fuel pressure problem ?

[speedfever]

I have a 2000 centurion wake board boat with a 350 mag mpi and v-drive. Engine serial # OL394367. The engine started missing and popping back through the the throttle body when you try to accelerate. I changed the plugs (they were white, real white) and I also changed the distributor cap and rotor. This stopped the missing but the popping is still there. When I try to give it gas, it acts like something is holding it back and it will not go to full throttle. I checked the fuel pressure at the rail and it had 18 psi. I replaced the fuel pump and cooler (part # 861156A02). This did not help. I replaced the fuel pressure regulator( part # 807952A1). This brought the pressure up to 28psi. One book I have says the pressure should be 34 to 38, another book I have says 42. 28psi is still not enough. I took ALL of the fuel lines off, from the tank to the fuel rail and blew them out with a compressor. All of them were clear and nothing came out of any of them except clean fuel. I also blew out the fuel rail. The anti-siphon valve was also fine. I installed a new relay and checked voltage to the pump, all checked fine. Timing is also fine. The boat will go to full throttle now with the new pump and regulator (still only 28psi) but if you put it under a heavy load or try to pull a wakeboarder out of the water it pops through the throttle body. The 28psi is when the boat is idleing. I can put a hand operated vacuum pump on the vacuum hose going to the fuel pressure regulator and pull a vacuum on it, the pressure drops. I can unhook the vacuum hose from the throttle body and plug the throttle body and run the boat, the popping is not as bad. So after all of this,,,,, WTF...???? help !!!!!!!!!!!!! Also, I replaced the fuel filter, dumped the old filter into a bucket and there was 2 drops of water in the bottom of the bucket.

[firehawkcat]

fuel filter changed or water seperator filter changed

[speedfever]

Yes, new fuel filter/water seperator. (Dumped the old filter into a bucket, 2 drops in the bottom of the bucket.)

[speedfever]

This engine has the cool fuel setup. Does not have 2 fuel pumps.

[speedfever]

anybody out there, help !!

[TWIN-SPINS]

sounds like you still have a blockage some where,,,can you by pass the fuel filter for a test,,,

[bobsbillets]

Is it possible that the pickup in the tank somehow broke off inside? You could be sucking air/and or fuel. Your gauge would still give you a reading if there was some air in the system. Are you using a mechanical gauge and checking at the fuel rail or schrader valve? Also I didnt think throttle bodys ran that much fuel pressure? I have multi port and 45 is good on it.

[speedfever]

The fuel pickup in the tank is fine, not broken. I pulled a vaccum on all of the fuel lines and did not get any leakage. All of the fuel lines held a vacuum. I also put pressure on the lines with a compressor and checked for leakage. All fuel lines check ok. The gauge that I am using is a fuel pressure tester and you hook it up at the schrader valve. It is multi port injection.
I get plenty of volume when it is pumping, just not getting the pressure.

[zahndok]

Is the replacement regulator adjustable or fixed?

[stevesxm]

well.. it needs to be 42 as you note... and the sytem is pretty simple pump-reg-return... so only a few things could be true and you have checked or changed most. if it were mine i would start over in this order

1) screw a mechanical gage into the schrader port as opposed to using the scrader itself.

2) plug the return line and run a quick test... pressure should be very very high. if its still low, then it is a pump or regulator issue... sort of...

3) those pumps are made to push rather than suck ... now i assume the press used to ok or at least you think it was so it hard to think of what might have change but worrying about that later, my next test would be to get a container of fuel that i could gravity feed the pump with and run the test... the logic being that if the pump can't draw enough fuel for whatever reason then it can't deliver enough fuel... so if the gravity feed works then your problem is on the inlet side of the pump and if it doesn't then its the pump or something else down stream.

the regulator is just a variable orfice return... with no vacuum its a small hole with vaccum its a slightly larger hole so even if it failed completely i can't imagine the pressure being low...

i have a feeling you are going to find that the grav feed will fix it which will then send you off looking for the new problem of fuel feed to the pump... on mine i use two pumps... low press high vol to an accumulator that feed the cool fuel system... that way that pump never does anything but push cool deareated fuel and the return goes back to the tank.