My turn for vapor lock

[moombahighrider]

I have the two pumps on my 08 lsv an I still get vapor lock.

It's just one pump plumbed into another, both mounted on the block. The heat transfer from the block creates the vapor lock when sitting for some time after a long run.

The best way to fix it would be to replicate how the newer boats are manufactured and get a fuel pump that is mounted in the fuel tank, so it stays cooler. I suppose an inline pump that is not mounted to the block and insulated from heat would work well, provided you remove the old pumps...

[barefooterh2o]

We repair inboard boats. Usually if the pump acts up, as above, during hot weather or hot soak periods, it means a new fuel pump is in order. You can get by for a while keeping the motor box vented or pouring cold water on the pump but typically it would need replacing. The pumps that are mounted in the tank, we found fair worse than the ones mounted in the engine compartment. When the fuel in the tank is 1/4 to half and you make a sharp turns, the fuel sloshes to one side and runs the pump dry for a second or 2. Over time it also ruins the pump.

[moombahighrider]

Barefooter, I hear what you are saying but a lot of our boats (moomba/ supra) have had this problem from the get go. My boat, for example, has done this when in hot weather since I bought it new from the dealer. If I have my facts correct, skiers choice/ indmar started putting two fuel pumps in our boats from 08 until they changed to an in-tank option, to combat the vapor lock problem. None of my previous boats (stern drive) had this problem like I and a lot of guys on here experience. Now maybe the fuel pumps are just junk, but I believe it has more to do with the location that the pumps are mounted and the ability for the engine heat to affect the pump housing and fuel line.

I don't have any mechanical knowledge like you do, it's just what I have experienced and picked up from others on this forum. Also, that is an interesting point on the in-tank fuel pumps- it never would have crossed my mind as a potential concern.

[moombadaze]

When the fuel in the tank is 1/4 to half and you make a sharp turns, the fuel sloshes to one side and runs the pump dry for a second or 2. Over time it also ruins the pump.

interesting, never thought about that, i'll now just make sure to never get low on fuel

[parrothd]

Same with running your car on empty, shortens the life..

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[rdlangston13]

We repair inboard boats. Usually if the pump acts up, as above, during hot weather or hot soak periods, it means a new fuel pump is in order. You can get by for a while keeping the motor box vented or pouring cold water on the pump but typically it would need replacing. The pumps that are mounted in the tank, we found fair worse than the ones mounted in the engine compartment. When the fuel in the tank is 1/4 to half and you make a sharp turns, the fuel sloshes to one side and runs the pump dry for a second or 2. Over time it also ruins the pump.

wouldnt this happen to a pump that is not located in the tank too? i mean regardless of pump location in a sharp turn if the fuel gets away from the pickup then the pump will cavitate. I would think the pump would have a harder time regaining prime the farther it is away from the fuel source. All modern fuel injected cars have their pumps in the tanks and I have never heard of problems in cornering situations

[moombahighrider]

I was wondering/ thinking the same thing, David.

[parrothd]

Google it..

http://news.consumerreports.org/cars...be-costly.html

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[rdlangston13]

Google it..

http://news.consumerreports.org/cars...be-costly.html

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My argument is not that cavitation is not bad for a pump, cavitation IS bad, I just do not see how a pump mounted directly at the fuel source could fair worse than one mounted say 5-6 feet away. I have also heard about pouring cold fuel from service station on a hot fuel pump that has not been submerged in fuel due to running the tank real low causing the magnets in the pump motor to crack, thus making the pump inoperable. In either case it is an unlikely scenario and I would say even less likely on a boat due to the fact that it is used far less than a car.

[sandm]

I know guys that autocross their cars every weekend all summer long. in an effort to save weight, they run with bare minimums of fuel and are not experiencing any greater failure rate in fuel pumps. this in a car that's getting tossed all over a short-coned track.

I agree with moombahighrider in that the supra I had experienced vapor lock for the last time in '08. after running the blower(and, not thinking about it, replacing the fuel filter every spring starting in '09) I never had an issue again and never replaced the pump, so I'm not sure that a faulty pump is the culprit. my experience, after being left stranded at a gas station in Price Utah on vacation are that pumps either work or don't.