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Old 01-16-2012, 08:39 PM   #1
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Default Fuel Pressure Regulators

Last week I took my Maxum 2600SE to my marine mechanic for yearly service. Some may remember the problems I had last season. I had a spike in fuel consumption starting with my first outing, from 12 GPH to 20 GPH. Back then a different mechanic found a bad fuel pressure regulator, and replaced it. That brought the fuel consumption down to about 14 to 15 GPH. I wasn't totally sure about the 12 GPH baseline since I hadn't had the Floscan for very long, so I let it ride that way for the season.

Last week the mechanic told me the problem again is high fuel pressure (60 psi) because of the FPR, and when I told him it had been replaced, he said there are two FPRs, one on the top and one on the bottom. He said there was some debris like paint in the FPR screen so he cleaned it out and it worked fine after that. He said the paint was some sort of internal coating that wore off. He didn't replace the FPR because he said it was a $1000 part and cleaning solved the problem.

The engine is a Mercruiser 5.0L MPI. So I have a couple of questions:

1. Are there really two fuel pressure regulators on that engine?
2. Has anyone ever heard of the FPR getting clogged by the internal coating wearing off? Why would that happen?

Thanks for any insight!

Tom
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Old 01-16-2012, 09:59 PM   #2
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12 GPH, on a 5.0 is not even enough to get it on plane, and running 16 mph..... plus people?
20 GPH on a 5.0 is running 32+, so Mr. Lead foot, what did you doing last summer?

Your electric fuel pump usually runs at 16 to 18 lbs.

You have a "fuel pressure damper" and/or "fuel pressure regulator" which is a $30 part that just evens out your fuel pump pulses.

I would guess your Floscan is installed in the wrong place on the gas line.

Any "debris" would be picked up by your fuel water seperator, and if your had debris, your fuel injectors would be really pissed off......

I usally get a tech on the telephone, and after listening to 3 or 4 diffrent shops, I can figure out the real story.
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Old 01-16-2012, 10:00 PM   #3
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Tom
as far as I know..there are only one major fpr's on the fuel system.....43psi at the pump.....1 is part of the cool fuel module...and you also have one on the fuel rail assembly....the one on the fuel rails drops the pressure to the injectors down to about 15psi...that one should not be affected....however the one before the cool fuel module has a filter element too it...so..that feasably could clog up...now ..the only way some paint got into the line is past the screen at the fuel pickup in the tank....you need to pull the tank cover where the pickup is and make sure the screen is still attached...you have a poly tank so..it's not painted....the chances of you getting paint flecks into the fuel system is pretty slim with that screen on...

SP
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Old 01-17-2012, 02:02 PM   #4
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Hey Tom, LTNS.

I am unaware of the MPI engines having two FPR's, and cannot fathom why two would be needed. They do have two fuel pumps though, the low pressure pump which then feeds the high pressure pump. From what I recall the MPI (individual injectors for each cylinder) engines have significantly higher pressure at the injectors than does the throttle body (TBI) system. The pump inlets might well have fine screens to catch any junk that got past the main filter(s).

Here's a Service paper that talks about testing fuel pressure. Note that it mentions only one FPR.

http://www.marinemechanic.com/merc/distributors/mercurymarine/sterndrive/electricfuelpumptesting.PDF

Regards,

Dan
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Old 01-17-2012, 04:19 PM   #5
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Thanks guys, appreciate the feedback. I think I'll call the mechanic and get a clarification ... maybe I misunderstood him. I'm very happy he thinks he solved the problem, and it wasn't an expensive fix. I'm just worried that if debris is getting into the fuel lines somehow that maybe something else is wrong. I'll check the tank pickup as Steve suggested.

Pascavone: the FLoscan is definitely reading correctly, since the gas fills match the fuel consumption it indicates. I might be mis-remembering about the 12 GPH (hope to launch and test that in a couple of months) but as I recall when I was up on plane, running about 20 knots on flat water, that was when I saw 12 GPH.
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Old 01-17-2012, 08:47 PM   #6
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OK I talked to the mechanic again, and I have some more details.

He says the problem was with the "Cool Fuel Assembly", which sounds like what SP wrote about above. That assembly has a "fuel cell" that is painted inside and out. He thinks the ethanol in gas eats away at the paint and it eventually broke away and partially blocked a screen in the fuel cell itself, and another screen in the main fuel pressure regulator. The second fuel pressure regulator is up above near the fuel rail, and that one was OK.

He thinks this will be an ongoing problem because of how Mercury paints the fuel cell. He recommended checking the fuel pressure every so often using a fitting on the fuel rail.

I've read alot of about problems ethanol-laced gas causes for boats, but this is the first time I've been (apparently) affected.

Thought I'd pass this along for any further comments. Does this all make sense, and is there anything I can do to avoid the problem? Be nice if Merc made a part that wasn't painted.

Tom
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Old 01-17-2012, 09:17 PM   #7
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aha...I was right then.....but the ethanol gas can cause problems....sorry to see your having issues with ethanol....hope this clears it.....

thanks for passing it all on to the rest of us....hope you have a safe and cheaper boating season coming up..


SP
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Old 01-18-2012, 12:07 AM   #8
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Interesting, I may need to look at this with my set up. I seem to be burning more fuel with one engine than the other. If memory serves me right I have put about $1100 in the starbord tank and $700 in the port tank in the past few months and I have filled based on the guage and not running the gen.
Something to look at when boating season slows down next month.
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Old 01-18-2012, 04:56 PM   #9
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I'd be shocked that Merc applies paint to the inside of any component that comes in contact with gasoline. Makes no sense to me whatsoever. Gas can soften, or eat away at, painted surfaces if left in contact with them without the aid of ethanol. I have never heard of any fuel system component being painted where the fuel comes in direct contact with that component. Of course, I've never taken a cool fuel (which evidently is needed because the two pumps impart too much heat into the fuel) assembly apart so I don't have first hand knowledge.

Regardless, if the screens were partially blocked I think that would result in lower pressure, or reduced flow, not increased pressure.

This from the PDF link above:

If the pressure is higher than specifications:
The pumps internal check valve may be stuck from fuel gum.
A defective fuel pressure regulator (EFI or MPI models).
Check for a pinched or plugged hose going to fuel pressure regulator (EFI or MPI
models).
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Old 01-18-2012, 06:40 PM   #10
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Hey Dan,

I agree, paint inside doesn't make sense. I did some searching on the web to see if this has come up for anyone else. I didn't see anything describing clogged screens, but interestingly, it turns out there is a service bulletin that says Mercury redesigned the Gen III cool fuel module in 2009. The redesign changed the inlets and outlets for the cooling water, as some people were getting corrosion that blocked the flow, but it didn't say anything about paint. I'm thinking of calling Mercury Marine about the paint thing. At any rate, it looks like I'll need to swap out that Cool Fuel Assy sometime in the future (to the tune of about $900).

I hear you about the pressure. Might he have been measuring it before the screen, instead of after it?

Tom
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