Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/17/84; site fred.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!qantel!lll-crg!seismo!hao!nbires!fred!childs
From: childs@fred.UUCP (David Childs)
Newsgroups: net.auto.tech
Subject: Re: Vapor Lock
Message-ID: <114@fred.UUCP>
Date: Mon, 25-Nov-85 15:36:38 EST
Article-I.D.: fred.114
Posted: Mon Nov 25 15:36:38 1985
Date-Received: Thu, 28-Nov-85 08:13:48 EST
References: <2922@vax4.fluke.UUCP>
Distribution: net
Organization: NBI,Inc, Boulder CO
Lines: 34

> Im sorry Randle but there is no such thing as "Vapor Lock" in today's
> automobiles.  Vapor lock originated with the gravity feed fuel systems
> of the Model T era because what would happen is the gas would get
> close to boiling and bubbles would form in the fuel lines and try to
> go up as the fuel is trying to go down.  The result was a stalemate or
> what is known as vapor lock.
> 
> Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
> could ever have any effect on it.  
> 
> Vapor lock tends to be the "scapegoat" when the mechanic can't solve
> the problem.  

What is a car of this day?  Porsche 914's of the 70's had vapor lock problems
that had to be fixed by the re-routing of the fuel line.  And a similar
problem occurs on the 1984/5 Trans Am, and Camaro Z-28 with the 5.0Liter
H.O. engine.  This problem cause GM to stop selling the HO engine.  The
GM problem is like vapor lock, but isn't exactly the same.  On warm days,
or in high altitudes, the carb has a fuel return line that open prematurly
because the gas vaporizes, thus encreasing fuel pressure, thus causing the
fuel starvation problem. I do realize that fuel starvation is a symptom
of vapor lock, but engineers can create the same problems with more hardware.

For anyone interested, owners of above said GM cars, the problem can be fixed
by GM (I think for free) by having them put a little fan on the carb to cool
the line to keep vapors to a minimum.  Other fixes are putting larger fans
that always run while the engine is running to keep the whole compartment
cooler, take off the trunk insulation, and put a plug in the fuel return line.
I don't suggest the last two, but I have had the last three done to my 84 TA
and the problem occurs about 1% as often as before.

					David Childs
					Integrate Solutions
"There's always time to scare the cat."