PCM Vapor Lock (hoping Dom sees this)

[wingo812]

I tried to PM Dom Forte but the message didn't show up in sent messages; I'm trying this avenue as an alternative...


I've been surfing the site for a while now and have seen lots of threads about vapor lock and have a few questions...

I've seen all the stuff regarding "the mod" and that it is specific to the MP 6.0. I have a PCM 6.0 (2004 24V and motor is a 2004 confirmed by serial #) and am having the classic vapor lock problem. That is, the boat goes well and hard for hours as long as we don't stop for extended breaks. After a break, vapor lock.

The thermostat and temp gauge are new and boat runs at a normal temp (160-170ish). Things I've done: new bilge blower that I now run all the time; insulated fuel line from top of FCC to the fuel rail; changed fuel filter; I've checked all the cooling system related stuff (impellar, coolant, clear intake, etc., etc.) and it is clearly vapor lock.

First, any idea where the fuel is actually boiling? Does it occur in the FCC? My thought process is that if it can be determined where it is actually occurring then I can concentrate on keeping that cool. One reason why I think it is there (FCC) is that after the aforementioned break, the boat will actually start and we can go a little ways before the engine actually sputters and quits. My assumption is that what is in the rail is liquid and can be burned until the vapored gas reaches the rail/injectors. If the boiling is occurring there, I thought I'd figure out a way to insulate/cool the FCC.

Second, does your mod work in a PCM motor and if so, do you think it will cure my vapor lock problem? If so, can I get some detailed instructions for the PCM?

I'm sure you're bombarded all the time with this stuff, so I'm hoping you can take a few moments of your valuable time to help this complete stranger out! Thanks in advance and hope to hear from you soon...

Dan

[Stingreye]

I tried to PM Dom Forte but the message didn't show up in sent messages; I'm trying this avenue as an alternative...


I've been surfing the site for a while now and have seen lots of threads about vapor lock and have a few questions...

I've seen all the stuff regarding "the mod" and that it is specific to the MP 6.0. I have a PCM 6.0 (2004 24V and motor is a 2004 confirmed by serial #) and am having the classic vapor lock problem. That is, the boat goes well and hard for hours as long as we don't stop for extended breaks. After a break, vapor lock.

The thermostat and temp gauge are new and boat runs at a normal temp (160-170ish). Things I've done: new bilge blower that I now run all the time; insulated fuel line from top of FCC to the fuel rail; changed fuel filter; I've checked all the cooling system related stuff (impellar, coolant, clear intake, etc., etc.) and it is clearly vapor lock.

First, any idea where the fuel is actually boiling? Does it occur in the FCC? My thought process is that if it can be determined where it is actually occurring then I can concentrate on keeping that cool. One reason why I think it is there (FCC) is that after the aforementioned break, the boat will actually start and we can go a little ways before the engine actually sputters and quits. My assumption is that what is in the rail is liquid and can be burned until the vapored gas reaches the rail/injectors. If the boiling is occurring there, I thought I'd figure out a way to insulate/cool the FCC.

Second, does your mod work in a PCM motor and if so, do you think it will cure my vapor lock problem? If so, can I get some detailed instructions for the PCM?

I'm sure you're bombarded all the time with this stuff, so I'm hoping you can take a few moments of your valuable time to help this complete stranger out! Thanks in advance and hope to hear from you soon...

Dan

I would be curious about all your questions and answers.

I have the same motor and year. If surfing, I never have a problem restarting. At wakeboarding speed, if I shut it off, it will not restart unless I push the button on the throttle in and advance the throttle forward then crank. It will then start right up. Since I have been able to get it started with giving it throttle, I haven't bothered trying anything to fix it.

[wingo812]

We've tried that with no success. The last time it happened, it was after pulling teenage boys on tubes for a long period of time. We went to cove to chill and put tubes/ropes away so there was a period of time without engine running. Blower was on the whole time, but left engine cover closed.

[TeamAllen]

Mine isn't a PCM, like yours, but on the Mercs they added a second fuel pump closer to the tank to push the fuel. Until you get your answer, I might add to use marine fuel stabilizer to help counter act the ethanol. The trick that helped the most for me, prior to adding the new secondary fuel pump, was letting the boat idle for a minute after a hard/long pull to cool down a little before shutting it down.

[Ruger761]

the second fuel pump is key for TA and my models, never had an issue after I added it. Before once it did vapor lock I had to let it sit with the cover open for a bit and then cycle the key about every 30-45 sec for about 20-30 times until the pump primed back up, then it would start

[dom w. forte]

All the 6.0 are the same in the early years , these were emmision engines by design and were to get hot faster and remain hot , there should be a post on here from years back and it had pictures with the mod, but the mod blocks off the 1.125 refeed of coolant to the water pump and it flows coolant to the water pump from the hoses that either has a heater or a u shaped loop and this reduces the temp to a constant 160.

[dom w. forte]

Sorry for the response time but I had a busy weekend with a great Tige reunion here in fla,.

[Stingreye]

PCM Vapor Lock (hoping Dom sees this)

Wingo, if you do Doms fix on the Pcm motor please post back your results.

Thanks for following up Dom. Your help here is always appreciated! Hope the reunion went well!


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[TeamAllen]

Is this it?
http://www.tigeowners.com/forum/show...pcm+vapor+lock

[dom w. forte]

Yes thats the article.

[wingo812]

Been gone for a while myself, thanks for the replies. In addition to the vapor lock issue, I appear to have about 15 or so usable gallons of fuel in my 47 gallon gas tank. My theory is that the pump(s) while working are not working at full strength and that the fuel will gravity or suction feed until the level in the tank is level with the low pressure pump. I then have a motor that won't start so I fill it and it runs. It always takes about 15 gallons or so to fill it and then it will run again. Since the boat is used and 11 years old I've decide to replace both pumps regardless if they are really the problem or not; that'll give me some peace of mind and hopefully years of use without them failing.

If the pump(s) are indeed bad, could this also be a contributing factor to the vapor lock by not having enough pressure in the rail?

Thanks again in advance.

[dom w. forte]

Have you actualy looked at the tank and know it has gas in it , we had several boats over the years that the sender would get stuck in the middle and the owners thought they had gas but were on enpty?

[dom w. forte]

Just a side note Ive been working on a Nautique this week that the fuel pickup line in the fuel tank dissintergrated , when ordering a new pickup from Moller fuel tanks they asked if the owner was ussing Sea Foam , they indicated that the pick ups and floats will come apart with this product.

[wingo812]

There is definitely gas in the tank and I have taken the pickup out and inspected. I have used Sea Foam, but this was occurring before using it. It happens every single time I burn approx 15 gals...