Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

[Basser1]

Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

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]

Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

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]

Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

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]

Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

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]

Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

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.

 

[Ray Neudecker]

Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

For the last 20 years, I have made it a practice on all hot rod bass motors and race motors to remove all factory lift pumps, block the hole in the intake and use a Blue Holley with a regulator set at 6lbs. This has eliminated the problems with expensive fuel pump replcements and the problems caused when they fail.
After one problem after another with fuel restrictions on my motor home. The last time it acted up in the middle of the desert going to Phoenix and I did the same on the side of the road and it has been that way ever since and still works great.
The motors you are discussing are larger and newer than most in this area but they don't come close to requiring near the capability of the holley.