Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

[Basser1]

I have a 2003 Ox66 yamaha 3.1 225 with 350 hours. I have gone through 6 mechanical fuel pumps in the last 100 hours (changed all three twice) and now today I find I have one leaking again (the middle one). The other two are fine. I am wondering what is causing this? I have heard the diaprahms on these pumps frequently fail, but am wondering if another problem is causing these failures. The motor runs good, but when a pump goes I lose top end and have to drop the throttle back and then punch it to get it back. Change the pump(s) and it is fine until the next time it happens. This is getting expensive and I would hate to blow the engine if there is another problem causing a lean fuel condition.

[BruceAML]

What is the complete model number of your motor? What is the part number of the pumps that you installed? Are you using external tanks? What make?

[Basser1]

The model number is VX225TLRB. 2003 225EFI Ox66 VMAX. The pump(s) I am installing is 6E5-24410-03-00. The fuel tanks are internal. Two 32 gallon tanks, with a selector switch. The fuel line runs through a water seperating filter before it gets to the engine.

I have changed the water seperating filter annually and changed the filter on the engine last year. I also replaced the primer bulb with a genuine Yamaha bulb. I have never cleaned the VST filter. Could this be the problem? I can't find much on how the VST is cleaned while searching. I did see the seal at the top of the VST box is about 30$ to replace. Nice.

[JUSTINTIME]

running ring free?

[Basser1]

No, I don't run ring free, but I use Yamaha combustion chamber cleaner (de-carb) once per year and run high quality oil (Merc Premium Plus) and almost exclusively use Chevron (Techron) gasoline. Can I clean the VST filter with spray type carb cleaner or do I have to buy a new filter?

[JUSTINTIME]

buy a new filter

[BruceAML]

Yes you have the correct fuel pumps. Did you change the fuel filter element with a 65L-24563-00-00 element? Where are you located? Do they use ethanol in your area? Gas with ethanol goes bad in 60 days without adding anything to it.

[Basser1]

Yes, I changed it with the correct filter. I'm in Austin, TX. No ethanol here to my knowledge. I almost always use Chevron or Texaco gasoline. I have a friend that has been through nine pumps (same engine) in a few years. I am beginning to think this is just an engineering flaw with the diapraghms. I know this is a common problem with this engine. It is just strange that I go 200 hours and have no trouble, change out three, and then change three more 50 hours later and now have one more puking fuel.

[BruceAML]

Why not just replace the diaphragm instead of the entire fuel pump? The part number is 6E5-24411-00-00. All of the other parts to rebuild this pump are also available. Did you replace the fuel pump mounting gaskets when you changed the fuel pumps? The gasket is part number 650-24431-A0-00. Call up Yamaha customer service at (866) 894-1626. They open at 8:30 EST. See if they have any insight into this. Ask if there is a technical bulletin concerning this problem.

[Basser1]

Thanks. I also ordered a diaphragm kit ($16.00 vs 32 for complete pump), which I'll use for my next failure. The reason I haven't just replaced the diaphragm is a recommendation by Ray Neudaker (sp?). I think he posts on this board from time to time. He has always suggested replacing the whole pump.

Oh and yes I always replace the mounting gasket. To cheap not to.

Steve

[Basser1]

Just got off the phone with Yamaha. No service bulletin on this.

[rodbolt]

nope no bullitens on the lift pumps other than a redesign but nothing to do with the diaphrams.
run much with one leaking and you will post about lean piston burn or puking rod bearings thjough.
the 3.1L motors are rather hard on pumps for some reason.
try a fuel system vacum test. use the inlet at the lower pump. vacum should be less than 6"Hg at WOT, I would rather see about 4"Hg.
anything more and you have a restriction.
if the check valve is still between the fuel filter and the pump inlet then remove it.
no your VST has nothing to do with bad lift pumps.
is the diaphram disentagrating or just tearing?

[Basser1]

The last ones that leaked I took apart and looked and really didn't see anything dramatic. I am thinking they must be pin hole leaks. This newest failure I'll take apart and look very carefully. When I remove that check valve won't that siphon gas back to the tank? Ah, the tank should have a check valve. Once I remove that valve I assume a standard piece of fuel line will work?

[Basser1]

The check valve is still there.

[Basser1]

Took the leaking pump off and replaced it with a new one. Took the old one apart and looked for holes, tears in the old diapraghms. Couldn't see anything that looked like a hole or tear and I held it closely to a light. Just like the last ones I replaced. I'm a little baffled, other than thinking the gas is weeping through the diaphragm membrane. Any thoughts from those in the know?

I'm still wondering if removing the check valve is really somthing I should do.

[TCSavage]

If Rodbolt says to remove the check valve - do it!

[Basser1]

I assume he means number 8 on the fuel parts page, which they call a fuel feed assembly.

http://www.**********/parts/search.ht...0010%7C%7CFUEL

[TOHATSU GURU]

It sounds more like a diaphragm issue where it is losing its elasticity rather than anything else. Under these circumstances that would indicate either a bad production run on the diaphragms or chemical influence in the fuel. Or it could be Bush's fault...I heard he doesn't like Yamaha fuel pump diaphragms

[BruceAML]

Here is another thought. It is possible that all of the diapragms are bad because the pumps have been sitting on the shelf in the warehouse for a long time. What is the part number of the diaphragm kits that you have? Maybe these are newer stock.

[Salty Dog]

How can you tell when a pump goes bad?

[Basser1]

Symptoms: You'll lose top end briefly, then you can back off on the throttle and hit it and it will come back. I'll don't use full throttle much, but when I need it I want it there. I'll usually lose 4-500 rpms when a pump is bad and then get it back if I back off and punch it.

Off the water if you loosen the pump(s) from the block and pump the fuel bulb fuel will come out of the back of the pump. This is a closed fuel system so there should be no leakage from the pumps. Keep running a pump like this and your powerhead will eventually crater.

I thought the same thing the first time I bought pumps; that they must be old. This last time I purchased them from a large on-line retailer that does lots of business. Doubt they could be old.

[BruceAML]

The retailer that you bought the pumps from gets them from Yamaha Motors US. Yamaha in turn gets them from Yamaha in Japan. Yamaha in Japan gets them from the manufacturer. It is entirely possible that the pumps have been sitting in a warehouse for a considerable length of time. You might look at a pump and see if it has a date code on it.

[Basser1]

Will do. I'll take a look. I have heard that they did change the diaprahms on these pumps. How you tell, I don't know.

[rodbolt]

dont know about any date codes, there was a tech bulliten many years ago but its not applicable to anything in the past 15 years or so.
I think the latest pumps are -04 but the -03 will work.
be aware that the 3 small screws tend to loosen once the 2 6mm mounting bolts are tightened. before condemming the pump add nuts to the screws,tighten and retest. most will leak without tension on the 2 6mm bolts.
your symptoms actually sound more like a VST filter issue.
the diaphrams tend to get pin holes at the 3 and 9 0clock positions.

[snowmon]

have a 2000 250ox66 and been running new fuel since 06. been thru all the bs and found the anti siphon valve was all f'd up. b4 i found this i changed fuel filters (engine and remote) no luck. i actually ran a second feed off my tank to my remote filter and when this worked i checked out the check valve and found tiny grains of crap that looked like beach sand. it was stuck closed. i think this killed a few sets of lift pumps but i also think the achohol is contributing to the problem.