View Full Version : Engine won't start when hot

07-21-2008, 03:06 PM
Starting last week my '06 Outback V has failed to start on 4 separate occasions. The engine will turn over fine, but will barely start to idle and die or just not catch at all. It seems to only happen when the engine is hot (recently pulled skiers/wakesurfers). However, on time yesterday it hadn't been used for hours and did it again.

If you wait 1/2 hour to an hour it usually starts up fine. Once it's started it runs perfectly. Anybody have this problem before?

07-21-2008, 05:27 PM
carb or EFI? Fuel pump mabye fuel filter? Couple of weeks ago mine was acting simalar to yours and turned out to be inline fuel filter.

07-21-2008, 07:52 PM
vapor lock? what's the ambient temp?

Wake Master
07-21-2008, 09:29 PM
If it is EFI you need 80PSI in the fuel rail for the injectors to open. It could be, the fuel filter, fuel pump, or vapor lock. If you have not had any problems before it is probally not a vapor lock problem but you should leave the blower running the entire time the engine is running to help pull out the heat. I would start with the fuel filter if it's time to change the filter and see if this corrects the problem. I have a 07 XLV with the 340 EXT-CAT exhaust and the extra heat from the cat. converters can cause vapor lock. I had this problem and the manufactures are aware of the issue. The dealer installed a low pressure fuel pump at the tank to feed the high pressure pump. This is the fix for the vapor lock problems.

07-22-2008, 12:43 AM
I have a 2005 Moomba LSV and have had the same problem since day one.
I think one of the issues is the entire engine compartment regardless of blowers running or not gets over heated and the fuel pump runs hot to start with. I live in Canada and we get a few days +30 C I.E. 86 F just a nice day on the water.
We normally run 8 hrs on a day like this but I can count on the engine failing after about 4 hrs. So first thing I found was put cold gas in and it runs fine. Next thing was pour cold water on the fuel pump it runs fine. Bingo Vapor lock. I did some measurements with my digital meter and discovered the returned fuel from the fuel tank was running around 38 C or 99 F. This seems a bit warm for gasoline considering the boiling point is 40 C. The fuel pump it's self at this point is too hot to touch and is measuring 55 C - 130 F. Thus the problem is we are putting Hot fuel back into the tank that we don't use as the fuel pump is the recalculating type. Now the compartment temperature combined with the return fuel temperature creates a heat cycle that keeps getting worse until the engine vapor locks or the gas tank explodes. What worries me is the flash point of gasoline is only 43 C - 109 F so how far are we from exploding in flames. So at this point I wrap a towel around the fuel pump and keep pouring cold water on it ever 15 min or so to keep the engine running. One thing I am going to try is to install a gas cooler using the lake water to cool the gas down before it gets to the fuel pump. This might help and I will keep you posted. To bad Moomba Supra can't figure this one out.

07-22-2008, 12:09 PM
I just had this problem in Lake Powell last week. Luckily I found Bill and Tony's boat repair in Page and Bill knew exactly what to do. He said that between the fuel tank and the fuel pump there is a check valve or a ball in the fuel line. If this valve is to tight, meaning if the pump has to work to hard to pull the fuel past this point the fuel pump will overheat and cause vapor lock. I have an 07 XLV. He made this adjustment and we ran just fine for 2 1/2 days on Powell with no problems at all. No parts to fix it just a adjustment to this valve.

07-22-2008, 12:16 PM
I posted this just this morning on the general chat. We went to Lake Powell this weekend. The first morning we went cruising to look for a spot to park the house boat. After cruising for 45 minutes and then returning to the dock the boat would not start. It would crank but not turn over. I called my dealer and he said it sounded like the fuel pump wasgoing bad and that it sounded like vapor lock. He told me to put ice or a cold rag on the fuel pump. I did this and it worked long enough to get us to the place we were going to put our house boat and then it would not start again. I started calling boat shops in Page to see if they had a fuel pump for my boat. None did but I luckily found the saving grace to our trip. Bill and Tony's boat repair shop. Bill listened to what was going on and told me it wasn't the fuel pump and that he could fix it in a couple of hours. I finally got it to start again with the cold rag trick and then got it to his shop at 6:30 PM. He said he would have it ready by 7:00 the next morning. I called him the next morning and he had it ready. The problem was a check valve of some sort between the fuel tank and the pump. The valve was making the pump work to hard to pull the fuel through the line and that was why the pump was overheating and vapor locking. $300 later and we finished the next two days without a problem. Many thanks to Bill at Bill and Tony's 24 hr boat repair shop in Page.

Dave A
07-22-2008, 03:00 PM
I leave my blower on all the time we are running. If the boat has been run and we are going to eat lunch, or take an extended bread, I open my engine compartment with the blower on. I had this problem once, but since I have take those steps, I have not had it again. For some reason I never had this problem on my direct drive, only with the V-drive.


07-22-2008, 03:19 PM
Thats because DD are better!!! :p

Wake Master
07-22-2008, 09:50 PM
This is the answer from an older post by Engine Nut

A little clarification. The issue we have been seeing that is presumed to vapor lock is a condition that appears to be most prevalent on the 2007 model 340 engines with ETX CAT manifolds. The theory is that the extra heat generated by the catalysts allows the heat to build up in the bilge after the engine has been run for a period of time and then shut off. After it sits for a while a condition called "heat soak" raises the temperature in the bilge and allows the fuel in the line between the pump and tank to vaporize. The high pressure fuel pump will not pump vapor.

That being said, you can reduce the possibility of happening on any boat by doing a few simple things.

First, make sure your fuel filter is clean. As the fuel pump draws fuel from the tank through the filter, it creates a low pressure (vacuum) in the line. The harder the pump has to work the more vacuum is applied to the fuel. Fuel vaporzes at a lower temperature when it is exposed to a vacuum.

Make sure there are no restrictions in the fuel line between the tank and pump. The best condition is to have as straight and short of a line as possible. Each bend in the line can cause the pump to have to work harder and increase the vacuum.

After a hard run, try to let the engine run for a minute or two before shutting it off. This will help "normalize" the engine temperature and remove as much heat as possible from the engine. It might even help to disengage the shift control and raise the engine RPM in neutral to pump more water through the engine before shutting down.

Leave the bilge blower on after the engine is shut down to bring as much fresh air into the bilge as possible. Also, make sure the bilge vent hose isn't blocked, restricted or even disconnected from the vent and that the vent isn't blocked externally. It is not a bad idea on a hot day to lt the blower run all the time the engine is running .You'll also want to make sure to turn the blower on well before starting (if you shut it off) to make sure things are cooled off. This is not an unrealistic thing to do ... how many cars do you walk by on a hot day and hear the fan running after tha car has been shut off.

Your boat is significantly different than a car. The bilge of a boat typically does not have a lot of air circulating around it unless the blower is on. Also, cars have their fuel pumpslocated in the fuel tank.This keeps the pump cooler and allows the fuel between thepump and tank to be pressurized whichraises the vaporization temperature.

Try buying fuel from another source. We recommend using gasoline from a "Top Tier" supplier. Yuo can find which suppliers sell Top Tier fuel by checking out the following site. http://www.toptiergas.com/

I hope this gives you a little insight into vapor lock. It is a condition that has been around for a long time.It can be very frustrating but can be prevented in many cases by following a few simple procedures.
Larry Engelbert
Indmar Marine Engines
"Send Ed Down Under"

07-29-2008, 02:10 PM
I Just wanted to share some info on this as well. I've been stuck on the water twice for what seems to be vapor lock. I have a 2007 Mobius LSV with the 325 HP MPI. Both times I was running the engine quite hard then shut down and about an hour later tried to start. After a tow in and plenty of time to cool, the engine fired up with no problems. When explaining this to the deal they said it was most likely Vapor Lock. So I'm going to try the suggestions and see what happens. Below is some great information I found online related to this topic. Basically my new rules are:
Gas: make sure its high quality
Open: Open the deck after a hard run to push some fresh air into the bilge
Blower: run this while the engine is on and a bit after I stop
Idle: let the engine idle 5 min after a hard run

Since I like acronyms and it kinda fits I'll call this GOBI. If I don't Go Bye then I'll use "Go to dealer and get many new parts that are covered under warranty"!

Below is a tech bulletin I found on the subject matter from another boat maker:

Gasoline Engine Vapor Locking
Under certain conditions, engines may experience a ‘vapor lock’ condition. The three most common complaints that vapor locking cause are:
1. The engine starts. When the throttle is advanced, the engine quits running and will not restart.
2. If the engine does restart, it quits when advancing the throttle to get the boat up on plane.
3. After running the boat and shutting the engine off for 1 to 3 hours, the engine does not want to restart.
Conditions That Affect Vapor Locking
Fuels containing alcohol and ‘winter grade’ fuels will cause vapor locking complaints to increase.
NOTE: The new ‘Reformulated’ fuels have the RVP (Reid Vapor Pressure) very carefully controlled. It will normally take several following conditions to make an engine ‘vapor lock’. These conditions include but are not limited to:
1. Type, formulation and RVP of the gasoline in the boat’s fuel tank or sold in the area. ‘Winter grade’ fuels sold from October through March in most areas have the highest RVP.
2. Engine compartment air temperature and its ventilation system.
3. Temperature and vacuum on the fuel that is being delivered to the engine.
4. The location of the fuel tank.
5. The boat’s fuel supply system. This includes Inside Diameter (ID) of fuel line and fittings, fuel line length, routing, bends or kinks and the clamps that secure it. Extra fuel filters, fuel manifolds, anti-siphon valves, shut off valves, tank selector valves and the number of 90 degree fittings used.
6. Engine coolant temperature.
7. How quickly the engine is shut off after running at cruising or higher rpms and how long the engine and engine compartment are allowed to cool off after use.
8. The outside air temperature on the day the boat is being operated.
Corrections That Can Be Done To Help Minimize Vapor Locking
Before looking at the customer’s problem as a vapor locking condition, make sure something else is not causing the running problem. Air leak in the engine or boat fuel system. Check the tightness of all fuel fittings and clamps. Check for a cracked housing where a brass fuel fitting is threaded in it.
1. Follow instructions below:
a. Find out what type of fuel is in the boat’s fuel tank. Fuels containing alcohol are more likely to vapor lock on hot days.
b. Find out what the RVP of the fuel in the boat’s fuel tank is. 11 to 15 RVP (cool to cold weather) fuel will change from liquid to a vapor at lower fuel temperature than 8 to 10 RVP (warm to hot weather) fuel will. Refilling the boat’s fuel tank with lower RVP fuel will decrease the chance of vapor locking. Fuels purchased in most areas of the USA from late September through early April will cause most of the problems.
2. Follow instructions below:
a. Over the last several years, engine compartments have been designed to be quieter. This is done by using an insulation material and by making ‘engine covers’ tighter. This can cause high air temperature inside the engine compartment while the engine is operating and for a period of time after it is shut off. This period of time is called the ‘heat soak’ time. The air temperature inside the engine compartment during a ‘heat soak’ will rise higher than during the engine’s ‘running time’. This is because there is no air movement inside the compartment and no coolant flow through the engine. Normally, the quieter the engine compartment is, the hotter the air temperature will be on the inside during the ‘heat soak’. The highest air temperatures during a ‘heat soak’ will occur 30-40 minutes after the engine is shut off and can stay at that peak for up to 1-1/2 hours. This greatly increases the chances of vapor locking.
b. Increasing engine compartment ventilation to move the hot air out of it during a ‘heat soak’ will decrease vapor locking. Other items that can help reduce vapor locking are: Letting an engine idle for 3-5 minutes before shutting it off. Open the engine cover to let the hot air escape. Operate the bilge blower to remove the hot air.
3. Follow instructions below:
a. Fuel temperature (at the engine’s fuel inlet fitting) and the amount of vacuum
required by the fuel pump to draw the fuel from the boat’s fuel tank can contribute to vapor locking.
NOTE: Carbureted and EFI/MPI models only: The Water Separating Fuel Filter can be removed from the engine to a lower, cooler location. Use a Coast Guard approved fuel line between the filter and the fuel pump.
4. Check to see if the fuel tank is in an area where engine compartment heat or sun can preheat the fuel that is in the fuel tank. Putting insulation between the fuel tank and the heat source can help keep the fuel cooler.
5. Follow instructions below:
a. The fuel supply system can be a major cause of vapor locking. Remove all kinks in any of the fuel lines. Move the fuel line to be as close to the bottom of the boat as possible to keep it in the coolest area of the engine compartment. Replace clamps used to support the fuel line with larger clamps if the fuel line is being pinched or constricted with the current clamp.
b. Reduce the total length of the fuel line to be as short as possible. Eliminate or reduce the number of 90 degree fittings used in the system to no more than 2.
c. Any anti-siphon valve or restriction that causes a higher than specified vacuum reading can contribute to vapor locking and other driveability problems. If the vacuum reading is too high, try a less restrictive anti-siphon valve or the Electric Anti-Siphon Valve Kit.
NOTE: An engine that has a vapor locking condition may show a very low vacuum reading. This could be a false reading because vapor can give a very low vacuum reading. Check the inlet fuel line to ensure that a good solid flow of fuel is in the line instead of a mixture of fuel and vapors. As a test only, use a clear plastic hose between the engine and the supply line to look at the fuel flow visually.
d. Going to the next larger Inside Diameter (ID) fuel line and fittings can help lower the vacuum and help correct vapor locking conditions. An example is shown below. 5/16 in. (8 mm) fuel line and fittings ID 5.5 in. Hg (17.8 kPa), too high. 3/8 in. (9.5 mm) fuel line and fittings ID 2.5 in. Hg (8.2 kPa), too high. _ in. (12.5 mm) fuel line and fittings ID 0.8 in. Hg (2.7 kPa), good.
NOTE: Engines with 3/8 in. (9.5 mm) ID fuel line and 15 ft (4.5 m) total length or less: Going to a _ in. (12.5 mm) ID fuel line will not give much improvement. Fuel systems longer than 15 ft (4.5 m) may see an improvement by going to _ in. (12.5 mm) fuel line and fittings.
e. Mount fuel manifolds as low as possible in the engine compartment to lower the fuel temperature or remove them if possible.
6. Follow instructions below:
a. Make sure that the engine has the correct degree thermostat in it. Replace with the correct one.
b. Keep fuel lines as far away from engine cooling hoses as possible.
c. EFI and MPI engines with the ‘Cool Fuel’ system should have the fuel cooler temperature measured after the engine is shut off. The coolant hose going to the ‘fuel cooler’ should not get much hotter to the touch after the engine is shut off for 10-20 minutes than what it is with the engine running. If it gets hot after the engine is shut off, hot water from the cylinder block might be siphoning back. Installing the Check Valve Kit will stop this backward water flow.
7. How quickly the engine is shut off after running at cruising or higher rpms and how long the engine and engine compartment are allowed to cool off after use can greatly affect vapor locking. To help the boat owner reduce their chances of vapor locking, suggest that they do the items listed under 2c.
8. Nothing can be done about the air temperature the boat is being operated in. By following suggestions outlined in 1 through 7, the causes for most vapor locking complaints can be greatly reduced.
9. If all suggestions 1 through 7 have been done and engine still does not restart after it is shut off, the Fuel Pump Kit can be used. This kit will help a vapor locked engine to restart. IT DOES NOT CURE VAPOR LOCKING! The engine may still bog on acceleration. Kit contains a low pressure electric fuel pump, Check Valve Kit and installation instructions. This low pressure fuel pump helps feed fuel to the pump in the cool fuel system.