what exactly is vapor lock

driordan007

Recruit
Joined
Sep 22, 2009
Messages
2
I received a response to mercruiser 3.7 stalls when warm. One mentioned a similar problem caused by vapor lock. What exactly is vapor lock and how do you trouble shoot it?
 

mkast

Lieutenant Commander
Joined
Nov 6, 2002
Messages
1,934
Re: what exactly is vapor lock

Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines.
It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system.
This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling.
Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude.
In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,364
Re: what exactly is vapor lock

check to make sure your choke is opening all the way.

They way I check for vapor lock is by taping a thermocouple up under the engine cover and I go for a ride. Engine bay temps should stay under 180. If they get up over 200 then vapor lock could be an issue.
 
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