300xs Fuel Problem

[BlazerVA]

Ive gotta 2016 300xs that I had the tracker valve replaced last fall. Reason being was the rpm would jump around soon as the motor was started and has fuel running out of the midsection onto the lu. Ran great since then til this past Friday. After a couple of runs I started it up to take off and noticed a miss in the motor. Then it started to surge and had fuel in the water around the boat. Pulled it out of the water and checked the tracker again and it looked good. Replaced with a new one to make sure and same. I checked the schrader valve in the air rail and a fuel mist blows out. After research everything says the air rail regulator diaphragm cant be replaced. Why is this and has that changed now? If so who sells them? Could anything else cause this problem?

1. 1E053040
2. 2016/Mercury/300xs
3. 29p Bravo xs
4. 6k rpm max
5. Idle 3psi and WOT 18psi Water Pressure Readings
6. Smartcraft

[DewRonInc]

Injector service in canada did mine, Blake, but European marine might be able to here, they were backed way up is why I had to use Blake

[BlazerVA]

Were you having the same issue?

[DewRonInc]

Nope, I ate a dirt dauber. But blake completely disassembles and repairs and cleans injectors

[DewRonInc]

He has all parts to repair, it obviously has a rail issue or the regulator diaphragm has a tear in it

[EuropeanAM]

If the air pressure regulator has a tear/hole in it, there will be liquid fuel spraying from the atmospheric vent openings in the Air Pressure Regulator cover. Very straightforward.

"Guessing" at parts or problems like this is seldom productive. There are a number of things that could cause this sort of symptom- and it really is important to make sure that the "attempted solution" does not become another problem.

A good starting point is to check the Air/Fuel Pressures with Glycerin-dampened Dual-Pressure Gauges, and record results for:

-Idle

-Under Acceleration

-5/10/15 seconds after engine shutdown (restart for each period).

Note: Fuel VAPOR at the air pressure test port is NORMAL. Liquid, spraying fuel is NOT.

Some of the potential causes include, but are not necessarily limited to:

-Low air pressure

-Broken Reeds in air compressor

-Air leaks ANYWHERE in the system (including Direct Injectors, o-rings, hoses, regulator, etc)

-Fuel Injector or O-ring leaks (inside rail)

-Tracker Valve or Fuel Pressure Regulator Diaphragm

-Pulse Fuel Pump Diaphragms

-Overfilled oil tank (remote)

-Oil System Check valve problems (crankcase or others)

-Contaminated fuel

-Ignition problems (coil, plugs, wires, etc)

-TPS or MAP sensor problems

-Engine Reeds broken or damaged

-Debris in intake or compressor (especially yellow plastic caps or cowling blankets)

[DewRonInc]

What did you find?

[BlazerVA]

Exactly what i thought. Fuel Regulator diaphragm had a pin hole in it. swapped it out and everythings running good now.

[EuropeanAM]

Great to hear!

Did you double check your Air & Fuel Pressures after replacement?

[BlazerVA]

I actually took it over to a Merc mechanic since I didnt have the tool to reinstall it. They checked injectors and both the rails. Was told changing the tracker valve wasnt a big deal without the tool but the spring on the other 2 held heavier psi.

[EuropeanAM]

That's definitely an accurate statement. Especially the upper/air pressure regulator (approximately 95 psi spring).