Fuel Pressure Regulators - Maxum Boat Owners Club

iceman · 01-16-2012, 09:39 PM

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

pascavone · 01-16-2012, 10:59 PM

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.

seapuppy · 01-16-2012, 11:00 PM

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

ss3964spd · 01-17-2012, 03:02 PM

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

iceman · 01-17-2012, 05:19 PM

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.

iceman · 01-17-2012, 09:47 PM

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

seapuppy · 01-17-2012, 10:17 PM

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

GlennW · 01-18-2012, 01:07 AM

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.

ss3964spd · 01-18-2012, 05:56 PM

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 pump’s 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).

iceman · 01-18-2012, 07:40 PM

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

pascavone · 01-18-2012, 10:53 PM

on pre -2000 fuel injection, the ethonal would eat the rubber o-rings in the fuel injectors, on boats and on cars. So much so the nissan replaced all my car injected harness on an 11 year old car because of leaks and fires.

metal is not painted, that is in contact with fuel.

ss3964spd · 01-19-2012, 02:43 PM

Tom,

Our 2004 has an MPI engine with only about 182 hours on it. Has had nothing but ethanol blended gasoline in it since we've owned it and probably a good bit of it before we aquired the boat with 74 hours of run time. It has sat unused, winter after winter - 5 or 6 months at a time, with ethanol gas sitting in the entire fuel system. Sometimes the tank has been near full, other times only 1/3 full. We've never had a fuel system problem. Not once (Of course I'm sure I'll have to eat those words upon start-up this Spring!).

Like Pas said - no painted parts in direct contact with the fuel. I just cannot imagine that a fuel system designer/engineer would make such a specification. I'm pretty confidant that whatever your mech found in the screens isn't paint. Perhaps it's bits of one of the up-stream filters coming apart.

I did the same search as you and came up with the same info as you. Basically - nothing that supports paint in the fuel system. To the best of my knowledge there's only one point on an MPI equipped engine from where to measure fuel pressure - the valve on the fuel rail after the regulator. Just makes no logical sense that a blockage down stream would result in higher pressure on the fuel rail.

Regardless, whatever the true cause it sounds like you've got it sorted out now. Will be interesting to see what your flow scans tell you.

Dan

iceman · 01-19-2012, 03:43 PM

Dan,

All of that makes sense. Wish I could figure out where the "debris" came from. My fuel system worked fine for the entire 2010 season. Towards the end of that I had the Floscan installed. The problems started at the beginning of 2011. Maybe some junk got in the system during the Floscan installation ... or maybe I got some bad fuel at some point.

At any rate, I'm anxious to try it out, but I probably won't be able to splash it until April. I hope it's fixed, because this season I'm planning on some longer cruises, and better fuel economy will help.

Thanks for your help and advice!

Tom

shrew · 01-19-2012, 09:34 PM

I didn't catch what year the boat is. If it's pre-ethenol, then debris could be the inner lining of fuel lines flaking. It could be gunk from the tank. The Merc service bullitin seems to indicate debris from corrosion. I'd be more inclined to think the mechanic mistook the debris as beign paint. Maybe the corrosion in the bullitin is really paint overspray and they are trying to sugar coat it.

iceman · 02-27-2012, 09:53 PM

OK, I was thrilled to have good weather this past weekend and so I launched for the first 2012 cruise. As a result I have an update to this thread, and I'm happy to report it looks like the fuel system is indeed fixed and the engine is running like a top. I need to sit down and do some calculations from the chartplotter data, but from the Floscan alone, when on plane I was burning around 12.8 GPH at around 23 knots. Using advanced calculus, that works out to about 1.8 nm/gal or 2.0 mpg. This is pretty close to the fuel economy I believe I was getting in 2010, where last year the Floscan read between 14 and 20 GPH under these conditions. So, whatever the source of the problem, it appears fixed. I wish I understood the root cause so I could take preventative measures, but at least now I have a solid baseline to evaluate future performance against.

This weekend I took the family to Pier 39 in San Francisco, and stayed in a guest slip for 2 nights. SF is always hopping with action so it's pretty hard to get bored. Friday we watched the taping of a television show called "America's Got Talent". Saturday there was a "Polar Plunge" where folks dressed up in costumes and jumped in the cold bay water. That was a pretty wild sight. On the water, we cruised around Treasure Island near the Bay Bridge, saw some porpoises (?), and cruised through the Alameda Estuary. Flat calm water, so a very nice ride. Can't wait for the next chance to launch!

Tom

seapuppy · 02-27-2012, 10:37 PM

Tom
thanks for the report out....sounds like the bay really cooperated...we used to live out that way many yrs ago and always loved seeing SF bay....and the city.....I used to work at Mare Island navshpyd.....always interesting to say the least...

SP

ss3964spd · 02-28-2012, 02:20 PM

iceman · 02-28-2012, 05:09 PM

SP - yep, I'm familiar with Mare Island. My wife was born and raised in Crockett which is right on Carquinez Strait. One planned cruise this season is up into San Pablo Bay, where we would pass Mare Island on the way into the Carquinez strait, then we would berth at Benicia and hang out there for a day or two.

capav8r · 03-01-2012, 01:56 AM

I missed this post....Actually, I have first hand knowledge that the inside of the cool fuel modules are indeed painted. A co worker has an 05 four winns with the 6.2 MPI and had fuel problems. The mechanic discovered that the paint was coming off the inside of the module and had clogged the injectors, filters, etc. His boat had the classic symptoms of a bad anti siphon valve at the tank-when he would drop the hammer, the engine would start to come up, then starve after a few seconds. The boat was out of warranty, but merc decided to replace the cool fuel module and injectors for him. I would believe it either had I not went with him to the shop and saw it. It looked more like the casting was not masked properly and half of the interior was painted. There was a clear line where the paint was and where bare metal was. The mechanic told us that the "new" cool fuel module indeed addresses the paint problem and that merc does not want the public knowing that they replaced his module and injectors.

iceman · 03-01-2012, 04:09 PM

Capav8r:
Thanks for weighing in on this, I really appreciate it. This is the first corroboration I've gotten for my mechanic's diagnosis. Furthermore, It gives me a reason to call Mercury Marine and try to at least get the cool fuel module upgraded. I had to pay for two repairs that are probably both related to this problem - the fuel pressure regulator last year and the cleaning and filters this year. It just didn't make sense for an engine with less than 100 hours on it. Fortunately the invoice I have from this year specifically mentions cleaning out the paint debris.
I will post updates as I have them.

Tom