f115 fuel pressure trouble

I recently cleaned my VST tank and replaced the filter. Now it seems that after it sits for a couple hours or more it is hard to start and I have no fuel pressure. It also seems that the issue is more prodominent if it sits with the motor trimmed up.

I replaced the gasket on the tank and seem to have it all back together tight. I don't suspect I have any leaks there but you never know.

Anyone have any ideas?

[Tucker]

By no fuel pressure you mean you pump the bulb and she lights up?? If so you definately have a air leak somewhere. All the fuel in the system drains back to the tank.

Ball is not completely soft and pumps hard with a few squeezes. I mean no pressure at the fuel rail.

[Tucker]

This is a real head scratcher. I'd pull the LP line off the VST and crank 'er up. If you have flow then it's got to be a problem with the VST. Where are the 4-stroke guys?? Don't you hate it when something turns to crap when doing routine maintenance!

[boats.net]

Recheck fuel hose routing, may have a hose too close to block and causing a vapor lock problem.

[cyrillefrenchy]

i would pull the high pressure fuel line and crank up, you should have high pressure and flow right away as the svt is supposed to be full.( be carefull not to spray fuel everywhere when you do this)
you can also try to see if you have fuel in the svt after a while by opening the drain on the bottom, try to measure the amont of fuel after running, and after it sits, compare the amont of fuel.
i hope this will help
frenchy

please excuse my ignorance, what is the SVT? I pulled the hose of the low pressure pump and it pumps gas when cranking. The filter bowl on the back of the motor also stays full. I will double check the routing but 99% sure it is the same as it was before.

Any other ideas?

Can it be vapor lock if it does it after sitting and the motor is cold? It has to sit for a period of time before I have a problem. Wouldn't it only be on a hot motor if vapor lock?

[cyrillefrenchy]

hello
i was talking about the "vst" and not the "svt"
sorry

[cyrillefrenchy]

i think the vapor lock is only on hot engine, not in your case.
again check if you have strong fuel flow on the fuel ram going to the injectors as soon as you crank the engine, and compare, cold engine , hot engine, after sitting for a while .. and let us know.
cyrillefrenchy

[Tucker]

If fuel is coming from the LP pump discharge it must be getting into the VST. I agree with frenchy, if you're not getting fuel from the HP line going into the rail, it's got to be in the VST. If you open the plug on the bottom of the VST and fuel comes out, the HP pump has got to be bad. There is a procedure somewhere on here to test the pump. I believe that puppy is expensive.

[cyrillefrenchy]

why did you pull apart the vst to clean it? was it dirty? usually replacing filters and draining the gas in the vst is enough during service maintenance.

I was dirty and clogged from the ethanol gas. I have drained my tank, replaced all lines, cleaned injectors and replaced the VST filter and cleaned the tank. After doing all that pumped the ball up firm it started right up. took the boat out and ran better then ever. Then after sitting at the island hard to start and ball a little soft. Finally got pressure and got it started. Try and start it the following morning to head out and same issue. No pressure at the rail and hard to start, After messing with it, finally get it to start. got out and runs amazing again. Hang at the island a couple hours and won't start when time to leave.

I believe the pump isn't running when I am having the issue because I can't hear it like normal. The pump was new last yr and I am afraid it might be the ECU. Either one is expensive and I don't want to buy either or if it isn't the problem.

[boats.net]

If you had a lot of bad fuel the fuel pump would be a suspect, the only way to tell is check voltage to pump and fuel rail pressure when it fails to start.

do I just test for 12 volts with my meter?
What type of readings should I expect?