Upgrades to reduce vapor lock? 2002 VP 5.0 GL-B

Misterbulbous

Misterbulbous

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Purchased my FourWinns H190 new in 2002. Running the 5.0GL-B carbureted engine and have never had an issue, never kept outside, never missed a scheduled maintenance, babied like my own child - roughly 300 hours on the engine. Idles fine, no "steady-state" issues, etc...

I cannot seem to overcome a nuisance issue with vapor lock. My situation is the same as described in so many other places...hour or two of cruising, sit idle to swim, start back up and idle for a minute or so and then has the occasional situation where the motor fumbles and dies when getting on plane. From there it's a matter of letting things cool down and/or cranking and cranking till it catches. Once it catches, we're off to the races again. It's not an "everytime" event, but usually at the most inconvenient time.

Before boating season begins for me this year, I've verified the anti-siphon valve is ok, I've sleeved the fuel line with heat shield, changed plugs (not that I suspect an electrical issue), confirmed my impeller condition and other cooling checks, cleaned the spark arrestor, and made sure the engine compartment is open and not stuffed with my wifes 10,000 towels, etc.

Question is...is anyone aware or implemented other countermeasures to make the system more robust? Fuel additives? booster fuel pump? etc?

(PS: I haven't verified the fuel pressure, but engine always runs fine other than this bog/quit problem when real hot out).
 

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alldodge

alldodge

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I don't think its vapor lock (VL). While many years ago (60 and 70's) there where things that were called VL in cars, but it was mostly a carb issue. VL happens to fuel injected motors not carbs. It happens because the HP fuel system (not low pressure) heat soaks and boils the fuel. The heat increases the pressure and turns liquid into vapor.

When the cranking is started and if motor fires up, the pressure is still there and no more liquid can come in because the pressure is to high. When motor cools down, pressure reduces and now liquid comes in and it fires up.

You have a GL-B and an electric fuel pump. When this happens I'm thinking the heat could boil out some of the fuel, but all of the fuel that does boil, will vent out through the flame arrestor or go into the intake. Once the motor is running again, the float will have dropped and opened the needle valve in the float bowl. With motor running the fuel pump runs and quickly replaces all the fuel in the bowl if any leaked/boiled out.

So I think you either have a fuel pump issue (not running, runs but does not pump when hot) or a carb issue. When motor does this pull the flame arrestor and see if the carb is dripping fuel. If not dripping, pump throttle and see if fuel squirts in. Listen and/or feel for the fuel pump running

Now if no fuel is seen and pump does run, and pressure is good, then it could be the needle and seat are stuck together and not allowing fuel thru
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Misterbulbous

Misterbulbous

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^ thanks for that detailed response. The last time this happened (last year), motor flubbed out-just like running out of gas. Cranked and cranked for about an hour, 5 miles from dock...getting late so call US tow. As they are arriving, I decided to take flame arrestor off. My wife pumped the throttle, fuel squirted into the bowl and it started right up with no hesitation, so I’m kinda thinking fuel pump couldn’t push fuel to the carb?

Correct me if im wrong, but electric fuel pump is just one “stage” right? That is...not a high pressure/low pressure combo.

Frustrating because engine runs runs fine otherwise. No problem starting and stopping for skiers or other short stops. Even starts fine when hot. Maybe just need to idle for several more mins before taking off.
 
Scott Danforth

Scott Danforth

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next time it happens, open the fuel fill cap. if you hear a hissing it is most likely a plugged fuel vent and teh fuel pump simply can not draw fuel against the vacuum of the tank. simple fix then would be to unclog the fuel vent

yes, fuel pump is either pumping or not for the low pressure pump you have for a carb. EFI motors have two pumps. a low pressure pump to feed the high pressure pump.
 
Misterbulbous

Misterbulbous

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Scott Danforth said:
next time it happens, open the fuel fill cap. if you hear a hissing it is most likely a plugged fuel vent and teh fuel pump simply can not draw fuel against the vacuum of the tank. simple fix then would be to unclog the fuel vent

yes, fuel pump is either pumping or not for the low pressure pump you have for a carb. EFI motors have two pumps. a low pressure pump to feed the high pressure pump.
Click to expand...

Thanks Scott. I ran up to Autozone and grabbed one of their rental fuel pressure test kits, but didn’t have the appropriately threaded adapters and the pressure gage probably lacked good enough resolution for low pressure reading...so, I may just make one up myself or just replace the fuel pump for around $100. In the meantime, I’ll check the vent. Thanks for responses.
 
Scott Danforth

Scott Danforth

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DONT REPLACE PARTS UNTIL YOU DO PROPER DIAGNOSIS

you can throw thousands of dollars against the boat and still not fix what is most likely an under $1 to fix problem.

you can get the fuel pump test adapter here on iboats and for $15 have yourself a fuel pressure test setup.

a new pump wont fix a plugged vent or sticking anti-siphon valve.

do the diagnosis first prior to wasting money.
 
Misterbulbous

Misterbulbous

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AllDodge said:
You need a vacuum fuel pump tester
https://www.harborfreight.com/Fuel-Pump-and-Vacuum-Tester-62637.html

Many just call them a vacuum gauge because there are very few carbs today. You will more then likely need to make up a tee fitting to connect to the carb.

Again, if it won't start, remove the flame arrestor (maybe after the gas cap) and pump the throttle to see if you see gas squirt in
Click to expand...

Thanks for that link. Was looking on Amazon and never even thought of Harbor Freight - which is about 3 miles from my house.
 
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