I was riding down the river today at 67mph and 5750 rpm's, when I lost some powere and went down to 63mph, and 5400rmp. When I got off plane to go
under a bridge, the motor quit. Would fire, but go dead. I got home and pulled plugs and measured 110 psi on all cylinders. Has the Air pump gone out?
Don
Model #1251P73bD
Serial#2B122096
2016 Phoenix 921 ProXP Mercury 250 ProXS
Did you remove the belt and check compressor pulley for lateral play? Also check the belt tensioner with an inch lb torque wrench should be able to reach 70in lbs before reaching tensioner limit.
_______
Phil
'09 Hewescraft ProV
'09 150 Optimax
^^^ Good advice.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Don, I removed the Tracker valve diaphram, and checked it. Good shape, but there was alot of trash on the back side where the spring is. Found corroded coil tip and plug wire not snapping onto plug. Removed the top flywheel cover and removed the belt. The compressor turns pretty easy by hand is this normal. The top exhaust I can feel air draw in and come out. Would thought there would have been more resistance on it. I replaced fuel filter and removed trash from the bottom of that area, drained both side of the Fuel pump housings with no water coming out. How do I check the Compressor, the motor will crank for about 2 seconds and idol really rough before it dies.
2016 Phoenix 921 ProXP Mercury 250 ProXS
Check the Fuel and air pressures using a pressure gauge on the schrader valves on the fuel rails (rated for at least 120PSI).
Air fuel pressure check is gonna be hard without it running. Also really need the Merc gauges for that. They're out there, just have to search for them. Don't regret buying mine AT ALL.
Best money spent will be calling Don and getting the *correct* shop manual. Best $100 I ever spent!Read mine so much I've had to glue it back to the spine.
I wouldn't even speculate here as to what it is, although I have my suspicions where I'd start.
How did the plugs look? That'll show you if you've got a cylinder misfire and/or fuel delivery/burn problem in an individual cylinder.
Has compression, then it's likely going to be fuel or air. Couple other diaphragms that can cause that problem. Gotten darned familiar with them as well.
Later,
Dixie Chicken
Plugs all nice even black no carbon or wet plugs when removed. Most pressure I was getting out of the fuel rail was 40 psi but that was only about 4 revolutions before it quits
2016 Phoenix 921 ProXP Mercury 250 ProXS
Don't need to have it running to see the initial pressure, just turn the key to 'run' and listen for the pumps to kick in.
Wouldn't do ANY fuel pressure tests without goggles!!!! (Yep, made that mistake too, even though I knew better!)
Did you connect to the test fitting at the VST? (the tank where the fuel filter is)
As per the manual:
"Connect the pressure gauge to the fuel pressure test fitting and turn the ignition key to the "ON" position. The electric fuel pumps will operate for about two to three seconds. The pressure should peak near 40~45 PSI when the fuel pumps are working, and should drop to 20~25 PSI when the fuel pumps stop working. If the pressure rapidly drops below 20 PSI there is a fuel leak."
Now for the high pressure reading, which is on top of the starboard (right) fuel rail.
As per the manual:
"Start or crank the engine for 15 seconds with the starter motor. The fuel pressure must be within the specified range."
Pressure on the top of the starboard rail, at the schrader valve = 108.1~110.1 PSI (high pressure fuel)
Air pressure with the above 15 seconds of cranking should be 94.3~96.3 PSI. (fitting on the port rail)
As you can see, there should be roughly a 14 PSI differential between air and fuel.
Plenty of places for a leak to happen though. Diaphragms come to mind. Also could include a failed o-ring in a fuel injector. (Happened to me after installing injectors that had been serviced.)
Easy o-ring check is to pull the rails back from the head, but make SURE the Direct Injectors (air injectors) stay in the heads. (Can hold them in place with a flathead screwdriver when sliding the fuel rails back.)
First make SURE the engine is in a 'no run' condition by removing the spark plug wires or plugs. Although still possible for a spark to ignite fuel, so assume proper caution.
Rails are pulled back from the head far enough (couple inches) to get a piece of paper against each injector.
Turn ignition ON, listen for the electric fuel pumps to fire up. Look for leaks (wet paper)
That could be a failed o-ring, and/or diaphragm. You should see NO fuel coming from either rail.
As well.... You could have fuel in the air system. Air in the fuel system. With the air/fuel gauges it's an easy test because you just push the release valve and look for fuel in the air test port.
Without that, you can remove the crossover air line (AFTER depressurizing both rails). Turn the switch to ON for 5 seconds, and look for fuel coming out of either rail.
Port rail leaks fuel. Could be Fuel or Direct Injectors on that side, fuel regulator (diaphragm) or the rail itself.
Starboard rail leaks fuel. Same thing as above, any injector on that side, or it could be a bad tracker valve (diaphragm).
There are Air and Fuel Volume Tests (which help you know your compressor output, not just it's pressure for instance). Basically, you pinch off the air and fuel discharge hoses (not both at once) and watch for a fairly instant jump to 120 PSI then release them. That'll tell you the "volume" of either is good. (Decent test of the compressor volume.) Needs to be running though to test that.
Disclaimer... I don't pretend to know 10% of what others here know. This is just general test procedures from the manual. Tests that I've done on multiple occasions, with enough success however to comfortably diagnose my problem(s) and get things going again.
The Optimax isn't as simple as the older carb engines, but it's still an engine. Best thing is it's not under the hood of a car where you have to bend over, stand on your head, and get all greasy to work on it. Heheheeeeeee
Good LUCK!
Later,
Dixie Chicken
Rotate compressor pulley by hand, does it build pressure and become difficult to rotate by 3rd revolution?Originally Posted by DiawaKid
_______
Phil
'09 Hewescraft ProV
'09 150 Optimax
I did not think it was that difficult to rotate on compression stroke
2016 Phoenix 921 ProXP Mercury 250 ProXS
By the third (3rd) revolution CLOCKWISE, it should be difficult to take it through the compression stroke with one (1) hand.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
UPDATE: Reed was broken in Air Compressor, part ordered. Found broken reed also
2016 Phoenix 921 ProXP Mercury 250 ProXS
I WOULD NOT RUN IT UNTIL FUEL SYSTEM, FUEL RAILS, FUEL INJECTORS, AND AIR INJECTORS ARE PROFESSIONALLY CLEANED AND SERVICED!
You will be rolling the dice on completely trashing the powerhead.
get in touch with Don.
I'm good, IF the piston had gone, yes I would have everything flushed. No debree, and have the piece that broke off.
2016 Phoenix 921 ProXP Mercury 250 ProXS
same deal with a friend. one reed pedal broke off, found all pieces. new compressor, 1 hour run time then blown powerhead. blocked injector. Mercury then shipped a fully dressed powerhead.
Best of luck!
If he was able to find the broken piece of the reed and retrieve it, it's likely that he will be just fine once he replaces the reed plate assembly. That is one of the few failures we see that seldom transfers debris.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
New Reed plate on today, Engine cranked right up. and idoled fine.
2016 Phoenix 921 ProXP Mercury 250 ProXS
that is exactly what happened to a friends motor. broken reed pedal from compressor, found the whole piece. Merc replaced compressor. Powerhead failure with less than 1 hour of run time.
Merc sent a fully dressed replacement powerhead.
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