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Discussion Starter · #1 ·
just looking for more ideas and things to check, 2000 502 mag mpi - no VST it has cool fuel

I hooked up a Fuel pressure gauge and it is a constant 40-41 at all rpm's, boat will run 5-10-20 miles, then just die. It seems to stutter once a couple miles before it just dies, last time I was out the boat stuttered and the fuel pressure dropped to maybe 25-30, then ran Ok but I went in right after that happened.

After it dies the filter is not full with fuel when I replace it, I can change the filter and it will run for another 5-10-20 miles or so. I can even reuse a filter (pour out gas) and it will run just as long as a new one. No backfiring, or loss of power.

I dont think there is water in fuel,(at least not anything that I can see in a glass, no debris in filter (I opened filter up) It seems to me that it loses fuel pressure every once and a while.

Fuel pump was replaced in 05' (approx 140 hrs)

Just really bad gas? bad fuel pump? fuel regulator?
 

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Not Right said:

After it dies the filter is not full with fuel when I replace it, I can change the filter and it will run for another 5-10-20 miles or so. I can even reuse a filter (pour out gas) and it will run just as long as a new one. No backfiring, or loss of power.

Sounds like a restriction or issue before or at water separator. Your separator being somewhat empty means more is going out of it (to pump) then going into it (from tank.)

Again as said in separator thread, the outlet of separator to the pump is the center fitting which is a nipple fitting that extends down only an inch or so into the separator. Once fuel is used, you just have air space, although will still have vacuum and have slight pull on the inlet line from tank.

I would check the anti-siphon valve and also see if there is a filter or something on your fuel tank pick-up tube for some reason. MAybe kink or collapse of line from tank to seperator ?

Simply turning off the engine can cause a piece of 'something' that is stuck to the pick-up tube by virtue of psi/vacuum to 'float away' when the fuel system is shut off.

Remember the ping pong ball trick a bunch of years ago ? You'd drop one in someone's tank and at sometime (low fuel level) it would come over and seal off the pick up tube. Motor would die. Ball would 'float away' and then engine would restart. Then motor would die again not much later because ball would come back against tube ?

No, I never did it. I don't know if the ping pong ball trick actually worked, but the principal is valid. I was young when the older highschool guys where supposedly doing this. I'm a product of the 80's when fuel tank filler necks had the small opening in them for unleaded fuel nozzles. I was more into partially filling tires with water, but that's another story. :laugher:
 

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What CFM suggested is valid but if you want to cure the problem my friend had a problem with the fuel chiller causing vapor lock where we pull in and boat. The hot hole water temp is 95 degrees in the summer and the fuel chiller becomes a fuel boiler sort of speek. My port engine was doing this this year if I was out running hard and came in there and turned it off and restarted it within about an hour it would run for a minute and then stall. Im hoping my pickup tube issue was the whole problem but if it still does that Im going to install a Carter marine fuel pump in front of the water seperator fuel filter 6 psi, 72 GPH and tie the wires into the relay for the fuel pump already on the engine, I believe its fused with a 3 amp fuse. It took care of his vapor lock issue. The pump is $72 dollars through summit. If mine still vapor locks in the hot water thats the route im going. But I started digging when It stalled while running Sunday and not in hot water. Good luck.
 

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95 ? Wholly crap !

Just to make sure guys, make sure your inlet (from tank) fittings on seperator are tight. A small leak here may not show as a fuel leak but may let air in.

Yeh, that's why I mentioned possible updates and such on the other thread since Vapor lock and other issues I believe have surfaced on these set-ups.

PSI helps combat vapor lock wheareas the oppsotie is true ....less psi and of course worse vacuum lends itself to eaier to vapor lock.

As stated a million times, I really don't like the pump after the seperator deal. Packaging is easier I guess and protects pump against water contamination. But, it lends to pump cavitation issues from air and of course vapor lock.

Dang.
 

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I gotta admit Not Right, this has been a tough one to figure out, intermittent problems are the worse.

The only way I know to eliminate the fuel pump besides checking the pressure as you have done, is to do a volume check the 2 ways I mentioned in the other tread.. But it looking like you may have to get to that pick-up tube in the end, to check it out or replace it in order to eliminate that being the source of the problem, and go from there.

I don't know how the cooler is attached under the back seat, because I never really looked that close at it, but I'm guessing it's a PITA. I have the same thing under my Powerplay (pre-Powerquest), but my tank is in the bow.

And I have been wondering if you have a piece of debris floating around in the tank too, it's kinda acting like that, and just like CFM said, it gets sucked up, you stop, and it floats away after you remove the filter, but I doubt it's a ping-pong ball..

So try this next time it happens,,, just spin off the filter as you've been doing, but don't dump it or replace, just wait a minute and just spin it back on, and see if it starts up..
If that worked, then you definitely have something in tube or the tank, so have the tank pumped out, and cleaned out best possible..and replace that pick-up tube.
 

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Discussion Starter · #6 ·
thanks, I tried to get the anti siphon off the fitting aand ot wont budge, I cant spin the fitting with the barb on it because it hits the bulkhead. I would have to cut the bulkhead to get the pick up tube out. Next time I'll crack the filter and see if that works.

? - should I be able to blow into the tank past the valve? Isnt the valve supposed to be a one way valve? I can blow bubbles in the tank.
 

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I'm assuming you are saying that if you turn the 90° brass fitting that the aluminum straight barb fitting will hit the bulkhead.

The aluminum barb fitting has the check ball in it. Undo this from the brass 90°.

To be honest, I've never blown thru them back towars the tank, I have just removed them and that's it.

Thinking about it without testing, you should not be able to blow back into the tank thru it, of course unless it's stuck or if it's not there. If it's not there I'd question where it went and where it got lodged.
 

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Discussion Starter · #8 ·
the valve wont come off the fitting, the only thing that fits in there is a shorty open end wrench and it wont budge, I'm afraid if I try too hard I'll break the fitting off the tank. :dead1:

I would assume that the check ball would stop or make it very hard to pass air through, I can blow into it fairly easily.

The bulk head in the pic is what I would have to cut about 2-3" down and 3-4" across to remove the fitting, the sending unit also has to come out since the barb hits the unit to unscrew it
 

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You need a ratcheting wrench !!!! :D
If you don't have these, sounds like you don't, you'll again love life ! :D Support the brass with just holding a normal wrench slid into the fitting like you would turn it, but don't, just hold with some pressure.

BTW: if the aluminum fitting is on that tight then the factory could have tightened it too much, distorted it's body (it's thin aluminum so distortion would be easy to do) and then the ball started to stick at some point.

I heard it's common !

Again 'heard' cause I just remove these fittings without looking further into them. :laugher:

PSSST:
 

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Not Right said:
The bulk head in the pic is what I would have to cut about 2-3" down and 3-4" across to remove the fitting, the sending unit also has to come out since the barb hits the unit to unscrew it
So you are saying you can't remove the aluminum barb from the brass 90 NPT because something is in the way ? How do you get the rubber line in there then ?
I don't get it but my wife does call me stupid alot. :laugher:
 

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Discussion Starter · #11 ·
it's 11/16 dont know if they make those that big?

I'll try that, but you are forgetting that this area is 6" in front of my engine and the space is pretty tight, I can only contort my hands so much.

Thanks for your help, cfm
 

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cfm said:
So you are saying you can't remove the aluminum barb from the brass 90 NPT because something is in the way ? How do you get the rubber line in there then ?
I don't get it but my wife does call me stupid alot. :laugher:
He can't get the aluminum barb off and instead tried removing the brass 90 WITH the aluminum barb still attached. That's when it hits the bulkhead, when he tries to rotate the brass 90 around and around.
 

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Discussion Starter · #13 ·
I cant get the barb off the fitting. I can loosen the fitting from the tank but it wont spin 360 degrees because it hits the bulkhead and the sending unit.

I could try and cut the barb so it's small enough to spin the fitting out.

I cut the hose then pulled it off.
 

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t500hps - So....your on my wife's side are you ! :laugher:

A longer wrench will make it easier. In your case get a ratcheting one as I mentioned. The short knubby one's makes you think you are using too much force since you are used to the strength you use on a normal length wrench. :D The longer the wrench the less arm strength.

Also, the boats I've fixed sender units on and also removed the siphon valves on there has been a large round plastic access cover over them...all on the floor of course, sometimes under the seat where you can access it or even under the rug.
 

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Not Right said:

1)I'll try that, but you are forgetting that this area is 6" in front of my engine and the space is pretty tight, I can only contort my hands so much.

2)Thanks for your help, cfm
1) You should try to do it on my micro. You can't really fit in the engine compartment let alone get to the fitting. But I did it. And yes, the aluminum fitting was on real tight. Switched from short wrench to normal length ratcheting wrench worked like butter.

2) You won't thank me when it's not your problem ! :laugher: :dead: But seriously, if it is or isn't - you need to check to see if it is or isn't. Just one of those things.
 

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Not Right said:
it's 11/16 dont know if they make those that big?

Click here: http://www.sears.com/shc/s/search_10153_12605?keyword=ratcheting+wrench&gobutton.x=22&gobutton.y=8

You'll poop yourself with all the different possibilities. :D

The cool thing is with these ratcheting wrenches is because they are gear driven, you can unscrew things quickly even only if you have a few degrees of rotation.

I have a pretty good assortment of these now.
The one's I'm starting to really like are the offset one's with ratcheting mechanisms on both sides. Been real sweet on my snowmobiles that no normal hand can access things with normal wrenches. :laugher:

I can't tell you which style (length, straight or offset or curved, etc) you'll need for that job you have so you'll have to figure that out. Click on the link above and it will get you started with the decision making.

BTW: Chinamart (Wallmart) and K-Mart (sears tools since sears owns them) has some (not all) of these too.
 

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Pete,
I think you said you got fuel last at "one fish, two fish" area. Well so did Rick, and he is having somewhat similar problems too.
May be as simple as a really bad batch of fuel.

That said, I would still remove that fitting as described above.

I would also check your fuel tank vent (and hose) on the side of the boat to make sure it is 100% clear. It could be restricted just enough and while running, you could be drawing a vacuum on the tank. After you stop and fiddle around, vacuum is gone. When you resume running some more the vacuum is again drawn to stop fuel.

Next time it stops, get to fuel fill quickly and open it - listening for air leak while opening it.
 
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