2009 330 DA 496's Axius. I just got this boat the beginning of the year. After months of work (new bravo 3's, had to pull engines for new motor mounts, engine couples, flywheel covers, starters, cooling tubes, basically while it out replace it). Apparently previous owners maintenance was non existent. Besides lots of rust and corrosion on parts replaced engines run great (480 HRS). So first time out after about an hour port engine stopped and I couldn't get it started again. next morning started and ran perfect. So we looked at Gen 3 cool fuel module and found cooling passages completely clogged (these are known to have this problem). Got and installed a new complete module. Now engines always run perfect until we stop and anchor out. After sitting for about 30 mins port engine will not start seems to be vapor locked. Starboard engine does not have any problems. I do run generator which is installed directly in front of port engine and next to port engine fuel tank. So yesterday same thing happened I ran blowers and put a bag of ice on cool fuel module and after about 45 mins it started. I noted engine temp at 140. My mechanics say its vapor lock and I just wanted to prove that it was. In all my research online it seems like this was a problem with carb engines but not Fuel injected and with the Gen 3 cool fuel module. In the past they have installed a water pump to pump water thru engine for about 30 mins when its shut off to cool. Has anyone done this?
Vapor lock?
- Thread starter Rob WIcha
- Start date
Bayou340
Member
- Feb 26, 2018
- 53
- Boat Info
- 340 Sundancer, 2000
- Engines
- Inboard Mercruiser 7.4 MPI' with V Drives
I have a 2000 340 with V drives and have been struggling with this the last year or more. During the winter and the water is cool no problem. As soon as the temps increase the port engine will not start after running around then sitting for an hr or so. The port engine is impacted because its fuel pump sits inboard between the two hot engines.
I tried wrapping fuel lines with heat shield, no luck. Will try wrapping the cool fuel module with heat shielding next. Just waiting on it to show up. If this doesn't work I'm goning to have to go the additional fuel pump route.
I tried wrapping fuel lines with heat shield, no luck. Will try wrapping the cool fuel module with heat shielding next. Just waiting on it to show up. If this doesn't work I'm goning to have to go the additional fuel pump route.
scoflaw
Well-Known Member
- Aug 10, 2011
- 6,395
- Boat Info
- 1999 Powerquest legend 260 sx 502 mag
2005 Baja 242 islander 496
- Engines
- 502 mpi Bravo 1
496 mag B1
Running the return line back to the tank works.
I heard of people putting heat shield around fuel lines as a suggestion but haven’t heard of any results. That makes sense that port fuel pumps are between both engines so it heats up more. I put a temp gun all around both engines fuel pumps and both seemed to be same temp.
Running return line back to tank? You mean the line that runs back to the top of fuel regulator?
Running return line back to tank? You mean the line that runs back to the top of fuel regulator?
insfnds
Member
There is a check valve in the fuel system that keeps the fuel rail under pressure so it can't vapor lock. It may be part of the regulator, either the one on the cool-fool module which I assume you replaced or there is one on the fuel rail. This check valve should keep the fuel under pressure so it can't vaporize/vapor lock. The pressure will eventually bleed off but by that time the engine would be cool anyway. (FYI: I'm going by my 2011 496's - yours may differ.)
Another thing to try when it vapor-locks is to release the pressure at the Schrader valve on the fuel rail. Careful though as fuel and fumes will squirt out of this valve.
And don't confuse Schrader with Schroeder - he was the piano player on peanuts - or your friends will never let you forget it.
Another thing to try when it vapor-locks is to release the pressure at the Schrader valve on the fuel rail. Careful though as fuel and fumes will squirt out of this valve.
And don't confuse Schrader with Schroeder - he was the piano player on peanuts - or your friends will never let you forget it.
ColoSR
Active Member
- Apr 25, 2018
- 425
- Boat Info
- 2003 Sea Ray Sundeck 220
- Engines
- MX 6.2L MPI Mercruiser with 2.2 Bravo III drive
Your boat might be too new for this to be applicable, but mercury did have a technical service bulletin covering vapor lock in early 2000’s fuel injected engines. Troublesome engines got a check valve and a helper pump for when the fuel pump was filled with vapor. Link to a copy of the vapor lock TSB is below.
https://stu-in-flag.net/blog/wp-content/uploads/2014/08/vaporlock.pdf
https://stu-in-flag.net/blog/wp-content/uploads/2014/08/vaporlock.pdf
dan313
Active Member
Rob,
I've been chasing this issue for a number of years. I've had everything changed from Cool Fuel mod to fuel rails and injectors, (paint issue) Thought this would solve the hard start issue. But it didn't. On my 350 mag when I have the issue I do this. Move the throttle to a 3/4 idle position. Once it starts move the throttle back to idle immediately. This works every time.
I've been chasing this issue for a number of years. I've had everything changed from Cool Fuel mod to fuel rails and injectors, (paint issue) Thought this would solve the hard start issue. But it didn't. On my 350 mag when I have the issue I do this. Move the throttle to a 3/4 idle position. Once it starts move the throttle back to idle immediately. This works every time.
toddh
Active Member
I had this done on my 210 select. 2000 model. It solved the issue.
Update! I read through service bulletin and pulled all the fuel lines off and made sure there was no blockage or restriction. Reinstalled fuel lines making sure they were sealed up good. Last 2 times out it has started fine after sitting for awhile. I’m thinking maybe there was a slight air leak.
i have to say i never experienced or heared about m a vapor lock on the newer mpi engines with the cool fuel module and check valve .
that said i experienced running the bilge blower all the time reduces significantly the air temperature inside the engine compartment .
that said i experienced running the bilge blower all the time reduces significantly the air temperature inside the engine compartment .
