Vapor Lock or Coil issue

[BIGALF]

My 5.7LXEFI MerCruiser has been having a major problem for the last year. It starts fine but after a 1 to 2 hour run and I stop the engine it will not restart until the engine is cold about 2 hours. It does everything that a vapor lock does but I can't seem to get it corrected. I increased the cooling inside the engine box by turning the blower on and running the engine at idle speed for 5 minutes before turning it off and lifting the engine cover.I also Added additional venting to the engine enclouser as shown on the attached pictures. I will try new fuel next time without any Ethanol alchol in it to see if that works. Am I in the right path or do you think it might be a electric issue, like a coil shorting out when hot or wiring break down under heat?

 

[bruceb58]

Re: Vapor Lock or Coil issue

What kind of troubleshooting have you done when the engine is in a no start condition?

Have you tried pulling a wire when you have your no-start condition to see if you are getting spark??
Have you pulled the plugs to see if they are wet with gas?

Ethanol is not your issue.

 

[Silvertip]

Re: Vapor Lock or Coil issue

Take a couple of big bath towels with you on your next run. When the engine fails to fire, soak the towels with cold water (or ice water in a cooler) and drape them over the fuel rails for five minutes or so. If it is vapor lock the engine should fire and run. If not, look for an electrical issue. Another way to test this is to build a cold-fuel can. This is a coffee can with about eight coils of copper tubing in it. Since your engine is EFI, the fabrication of this device needs to withstand pump pressure. The idea is to fill the can with ice and go boating. The ice keeps the fuel cool. The closer you can install it to the engine the better. This is obviously not a long term fix since you don't want to pull into a marina and have to say fill it with fuel and ice. It is a test fixture only.

When the engine does fire, does it act flooded and then clear out or does it just start normally as if nothing had happened. If it acts flooded, you might check the dip stick to see if the oil is contaminated with fuel from one or more leaking injectors. That may be the cause of the no start even though there is no fuel in the oil.

 

[Don S]

Re: Vapor Lock or Coil issue

I don't see vapor lock as being your problem. Since this has been going on for a long time (2009 thread), and it seems the only thing you have addressed is ventilation, I think it's time to do some real life testing.
You need to check the fuel pump pressure when it won't start, have the gauge hooked up so it will be easy and quick to read.
You also need to check for spark (as suggested by bruce58).

 

[BIGALF]

Re: Vapor Lock or Coil issue

Within the last 24 months every thing has been replaced or corrected from the screen in the fuel tank tube to the throttle body. New fuel pump, fairley new pressure regulator, new fuel/water filter. I will be rechecking for pressure loss and also spark. If it is not a vapor lock then why will it start up right after I turns it off for about 10 minutes but it will not start right up after it has been off for 30 minutes or more when the engine gets the highest level of heat sink to the engine?

 

[bruceb58]

Re: Vapor Lock or Coil issue

You could have leaking injectors. You need to determine spark and what the plugs look like when it doesn't start.

What does fairly new pressure regulator mean?

Like Don said, I would still put on a pressure gauge. Don't assume anything.

 

[BIGALF]

Re: Vapor Lock or Coil issue

The pressure regulator was replaced in Nov. 2006along with fuel injection nozzles. I will check fuel pressure and plugs. However, I will try the cheapest fix by using non ethanol fuel in my next 2 tanks and see what happens.

 

[bruceb58]

Re: Vapor Lock or Coil issue

I will try the cheapest fix by using non ethanol fuel in my next 2 tanks and see what happens.

And why do you think that could possibly matter?

The first thing you should do is the cheapest and check for spark and/or raw fuel on the plugs. Not sure why you are against trying that.

You can do whatever you want and chase your theories. Obviously, the dryer vent fix went well.

 

[BIGALF]

Re: Vapor Lock or Coil issue

Yes the dryer vent fix did work but my last tank of fuel was winter grade fuel with a RVP of 11-15 compaired to summer grade that is 8 to 10 RVP. All I want to do is first is use a better grade fuel and see if this is the problem. If it doesn't then I will pull the plugs, check spark and even check ignition coil or just replace the coil with a new one.

 

[Don S]

Re: Vapor Lock or Coil issue

If it doesn't then I will pull the plugs, check spark and even check ignition coil or just replace the coil with a new one.

You DO NOT have to pull the spark plugs to check for spark, just pull the center high tension wire out of the center of the distributor cap, hold it about 1/2" from a clean ground and crank the engine over and see if you get a bright blue spark. If you don't, well, don't just start throwing coils at it. Then you have to find out WHY there is no spark, and what part caused it to not have no spark. Quick note, it's seldom the coil.

Just assuming for a second it is a vapor lock, or caused by high temps in the engine compartment. For a test, why don't you take a trip, then, when you shut the engine off, open the engine hatch immediately so it can get plenty of fresh air. Then if it doesn't restart, you can just about rule out vapor lock.

 

[BIGALF]

Re: Vapor Lock or Coil issue

Ok will do what you suggest. If I don't get a blue spark when I try what you say what are the options to look at? The engine starts fine when cold.
The running process that I use is per Mercruiser service bulletin No. 99.7 which says run it at idle for3 to 5 minutes before shutting it down and open engine cover. The addition of my dryer vent and blower relocation was just an adder to get cool air flowing in the engine compartment. It was working fine until I let the boat sit for about 2 months this winter here in Florida and then put a tank of winter fuel with E10 Ethanol in it.

 

[Don S]

Re: Vapor Lock or Coil issue

It was working fine until I let the boat sit for about 2 months this winter here in Florida and then put a tank of winter fuel with E10 Ethanol in it.

Glad you finally decided to let us in on that little tidbit.

Do you have a Serial number handy for your engine?

 

[BIGALF]

Re: Vapor Lock or Coil issue

My engine is a 5.7LXEFI BR3 Ser.# OK022420. I think it is a model 457L111KS with 250HPand 350CID. The engine block was replaced with a remanufactured MerCruiser block in Jan 2007. Another story to be told on that mistake lated. What got me on the fuel issue track was reading an artical in www.fuel-testers.com about winter fuel,additives and fuel with and without ethanol. Everything from nozzles to screen to fuel pick up tube was replaced or inspected by a Mercruiser service mechanic who is suppose to be one of the best in central Florida.

 

[Don S]

Re: Vapor Lock or Coil issue

Everything from nozzles to screen to fuel pick up tube was replaced or inspected by a Mercruiser service mechanic who is suppose to be one of the best in central Florida.

Then, why are you here?

 

[BIGALF]

Re: Vapor Lock or Coil issue

What do you mean but that? I'm just trying to get someone else's ideas on what to do. Obviosly, there is no one path to look at so I'm just trying to narrow it down.

 

[QC]

Re: Vapor Lock or Coil issue

Ethanol is not your issue.

For reference for those following this thread . . . While I would normally agree when there are negative comments regarding Ethanol, I did have a vapor lock issue this last summer and believe Ethanol may have contributed. Here is an excerpt from a Mercruiser Service Bulletin:

Conditions Affecting Vapor Lock

 

[BIGALF]

Re: Vapor Lock or Coil issue

Took the boat out yesterday with a fresh tank of gas. I used upgraded special instead of regular. Did the extra cooling by running the blower before I stopped and lifting the cover. It worked fine let's see what it does when it gets hotter here in Florida..

 

[RANDE]

Re: Vapor Lock or Coil issue

Just curious to see if the fuel solved the issue. I've been experiencing the same thing on my 4.3L Merc. It appears (according to service bulletins) that the "cool fuel" system may need to have a check valve installed to stop back flow of heated water into the system that should be cooling it. What year is your engine?

 

[BIGALF]

Re: Vapor Lock or Coil issue

I had the boat out again Saturday May 7th. It was a hot day down here in Florida and I ran the boat up the ICW for about 2 hours and stopped the boat and restarted it with no problem. I think the extra cooling vents I did to the engine compartment and the new fuel (1 higher grade) and the fact that I put all new spark plugs on the engine was the cure. This is the cheapest thing to start with so you might want to try this out.The boat is a 1997 240 SeaRay Sundeck with a rebuilt 5.7 EFI engine replaced in 2007.

 

[BIGALF]

Re: Vapor Lock or Coil issue

Well I spoke to soon. Took the boat out today and there is still the problem. However, I don't think it is a vapor lock. I took off the flame arrester and saw a nice flow of fuel from the nozzles in the throttle body but is was a very ruff start. I had to move the handle forward and it worked beter then cleared up to a smooth running sound.
I think the spray is good but I can't be certain. It looked the same when I started it cold and it took off fine. Could it be something electrical that when it overheats it breaks up and when it cools down it works fine?