GMCforum
For enthusiast of the Classic GMC Motorhome built from 1973 to 1978. A web-based mirror of the GMCnet mailing list.

Home » Public Forums » GMCnet » The pause that makes you heart skip
Re: [GMCnet] The pause that makes you heart skip [message #70945 is a reply to message #70942] Sat, 16 January 2010 09:44 Go to previous messageGo to previous message
Steven Ferguson is currently offline  Steven Ferguson   United States
Messages: 3447
Registered: May 2006
Karma:
Senior Member
Very informative post Matt. Like I said before, I sure wish you could
do a complete data dump all at once so we could just archive it when
we need it.

On Sat, Jan 16, 2010 at 7:42 AM, Matt Colie <mcolie@chartermi.net> wrote:
>
>
> GMCWiperMan wrote on Sat, 16 January 2010 00&#58;31
>> By the way, how the heck can vacuum push gasoline to the booster?
>>
>> Ken H.
>
> Ken,
>
> As a friend used to say, "It is the perverse nature of inanimate objects."
>
> But to actually answer your question:
> A conventional carburetor does not actually vaporize fuel very well at all and in actual fact it spills a mixture of liquid fuel and air into the intake manifold.  (We often referred to the device our coaches have as a solid fuel carburetor in the lab to differentiate it from a gaseous fuel (like LPG) device.)
>
> The intake depression (vacuum) that is used to motivate so many things is temporary at best.  Its coming and going invites an unexpected (to some) number of issues.
>
> We expected (and on several occasions verified) that the liquid fuel would impact and stick to the interior surface of the intake runners.  That liquid fuel will then be right there at the manifold taps and waiting for any system pressure reversal.  A cold engine stall is a guaranteed "gotcha".  When the vacuum goes away (Map=30hg) the pressure in all those connected things is now lower than manifold.  All check valves can be counted on to leak to some extent at some time.  If it happens at the right time, there is wet fuel waiting to be sucked in.  Even if the check valve does not actually leak, the described pressure reversals will cause the connecting tubing to become filled with wet fuel.  We found wet fuel in the HVAC operators and transmission modulators.  I have seen brake boosters full to the check valve, but that is not common.
>
> A variety of popular Japanese car that was not fitted with power brakes in the home market had a very bad case of this.  The vacuum tube routing would cause the booster fill with fuel that would dump into the manifold when the brakes were released.  Since it also had an automatic transmission that was not used in the home market, the engine would stall.  As a contract house, we cured the "fire goes out when you try to go" by rerouting the brake booster's vacuum line and including a loop of steel line to trap fuel until underhood temps could encourage it to go back into the manifold.
>
> Fun stuff - Huh?
>
> Matt
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumiere (say show-me-air)
> SE Michigan
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>



--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

 
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Previous Topic: [GMCnet] QUARTZSITE 2010 pictures
Next Topic: [GMCnet] GMC still for sale in OR
Goto Forum:
  


Current Time: Sat Sep 28 17:29:22 CDT 2024

Total time taken to generate the page: 0.00674 seconds