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fuel problem

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dhindelang

New member
I have a F150TLR 2006 Yamaha 4 stroke. It starts and runs fine for 5 mins under load. Then it fuel starves and spits and sputters. I have changed all hoses and filters except VST. It has two tanks and switching one to the other does not change anything. Also after it stumbles I can pull it back to idle for about a minute and it will catch up and run fine again for 3-5 mins. Checked the two low pressure pumps this morning and all seems perfect. No tears in any diaphragms or gaskets. After reassembling and running symptoms are exactly the same. I'm fixing to remove the vst tank and check that. Would a hanging float valve in the vst tank cause it to loose fuel and overheat? I changed the vst filter year before last. What is the most perplexing is why it runs ok and fails at exactly the same time. Any suggestions? Thanks. Doug
 
A hanging float could cause that, but I've never heard of that being a problem. I would replace the VST filter and the needle valve. If you find that the old filter looks fine when you remove it, then measure the fuel pressure within 3 seconds at key-on, and again after the engine starts. Those values should be somewhere around 45 and 38 psi respectively. If those aren't right, then check for leaks and check the pressure regulator (making sure the fuel pressure drops as you add vacuum pressure). It might be stuck.
 
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