F225 fuel system issue stumps Yamaha Tech

[boscoe99]

Good point. I have no fuel leaks/smell anywhere when squeezing primer bulb or when pump is running.
i can put a clear hose on the output it I guess..
I still don't understand why a brand new LP pump with no noticeable fuel leaks in the system cannot keep the VST full.

If it was electrical, wouldn't the 5 amp fuse blow? Never has.

A fuel leak is not the problem. The problem may be an air leak.

Think about disconnecting the hose at the outlet from the engine mounted fuel filter. The pump is running. It will be sucking fuel, not air. Once the fuel in the VST is used up the motor will stop running.

[Ljs3@mindapring.com]

Thanks everyone. Will try again tomorrow..

[Ljs3@mindapring.com]

Hooked up remote tank directly to T at inlet of LP and had same stalling issue. All fuel supply leaks are now eliminated. The only thing left is to replace all of the short connector lines. Do I have to buy them from Yamaha or can I make them? $150 for the set...

[rodbolt17]

and now I would test the lift pump, tee in a line and test the output pressure between the outlet and the VST inlet.remember that pump is two parts, an electric motor and a set of rotors. lose the coupler or stick the rotors and the pump motor operates yet pumps nothing.

[Ljs3@mindapring.com]

Lift pump is brand new.

[Nautical]

Disconnect the fuel line going into the VST at the VST Inline filter or run a separate tube to a glass jar. . See if you get flow (psi) into a glass jar. If you have flow going to the (jar)VST then it would appear the pump is good. Check for bubbles in the glass jar with the hose submerged.There are some pretty smart techs on here that will solve this for you. Take one step at a time. Maybe your pump is acting up, bad connection, intermittent operation.

[Ljs3@mindapring.com]

Thank you. I do still suspect an intermittent connection fault but can't find it,

[rodbolt17]

this is simply not that difficult.

its an electric inline blow through pump.
you can run the motor with the airbox off. just remember to unscrew the intake air temp sensor and plug it back in.

t into the pump outlet and the vst inlet.

hook up a pressure gauge capeable of at least 10 PSI.

at the pump connector, slip 2 straightend paper clips up the connector wires. tape in place.
attach a multimeter with gator clip leads or jumers with gator clips.

start the engine.
should read 12V for ten seconds then 0 v for twenty.
when reading 12V the pressure guage must show at least 7 PSI,10 would be better,
if the voltage does not cycle you have an electrical issue.
if it cycles with no pressure its a pump or fuel supply issue.
yep its about that simple.

[zenoahphobic]

Have we checked the fuse and wiring yet. Particularly at connections ( at new pump)?

[Ljs3@mindapring.com]

I checked all connections with a meter. Seemed to have 12v everywhere. 5 amp fuse has never blown.
New LP pump has new connectors.
I Put a stethoscope on Pump and can hear it cycle 10/20/10/20. What tells the pump to stop running, or does it just overflow through the loop?
Will try pressure Gauge again.
I know this should not be this difficult but it is really odd and maddening.
Thanks!

[Nautical]

Just because you have pressure reading doesn't mean the line is not blocked upstream,kinked or filter is somehow plugged. I would disconnect hose at the VST and actually see if you have a flow when the pump is on. You can jump the pump with a 12 v battery or turn key on ..check for flow using a glass jar.If you can keep it running by pumping the bulb manually then it has to be the pump as Rod says. You could still have a restriction that the manual pump is overcoming , but the pump is not able to. I have no idea , but I think those pumps only have 5-10 psi output and is a long shot, but you say that your technician is stumped..He has replaced just about everything.If you use the pressure gauge I would tee it in at the vst like the man says to.

[Ljs3@mindapring.com]

Removed all downstream hoses and clamps and the F filter. All clear, and hoses appear solid. no restrictions to fuel flow.
Could an air leak be coming from the vst vent lines/loop? If that air relief/check valve is stuck open/closed, would that be back feeding air into the fuel delivery loop or building up pressure in the vst? That is the only part I have not replaced. It appears to be functional though.
Am I correct that the LP pump does not operate at key on position, only when motor is running?
thanks!!

[CaribSurf]

Fuel pump issue

I had the identical problem on a 2002 TXRA 225 . Being an older engine, look for hardened hoses on the suction side of the lift pump, in conjunction with the plastic joint fittings being distorted- in particular the plastic fuel line joint on the small 90 degree hose elbow on the boat-side of the engines mounted fuel filter. Several hours on diagnostics then revealed a hair-line crack in this plastic joint , in conjunction with slightly hardened fuel hoses may be the result of the air getting into the system. It wont leak fuel , but will suck air. Hope you source the fault

[Ljs3@mindapring.com]

thanks. I'm replacing all hoses from LP into VST and fuel loop. However, I have the same issue even with remote tank connected directly to LP input T. Has to be somewhere within this loop.

[Ljs3@mindapring.com]

Had nothing to do with fuel or air leaks. Rebuilt entire fuel system, same problem. Has to be electrical. Bad relay or something somewhere.