Why am I getting Vapor Lock on my 4.3L

[kagr80000]

Well I thought I had this whipped last season but I guess not.
Have a 97 Four Winns 180 RX with the Volvo GL 4.3L in it.

Boat starts and runs great until we shut down and float for an hour or so.
Starts right up and under full throttle as soon as it gets to plane it just dies like it ran out of gas.( Vapor Lock)
Restart engine and let idle for a minute or so all is well agian.Engine is running 160 degrees when running and goes to 180 when shut down.

Anyone else have this problem or what else to look for.
Thanks Kman

 

[kagr80000]

Re: Why am I getting Vapor Lock on my 4.3L

Well Vapor Lock is out of the Question now

The problem is that the carb ( Holly 2BBL) is starving for fuel at take off.What I mean is after running on the lake for a few hours all is well.Its when we shut down and float for over an hour the fuel in the lines are draining back into the tank and apparently it's takeing to much time for the fuel pump to get everthing primed back up.
So when we start the engine and take off we have only 1 bowl of fuel in the carb and it dies.After cranking the engine for awhile everything is good to go until we shut down for over an hour.
This is what has been replaced:Electric Fuel Pump,Water/Fuel Seperator Filter,3/8" Fuel line all of it,Anti Syfon Valve at Fuel Tank also tank was removed and flushed.
So now after floating around we have to start the engine and wait 3 minutes before we can take off without having a problem.
It's strange I never had to wait before just turn key and go I must be missing something simple.

 

[Don S]

Re: Why am I getting Vapor Lock on my 4.3L

You forgot to mention the relay. It was replaced.
Seems you keep doing little posts about this problem and when you go to test it, you never get back. So you have a lot of information on a lot of posts. Put it all together and see what is missing.

 

[kagr80000]

Re: Why am I getting Vapor Lock on my 4.3L

Oh yeh the relay was also replaced and tested but it has nothing to do with the fuel line draining back to the tank.
The relay turns the pump on and off and the pump is working because the boat runs fantastic all day long.

 

[Don S]

Re: Why am I getting Vapor Lock on my 4.3L

Oh yeh the relay was also replaced and tested but it has nothing to do with the fuel line draining back to the tank.

And fuel is also not draining out of your carb and back into your tank. It would have to magically jump up through the air, through the needle and seat and past the checkvalves in the fuel pump and past the antisiphon valve to do that.

If there is no fuel in your carb, then it's because of an internal leak in the carb, or your accelerator pump isn't working making you think there is no fuel in the carb.

 

[kagr80000]

Re: Why am I getting Vapor Lock on my 4.3L

I disagree with your thoughts and this is why.
If the the fuel was leaking thru the carb there would be gas in the oil and I check the oil each time before we go out and there is not a drop of fuel mixed in it.(Nor Smell of gas)

We installed a glass inline fuel filter between the tank and the seperator filter so we could a look at whats going on and sure enough after sitting for an hour or so the filter was empty not a drop in it.So where did the fuel in the line go with the engine shut off back down to the tank not up to the carb.

As I said before the carb bowl does stays full the whole time while the engine is not running while where floating.It goes empty when we startup and leave. You can run for about a minute on 1 bowl of fuel on any carb engine or until the bowl is empty.

Going to check fuel pressure and suction on inlet on this new $240 electric pump again just to be sure.It seems the pump just isn't pulling the fuel from the tank fast enough.
We will see what happens and report back.

 

[Bondo]

Re: Why am I getting Vapor Lock on my 4.3L

So where did the fuel in the line go with the engine shut off back down to the tank not up to the carb.

Ayuh,....

Your tank Should have an antisiphon valve at it's outlet.....
If it Does,... There's No Way the fuel is going back into the tank...

 

[Don S]

Re: Why am I getting Vapor Lock on my 4.3L

It's not going back into the tank, it going back to the filter. If you could see inside the filter while the engine is running, you would see that it is NOT all the way full, it has to create vacuum in order to pull the fuel out of the tank, and the antisiphon valve cause it to pull 1 to 2" of vacuum.
When you shut the engine off, the fuel runs out of your clear filter (Which shouldn't be there), thru the electric fuel pump and back into the water seperating fuel filter under the pump.

It seems the pump just isn't pulling the fuel from the tank fast enough.

Any pump will put out a lot more fuel per minute than the carb can use. That same pump is used for a 7.4L engine.
You have changed the fuel pump with no change to your problem,

I still think you have an electrical problem in the fuel pump circuit. Could be the alternator not working right, are you having any charging problems?
When starting, your starter provides power to the fuel pump relay, after starting the power comes from the aternator. If it doesn't kick on right away, you don't have power to the pump relay, therefor, no fuel to the carb.

Rigging up a light that comes on would be one way of checking to see if the pump is actually running or not.

 

[kagr80000]

Re: Why am I getting Vapor Lock on my 4.3L

Allright just got out of the garage with a boat mechanic from Deep Creek and this is what we found.
After checking for the most common problems and checking fuel pressure from the pump everything looks good.
Then he hooked a Vacume pump to the anti Sypon valve at the fuel tank and started squezzing the triger unti the check ball opened on the valve.
It took way to much vac to open the ball off its seat so he said there was no way the fuel pump could pop it open the way it is supposed to.

I told him this is the 3rd valve I have put on with the same result.
Well now we drilled out the check ball and reinstalled the straight thru fitting and as soon as the engine starts within seconds the line and filter are full.Before it would take up to 1 min before the filter had fuel in it.

Well he said he believes this is the problem and it makes since after seeing it fill that fast but we won't know until we get it on the lake the next calm day on the warm water lake maybe next week.
If all goes well then I have to figure whats up with these Sypon Valves.

Will report back later

 

[chiefalen]

Re: Why am I getting Vapor Lock on my 4.3L

Did you ever check to see if the screen on the bottom of the fuel pickup tube is clogged ?

And maybe there is a lot of gunk in the tank.

Check the vent also, maybe causing a vacuum condition in the tank, not allowing the fuel to flow freely.

Really what i would do is run this boat on a external tank, that will pinpoint the problem.