Fuel pump keeps failing Fuel pump keeps failing
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    Fuel pump keeps failing
from John-Helena #10343 #10343  
5/20/2012 11:04:43 PM


 I recently had a Yamaha dealer replace my 2003 90HP 2-stroke power head with a re manufactured unit. Soon afterward the fuel pump failed, The mechanic (best in town) said to loosen the 2 10mm bolts on the fuel pump then squeeze the bulb. If I see gas dripping or streaming out - then the diaphragm is bad. I did, it was, so I brought in the old one and bought a complete new unit (not just the gaskets.) The new one soon failed 22 days later, he gave me a free replacement. This morning, 20 days later - it failed again! (I use my boat about 3 days a week) It seems to fail on WOT which I seldom do. . any ideas on why these OEM (Yamaha Japan) pumps keep failing?

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   similar post last month from MikeF  5/21/2012 8:08:31 AM
 Another guy on here had an identical problem with his Yamaha fuel pump. It sounds like they may have an issue with their diaphragm.

   I've been having the same problem from fishintechnician #13154 #13154  5/21/2012 10:55:22 AM
 I have been having the same problem for the last six months.My boat would bog down and cut off at 4,500 RPMs. My mechanic seems to think its the ethanol in the gas. I spoke to yamaha customer service and they told me, anything that causes the engine to sputter can cause the diaphragm to fail ie: bad O2 sensor, plugs etc. I think that was all BS though. The same time I started to have problems, I started using Startron fuel additive and ring free. I've been assured that neither of these should cause the problems I'm experiencing. But I have stopped using startron and continued to use everything else just to see if that makes a difference. The O2 sensor was dirty. It was cleaned this time, which makes the third repair for the same problem in about six months. I got a diaphragm from my dealer and I placed it in a covered bowl of fuel treated with startron. I'm going to see if the diaphragm starts to bubble up and dilaminate the way it has been in the past. FYI I have a 05 250 OX66 and I only run 93 octane. I'll let you know how things go, if i figure anything out I can email you and I hope you will do the same. It sounds like the diaphragms are just bad! My email is tudvmjt@aol.com

   My conversation with Yamaha from fishintechnician #13154 #13154  5/21/2012 10:59:56 AM
  They said there are several reasons why the fuel pump diaphragms may be popping. the first reason was a bad O2 sensor which can cause the engine to sputter and the increased pressure can cause to diaphragm to pop. the second reason was contaminants running over the fuel pump diaphragms they also recommended I do not use fuel stabilizer if my boat does not sit long periods time. doing the winter when it does sit for more than a month he recommended that I just drain the gas tank... so the O2 sensor was cleaned this time along with new fuel pumps so let's see if that cures my problem. lastly he said the resistors that go on the end the spark plugs can also cause the engine to sputter which can cause increased pressure which may lead to diaphragm failure

   Bad resistor from G-manLA #11833 #11833  5/22/2012 7:44:42 AM
 I had a problem with my fuel pumps going and after the third set, my mechanic finally found that I had a bad resistor with a bad ground. Replaced it and no more problems.

   How can you check the resitors? from fishintechnician #13154 #13154  5/23/2012 10:40:43 AM
 Is there a way to check them or do you just have to change them?

   Don't Know from G-manLA #11833 #11833  5/24/2012 9:18:36 AM
 Not sure. I would mention to mechanic. Mine determined the resistor was not grouded properly and allowing a surge or too much amperage to go to the fuel pump causing the diaphram to pop. I may be explaining this totally wrong. All I know is he changed the resistor and the problem went away. Prior to that I could run my motor less than 1 minute and the low pressure pumps would fail resulting in engine shutting off at idle speed. It would restart and as soon as in idled down it would die. Went through 3 sets of pumps before he figured it out. Good thing is, I didn't have to keep paying for the pumps.

   problem solved from John-Helena #10343 #10343  6/11/2012 9:33:13 PM
 The problem was not my fuel pumps, but it was a very hard to find problem. The fuel pick-up tube was incorrectly installed and had become separated from the nipple on top of the tanks. Picture a straw with loose lips! I had enough siphon going until I got to around 1/2 tank, then the tube floated down to almost all air.



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