Engine Turns over and fires but won't start. plugs oily. compression 120-125,

[axeman]

ser number 2BOO9989. 2013 250 pro xs. I have Removed plugs and tested compression.. plugs oily and wet. turned key on with kill switch hot and hear fuel pump cycle. No pressure on starboard rail schrader valve. I know it could be a myriad of things but what should I check next? It tries to start and stumbles and dies. It started one trip before it quit altogether. It started rough on that trip initially and no problems. Rough start on this trip..tournament, and stumbled and started after first stop and then nada at second stop. Good compression. I understand what the different pumps do, pulse, LPFP, and HPFP, but don't know what to diagnose first. Any help appreciated. FWIW, I have a motor sitting on a stand with #5 cylinder bad but all parts sitting there fully assembled so its easy enough to pull and replace parts. Just want to know where to start.

[DewRonInc]

No gas, make sure injector harness is in good shape first

[axeman]

Wouldn’t the fuel pump pressurize the rail regardless of harness? It cycles but the rail has no pressure. Appreciate your feedback. I visually inspected everything. Also, the schrader valve on stern side of fuel pump had no pressure. Not sure if that’s the purpose of that valve tho.

[DewRonInc]

well indeed, maybe restriction or rubber piece between high pressure pump and outlet of VST preventing fuel from getting there

[axeman]

I’m gonna wait for my buddy to come over. I’ve never messed around with an opti type fuel system. I have a shop manual but it’s all foreign to me.

[DewRonInc]

If u have a Manuel it should be straight forward, have u checked ur fuel lines and primer bulb, one way to check for fuel line degrading is to take filter out, look inside vst and check for debris from line, common problem

[JOE54]

0 pressure at rail = my first thought would be seal on top of high psi pump , bad about splitting

[mactlman]

0 pressure at rail = my first thought would be seal on top of high psi pump , bad about splitting

0 at rail on what test port? one port is air one is fuel- fuel on top rt looking at the engine from behind I believe and air is one lh rail

[JOE54]

yes stb top of rail is for fuel psi only , no fuel psi should ever be seen on air test port at key on or ever , remember were looking for fuel psi right now not worried about air yet , gotta have fuel psi at rail first

[axeman]

I have done some research and studied shop manual. I’ll rebuild pulse pump while at it. An look at it all and see where it leads. Thanks and keep the suggestions coming.

[JOE54]

when you pump bulb and fill vst you have bypassed pulse pump engine should start and run on fuel primed in vst ,= no rail psi =no fuel in cyls = no start , make sense???????

[EuropeanAM]

And to add- AIR PRESSURE is just as important (actually almost more important) than fuel pressure.

Your engines FUEL PRESSURE is "Air Pressure + 15 psi". So no air pressure = almost no FUEL PRESSURE.

[bmas13]

I had a similar problem recently and it turned out to be a problem with the air compressor reed plate. One of the reeds had broken off and was the source of my air pressure problem. On my 2005 225 ProXS there are four bolts on the upper left of the engine/compressor (when looking from the back) and it was a simple to remove them and check. If you do this, be careful of the gaskets on the plate as well.

[JOE54]

I had a similar problem recently and it turned out to be a problem with the air compressor reed plate. One of the reeds had broken off and was the source of my air pressure problem. On my 2005 225 ProXS there are four bolts on the upper left of the engine/compressor (when looking from the back) and it was a simple to remove them and check. If you do this, be careful of the gaskets on the plate as well.

did you have fuel psi at key on hmmmmm

[axeman]

I have checked pumps in VST and finally discovered Air pressure regulator on port fuel rail has hole in it. I know its not a "serviceable part" but I replaced it and it runs but my idle is a little rough. buying a pair of rails for a diaphragm failure seems extreme. I am getting it on a diagnostic to determine if I have a miss or whatever. Learned a lot. So have I messed up replacing the diaphragm, and is it possible the fuel pressure diaphragm failed too? And should I be concerned that a piece of diaphragm got into an injector?

[JOE54]

but they are serviceable do it everyday, messed up = NO , possible sure it is , doubtful the way seat is designed in regulator anythings posible though , are you getting fuel in air side still / fuel psi in spec and holding psi at key off or rapid bleed off ??? report back

[axeman]

Holding air pressure and no fuel in air side. I am just checking plugs and cleaning them here in a minute. The miss is there but not constant. its clear after a run for about 20seconds at idle and then I feel it. it hasn't died from it and I am getting full rpm at WOT...5950 at full speed69mph..

[JOE54]

possible plug fouled , how you gonna clean um ????