Mercury 175 EFI will not start when hot

[Jeff Schultz]

My 2001 Mercury 175 EFI starts quickly when cold, but after it gets warm/hot, it cranks, but will not fire or start. Cold or warm, it runs great after it starts.<br /><br />Any ideas?<br /><br />Thanks,

 

[The Marine Doctor]

Re: Mercury 175 EFI will not start when hot

This would be a problem that would be better diagnosed at a marine dealership.<br /><br />It's probebly something to do with the electronics...and is easily found with the DDT testing tool.<br /><br />Believe me...its not that I dont want to help you...but...I dont want to see any of the components on your engine ruined by poor test methods.<br /><br />TMD

 

[Jeff Schultz]

Re: Mercury 175 EFI will not start when hot

I called and talked to the local dealer, Clear Lake Boats, and they said it is probably "vapor lock", because it has been so hot and humid. Said I've been out early in the morning skiing and it's occured then too. They didn't seem to think it was a problem. They suggested waiting for cooler days. Would you agree??

 

[The Marine Doctor]

Re: Mercury 175 EFI will not start when hot

The pressurized fuel in the rail should still fire up. Mercury has addressed the problems of vapour lock by adding a VAPOUR SEPARATOR to the EFI and DFI engines.<br /><br />To my knowledge...the EFI AND DFI engines should not expirience vapour lock anymore.<br /><br />TMD

 

[Jeff Schultz]

Re: Mercury 175 EFI will not start when hot

Not knowing how a DDT testing tool works, is this something they can hook up to the an engine, run until it gets warm and see it, turn it off and see it. Can you please expand on the use of the DDT testing tool?<br /><br />I am not comfort with the "vapor lock" answer. I love to boat on "hot" days....<br /><br />Thanks in advance for your help!

 

[The Marine Doctor]

Re: Mercury 175 EFI will not start when hot

The Vapour Separator is the large holding tank for the fuel pump. Fuel sits in it prior to being sent to the fuel rail.<br /><br />The reason this is done is because fuel that is in a vacuum boils or bubbles at a lower point. So the VS is added to compensate for this by removing the chance of the boiling. The fuel is no longer in a Vacuum within the separator. From here an electric fuel pump pressurizes the fuel as it sent to the fuel rail and injectors.<br /><br />As for the DDT...the Marine shop should be able to hook it up to the EFI's computer and the computer will tell them what has failed. Or is not working properly.<br /><br />TMD