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Old 07-01-2011, 11:29 AM
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Default Low Pressure Fuel Pump--Yamaha HPDI

So, as i promised, I have been looking to tackle the Low Pressure Fuel Pumps on my Yamaha 250 HPDI's for some time. I have tackled all of the filters, the VST, the HP pump mini mystery filters and have posted on here the DIY. For many of us HPDI owners and even fourstroke Yamaha outboard owners, my objective has been to help as many on here save a few bucks and hope that these posts ---pay themselves forward. I know many of you on here don't like to turn a wrench and that's OK...for those that do, even a limited knowledge of motors is sufficient. I would recommend that anyone doing any of their own maintenance get a copy of your repair manual for your motor---there are many cheap sources. The LPFP are a strange design---there isn't any electrical connections to them. They assist in pumping fuel to the VST and therefore, there are two basic hoses on each end that are tie wrapped on. One IN and one OUT. It is a sort of hexagon in shape (6 sides) and there are two for each motor (250 HPDI). These pumps are a like a diaphram with a valve type gasket internal, that helps assist the pumping of fuel to the VST. Usually a sign of needed LPFP is when the outbaord smokes alot above and beyond just a few seconds at start up. Also, when the motor idles rough or dies at idle. Another indicator is the primer pump ball taking forever to get hard. After replacement, mine got harder (Insert joke here). Regular maintenance of your outboard should include the replacement of these pumps - at somewhere around 300 hours. Without further boring the crap out of you, here are the basics: First, purchase the parts, about $35 each. Make sure you pick up the back of the pumps gasket---its black and has three holes (Pictured) and your gonna need four extra small zip ties for attaching the top and bottom hoses.




So, to start, remove the two screws and pop off the flywheel cover.



Your gonna need to remove the three screws that pass thru the rubber grommets on the VST tank. The VST tank is the metal tank right in front of oil tank that has hoses coming out of it. You don't need to disconnect any hoses, just loosen and remove the screws so you can move the tank a little to be able to get to the screws that hold the two LPFP.



Once you have it loose, then with a small sharp wire cutter--snip the zipties (careful not to cut hoses).



Each LPFP has two bolts at the bottom---they are the same size socket as the one you used to get the flywheel cover --so no need to get the whole socket set. Unscrew the LPFP and wiggle a little to get it off. Then, pull off the hoses from top and bottom and your done. Take new LPFP, put hoses on, ziptie and your done. Move to the bottom LPFP and repeat. Then, reassemble VST and replace flywheel. Lastly, go pump the primer ball til hard. Remarkably, mine got real hard very quick and stayed that way. The other motor (Not done) does not seem to hol the fuel as well and takes longer to pump hard.

Alright---its done TOTAL TIME TO DO IT: 42 minutes-- gonna test this weekend and give you some feedback! Next job --changing the oil in the HP pump---yes it has oil! HAVE A HAPPY FOURTH OF JULY WEEKEND and a special thanks to our men and women of the military for helping keep us safe!!
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Old 07-01-2011, 11:50 AM
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RnR, I can't thank you enough for posting these DIY's. They've been of IMMENSE help to me (I don't have much mechanical experience). Quick question - I have a 200 HPDI. Do I have 2 LPFP's as well, or is it just the bigger block engines that have two?
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Old 07-01-2011, 12:14 PM
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Depends on your year 200 HPDI and model---here is an 04 HPDI 200 that has two.

http://www.boats.net/parts/search/Ya...UEL/parts.html

and thank you for the kind words.
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Old 07-01-2011, 12:16 PM
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Awesome - that is exactly my model actually. I suppose I could've checked my manual, but I'm at work and don't have it with me. Thanks again and I will try to pay it forward as I gain more experience!
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Old 07-02-2011, 05:53 AM
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Note that there are special tie wraps for the fuel lines. That look like your normal ones bu if you look closely at the head, you will see a curved surface that allows the wrap to grab all the way around the hose. Regular tie wraps leave a little space and that can lead to a leak. So spend a few bucks more and get the fuel line tie wraps.
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Old 07-02-2011, 06:14 AM
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RnR- You are the Man!! You have saved me countless hours from trying to figure things out myself. Thank you for taking the time and providing us with these awesome posts and assisting in our issues.
QQ- Will the lpfp affect top end speeds? I thought the pump inside the vst was low pressure? My idle is a bit ruff(as expected for 2 stroke HPDi) and sometimes cuts out (mainly when cold or trolling too long)but not all the time. As you already know with your help I changed all filters since I have a loss of top end but still same issue.
Usually about 4-8 pumps gets the ball stiff.

Last edited by AlexisMarie; 07-02-2011 at 06:41 AM.
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Old 07-02-2011, 06:58 AM
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Dude, you should get some kind of tht award for doing these. Your DIY posts on the HPDI are great! I'm pretty mechanical, but I really like seeing the job done with real-life color pics instead of shop manual diagrams. Hey, you mentioned it and I do need a service manual for the 250 - where did you get yours? My HPDIs are at 400 hours now - all trouble free - with just "regular" fuel filter replacement...f/w separator, paper filter, metal canister, and vst...but this winter, with the help of your posts, I'm going to do the whole system. Thanks again!!
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Old 07-02-2011, 07:14 AM
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Thank you RnR, this is fantastic. This will be another addition to my regular winter maintenance. Like posted above, it makes it a lot easier to be able to see it in real time verses the manual. I still use the manual but can`t beat the real thing. Again thank you.
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Old 07-02-2011, 12:25 PM
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Quote:
Originally Posted by ryanwhit View Post
Hey, you mentioned it and I do need a service manual for the 250 - where did you get yours?
I bought one on eBay last week fro $10 + $4 shipping. Genuine Yamaha manual...not a Cylmer or CD copy.

Good write-up RnR!

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Old 07-02-2011, 01:04 PM
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Thanks so much for a great write up. On my stbd HPDI 150, some of the symptoms you mentioned are there (smoke/soft bulb/etc), took them as "normal". Will definitely jump on this one asap.

Can you list which parts you changed? On my particular motor, the following parts sound like they would be related to the rebuild, but they cost more than replacing the entire unit (6E5-24410-03-00)

http://www.boats.net/parts/search/Ya...UEL/parts.html

pn33 6E5-24471-00-00 DIAPHRAGM
pn34 6E5-24435-00-00 GASKET, BODY 2
pn35 6E5-24411-10-00 DIAPHRAGM
pn36 6E5-24436-00-00 GASKET, BODY 3
pn39 6E5-24434-02-00 GASKET, BODY
pn44 650-24431-A0-00 GASKET, FUEL PUMP 1

Thanks again, Alex
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Old 07-02-2011, 03:13 PM
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Quote:
Originally Posted by aa331 View Post
Thanks so much for a great write up. On my stbd HPDI 150, some of the symptoms you mentioned are there (smoke/soft bulb/etc), took them as "normal". Will definitely jump on this one asap.

Can you list which parts you changed? On my particular motor, the following parts sound like they would be related to the rebuild, but they cost more than replacing the entire unit (6E5-24410-03-00)

http://www.boats.net/parts/search/Ya...UEL/parts.html

pn33 6E5-24471-00-00 DIAPHRAGM
pn34 6E5-24435-00-00 GASKET, BODY 2
pn35 6E5-24411-10-00 DIAPHRAGM
pn36 6E5-24436-00-00 GASKET, BODY 3
pn39 6E5-24434-02-00 GASKET, BODY
pn44 650-24431-A0-00 GASKET, FUEL PUMP 1

Thanks again, Alex
I suggest you buy the entire pump ( about $55) and a new gasket ( about 3 bucks). I just don;t think it is worth the effort to rebuild the pumps.
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Old 07-02-2011, 04:55 PM
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It all depends on what parts are needed. And I enjoy turning wrenches.
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Old 07-03-2011, 12:06 PM
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I guess I'm looking for a diaphram rebuild kit, if one exists. Found them but for the smaller Yams.
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Old 07-03-2011, 07:04 PM
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Quote:
Originally Posted by aa331 View Post
I guess I'm looking for a diaphram rebuild kit, if one exists. Found them but for the smaller Yams.

http://www.amazon.com/Sierra-Interna.../dp/B000N9LFK2

Dont get the Mallory equivalent.

I have used this kit numerous times and it works great.
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Old 07-03-2011, 09:10 PM
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Wow

Ordering four (2 per motor) of the rebuild kits, plus the gasket (650-24431-A0-00).

Thanks!
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Old 07-04-2011, 08:57 PM
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Some results: Boat ran absolutely great for three days of use this holiday weekend! I do have an occassional stall during idle---not always, just during the first cold startup. Once motors are warm or in gear, it doesnt stall. It seems that it hasn't been cured of that and will be my next investigation. I once fixed that issue with spark plug boot replacement of a couple that were out of spec. BUT, any and all smoke is GONE and motors don't shake. My guess is that it could be the VST tank mid pressure pump has lost some life. It is a big ticket item, so I'm lookin into it alternatives. Ran 100 gallons through the motors with ring free and she topped out at 51mph, so she's running well.
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Old 07-15-2011, 10:51 AM
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Great write up.!

A quick test to see if the pumps are bad is to slightly loosen the bolts that hold them to the block and then pump the primer bulb a few times. If you get fuel leaking from them then the diaphragm is leaking and the pump needs replacing.
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Old 07-18-2011, 06:20 PM
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Thank you, very detailed. I have 04 HPDIs 150, low hours. Primer pump ball on stbd remains soft. I'm leaning towards a problem from bulb to fuel tank and not at engine. Planning to disconnect at output of bulb, pump, and check flow - I assume it should fill quickly and get hard. Yes? Otherwise, will have to do the gas leak check suggested above.
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Old 07-18-2011, 07:10 PM
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Quote:
Originally Posted by RocknReeln View Post
Some results: Boat ran absolutely great for three days of use this holiday weekend! I do have an occassional stall during idle---not always, just during the first cold startup. Once motors are warm or in gear, it doesnt stall. It seems that it hasn't been cured of that and will be my next investigation. I once fixed that issue with spark plug boot replacement of a couple that were out of spec. BUT, any and all smoke is GONE and motors don't shake. My guess is that it could be the VST tank mid pressure pump has lost some life. It is a big ticket item, so I'm lookin into it alternatives. Ran 100 gallons through the motors with ring free and she topped out at 51mph, so she's running well.
RnR,
Glad to hear your enjoying your boat as you should after all this work you put into the engine and the much appreciated time spent on these posts.
I beleive once the VST clogs enough where the engine will momentarily die thats enough to damage the pump. It wont kill it, but it will take some performance\life out of it. Thats just my guess since after digging into my memory bank countless times I remembered my VST was only clogged once and after I replaced it and all other filters it never ran like it originally did. I replaced the VST every year and it never clogged other then the first time. As mentioned previously, I will have the injectors cleaned(at end of summer) but I suspect I will ulimately end up replacing that expensive pump. This is when having 2 engines come in handy. I will keep you posted. If its running good enough for now, leave it alone and enjoy your summer. Happy Boating!
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Old 07-18-2011, 08:37 PM
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Quote:
Originally Posted by AlexisMarie View Post
RnR,
Glad to hear your enjoying your boat as you should after all this work you put into the engine and the much appreciated time spent on these posts.
I beleive once the VST clogs enough where the engine will momentarily die thats enough to damage the pump. It wont kill it, but it will take some performance\life out of it. Thats just my guess since after digging into my memory bank countless times I remembered my VST was only clogged once and after I replaced it and all other filters it never ran like it originally did. I replaced the VST every year and it never clogged other then the first time. As mentioned previously, I will have the injectors cleaned(at end of summer) but I suspect I will ulimately end up replacing that expensive pump. This is when having 2 engines come in handy. I will keep you posted. If its running good enough for now, leave it alone and enjoy your summer. Happy Boating!
Thx...I don't think its your HP pump though. It either runs or it don't. It could be the electric pump (2nd choice) or the injectors (1st choice). Here's a cheap idea to clearing out those injectors a bit: Try some Yamaha ring free plus---mix it as a shock treatment and then stick to using it. See if that helps get you back up to full performance.

In my case: I think that I have to simply adjust the throttle position sensor---do a link/synch. There is an adjustment made to the idle of your engines. Mine really need to be adjusted- out of spec 0.60. i think after all the filter changes, LPFP, and all I have done to clean up these motors, they simply have fallen out of idle spec. To do a TPS adjustment to spec. requires proper equipment---the Yamaha Diagnostic Software (YDS) and a familiarity with the link/synch screw adjustment. This, I will look into and get back to you all, as I have had numerous pm and emails on others having this issue. Seems that the poor idle problem for HPDI's is ubiquitous.
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