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Re: [GMCnet] The pause that makes you heart skip [message #70942 is a reply to message #70930]

Sat, 16 January 2010 08:42

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

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GMCWiperMan wrote on Sat, 16 January 2010 00:31

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 - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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[Message index]

		The pause that makes you heart skip By: jtblank on Tue, 12 January 2010 01:49
		Re: [GMCnet] The pause that makes you heart skip By: Steven Ferguson on Tue, 12 January 2010 05:38
		Re: The pause that makes you heart skip By: RF_Burns on Tue, 12 January 2010 07:45
		Re: The pause that makes you heart skip By: Matt Colie on Wed, 13 January 2010 07:51
		Re: [GMCnet] The pause that makes you heart skip By: Mike Kilroy on Wed, 13 January 2010 08:35
		Re: The pause that makes you heart skip By: jtblank on Thu, 14 January 2010 02:55
		Re: The pause that makes you heart skip By: midlf on Thu, 14 January 2010 03:17
		Re: [GMCnet] The pause that makes you heart skip By: jimk on Fri, 15 January 2010 09:18
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Fri, 15 January 2010 17:40
		Re: [GMCnet] The pause that makes you heart skip By: jimk on Fri, 15 January 2010 20:50
		Re: The pause that makes you heart skip By: Duce Apocalypse on Thu, 14 January 2010 10:46
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Thu, 14 January 2010 19:42
		Re: [GMCnet] The pause that makes you heart skip By: Bob de Kruyff on Fri, 15 January 2010 20:29
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Fri, 15 January 2010 21:28
		Re: [GMCnet] The pause that makes you heart skip By: Bob de Kruyff on Fri, 15 January 2010 22:36
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Fri, 15 January 2010 22:45
		Re: [GMCnet] The pause that makes you heart skip By: Bob de Kruyff on Fri, 15 January 2010 23:13
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Fri, 15 January 2010 23:29
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Fri, 15 January 2010 23:31
		Re: [GMCnet] The pause that makes you heart skip By: Matt Colie on Sat, 16 January 2010 08:42
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sat, 16 January 2010 09:12
		Re: [GMCnet] The pause that makes you heart skip By: Steven Ferguson on Sat, 16 January 2010 09:44
		Re: [GMCnet] The pause that makes you heart skip By: Steven Ferguson on Sat, 16 January 2010 07:04
		Re: [GMCnet] The pause that makes you heart skip By: mike miller on Sat, 16 January 2010 10:52
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Sat, 16 January 2010 13:38
		Re: [GMCnet] The pause that makes you heart skip By: Matt Colie on Sat, 16 January 2010 13:46
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sat, 16 January 2010 16:28
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Sat, 16 January 2010 17:01
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sat, 16 January 2010 17:16
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Sat, 16 January 2010 21:28
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sun, 17 January 2010 07:35
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Sun, 17 January 2010 07:38
		Re: [GMCnet] The pause that makes you heart skip By: bumpersticker on Sun, 17 January 2010 14:20
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sun, 17 January 2010 15:40
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Sun, 17 January 2010 17:33
		Re: [GMCnet] The pause that makes you heart skip By: Kosier on Sat, 16 January 2010 20:58
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sun, 17 January 2010 07:38
		Re: [GMCnet] The pause that makes you heart skip By: USAussie on Sun, 17 January 2010 07:40
		Re: [GMCnet] The pause that makes you heart skip By: Steven Ferguson on Sun, 17 January 2010 07:53
		Re: [GMCnet] The pause that makes you heart skip By: GMCWiperMan on Sun, 17 January 2010 08:36
		Re: [GMCnet] The pause that makes you heart skip By: Dennis S on Sun, 17 January 2010 09:37
		Re: [GMCnet] The pause that makes you heart skip By: Dennis S on Sun, 17 January 2010 09:39
		Re: [GMCnet] The pause that makes you heart skip By: Steven Ferguson on Sun, 17 January 2010 09:51
		Re: [GMCnet] The pause that makes you heart skip By: Steven Ferguson on Sun, 17 January 2010 10:02
		[GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Bill Massey on Sun, 17 January 2010 10:12
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Steven Ferguson on Sun, 17 January 2010 10:27
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: GMCWiperMan on Sun, 17 January 2010 15:19
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Byron Songer on Sun, 17 January 2010 17:03
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: GMCWiperMan on Sun, 17 January 2010 17:10
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Rick Denney on Tue, 19 January 2010 16:11
		Re: [GMCnet] Photo Site Editing (was: The pause that makes youheart skip) By: USAussie on Tue, 19 January 2010 16:41
		Re: [GMCnet] Photo Site Editing (was: The pause that makes youheart skip) By: Bill Massey on Tue, 19 January 2010 22:22
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: GMCWiperMan on Tue, 19 January 2010 18:28
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Bill Massey on Tue, 19 January 2010 21:43
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Rick Denney on Wed, 20 January 2010 11:04
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Bill Massey on Wed, 20 January 2010 17:05
		Re: [GMCnet] Photo Site Editing (was: The pause that makesyou heart skip) By: USAussie on Wed, 20 January 2010 17:16
		Re: [GMCnet] Photo Site Editing By: Bill Massey on Wed, 20 January 2010 17:52
		Re: [GMCnet] Photo Site Editing By: Rick Denney on Wed, 20 January 2010 18:41
		Re: [GMCnet] Photo Site Editing (was: The pause that makes you heart skip) By: Bill Massey on Wed, 20 January 2010 18:46
		Re: The pause that makes you heart skip By: Duce Apocalypse on Wed, 13 January 2010 10:52
		vapor lock By: bukzin on Thu, 14 January 2010 23:01
		Re: The pause that makes you heart skip By: RF_Burns on Sat, 16 January 2010 09:20

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