exit the VST only after a pressure threshold is met.

[dorado42]

rodbolt sorry to have made you mad....I truly am NOT trying to be difficult. What do you think would cause the VST to develop a low fuel supply problem at the end of the day, after being fine for the previous seven hours of the trip?

[Pas Bon F115]

I hate that you are having problems but I am enjoying the discussion!

[rodbolt17]

next time, just before you hammer down.
pump the primer.
if the symptoms disappear check for air leaks and that valve on the lift pump suction side.

you can watch the lift pump cycle by observing the liquid level in the fuel filter cup on the engine.
remember,below 1200 rpm its 10 seconds on and 20 seconds off.

[dorado42]

OK so IF I understand correctly how the system works.... the low pressure pump runs 10 seconds ON 20 seconds OFF (under 1200 RPMS) to fill the VST tank. The relief valve maintains 10 psi pressure to the low pressure pump to allow it to pump to VST. So WHEN the VST is at a "low fuel level" (and the motor less than 1200 RPMS the low pressure pump cycles 10 seconds ON 20 seconds OFF (until VST full?). I have replaced the relief valve on the lift pump suction side as well as the low pressure pump (still had the problem Saturday). Is it possible that IF the motor is shut off before the low pressure (below 1200 rpms 10 seconds ON 20 seconds OFF) pump fills the VST, this can cause MY problem. For example I put the anchor down and back the boat down to my spot and soon as I get to my spot turn the motors off (vesrus let them idle for 2-4 minutes) the VST is NOT full, therefore when I take off, the problem presents itself? Thank you for your help!!

[rodbolt17]

the reason for cycling the pump at low speeds is a few points.

at low speeds the motor simply cannot burn as much fuel from the VST as the lift pump can supply.
that would lead to the lift pump running at a near stalled condition all the time and generating heated fuel.

so the ECU cycles the lift pump below 1200 RPM.

typically when the complaint is : I hit the gas and it jumps up runs 100 yds and falls on its face and the fix for that is a simple pumping of the fuel primer.

typically its an issue with the lift pump relief valve or an air leak in the suction side.

could be a partially clogged filter between the lift pump and VST.
could be an incorrect float setting in the VST.

you have to keep the low and high pressure systems separate in your head.

the low pressure side simply tries to keep the VST full, once full and the needle closes all excess fuel is routed back to the pump intake via that relief valve that opens at 10 PSI.
this maintains 10 PSI into the VST inlet.
ALL that VST is , its a mini gas tank that the High pressure pump can draw a solid bubble/vapor free fuel supply.

The HP pump draws the fuel, boosts it to about 45 PSI to supply the fuel rail.

if for any reason fuel gets low in the VST,Especially at take off, it will drop rail pressure and bog down.

at rapid acceleration the injectors fire both synchroneously and asynchroneously AND rail pressure is boosted due to the vacuum drop on the fuel pressure regulator.

so for a period of time at rapid acceleration that motor will almost double its fuel needs.

once the VST gets low and the lift pump cant fill it fast enough it goes BLAAAAH