Home » Public Forums » GMCnet » Vapor lock feedback
| Vapor lock feedback [message #318487] |
Sun, 04 June 2017 21:46  |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
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Hello all:
I was looking for some additional feedback on vapor lock, mainly what kind of conditions that you have seen it in. We seem to be troubled by it when temps get up over 83-85 degrees outside, it first started last summer going down the Florida where temps got up to 93+. Since then, we've had an inline fuel pump and rebuilt carb installed by JimB, that seems to have done the trick for getting around the issue (which only seems to happen when slowing down or stopping and trying to get going again).
Also since the inline fuel pump, we've had an aluminum ported Offenhauser intake manifold installed, with the Paterson blockoff kit. We had this done due to cracking of the original manifold. Some thought maybe this would help with vapor lock, however today we again had it happen to us, temps outside were around 83-84 degrees with full sun, we were on the highway for about 45 minutes after taking off cold. After exiting the highway, stopping at a sign, and accelerating again on a backroad, after 10 seconds while accelerating the engine starting surging a little bit. After flipping on the electric aux pump, the surging went away after about 15-20 seconds. We were running the dash AC at the time as well and engine temp seemed normal.
Does this seem to be a little bit extreme with it happening when it's 83-84 degrees out, or is this pretty much what everybody else is experiencing? And is the main fix still just using an aux electric pump back near the tanks? I can't imagine this could be anything else besides vapor lock. Over the years we've had everything in the fuel system either replaced or fixed all the way from the tanks up: fuel tanks cleaned & coated, new rubber hoses, new solenoid, new inline fuel pump and fuel system check (by JimB), new Carter mechanical fuel pump, new fuel filter @ carb, rebuilt carb (from JimB), new aluminum intake with blockoff plates, new Robertshaw 195 thermostat, and even a new fan clutch (Delco 15-4947). Everything seems to be in order.
Feedback, thoughts and anything else is more than welcome. Thanks all!
Chris
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
[Updated on: Sun, 04 June 2017 21:55] Report message to a moderator |
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| Re: Vapor lock feedback [message #318518 is a reply to message #318487] |
Mon, 05 June 2017 11:15  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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My experience with the carburated engine was that you'd falter - or quit completely - at the 1 - 2 shift coming off a light with a long cycle. The engine's been idling, no airflow around the coach, the engine compartment is very hot, and she locks up. At that shift, particularly if your in a turn MAP climbs to ambient and about the only fuel available is from the acceleration pump. Coast to the roadside, wait ten - fifteen minutes, it started up and did well as long as I kept moving. This with decent gas, with alcohol laced gtas it will be worse. The cure was a new fan clutch and a pair of electric pumps in back, taking the mechanical pump out of the system.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Vapor lock feedback [message #318525 is a reply to message #318487] |
Mon, 05 June 2017 13:36 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
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What you are describing is what I have been fighting ever since I got my coach almost nine years ago. One of the things that helps is to have a fresh carburetor fuel filter in place. If that filter gets a little bit clogged, it will disrupt the gas flow enough to cause the vapor lock. I have never had the coach actually stall, but it behaves just as you describe and will do it while climbing a steep grade as well.
I make a habit of turning my electric fuel pump on wherever I anticipate a situation where it might be needed. I usually turn it on when I exit a freeway and know I will be driving on surface streets or when approaching a long uphill climb.
I have also found that using an ethanol treatment, such as Lucas, seems to help a lot. If you can find non-ethanol gas (pure-gas.org), that makes a big difference too. Here in the West, there can be thousands of feet of elevation change encountered in a short distance and the 'winter blend' gas is often sold in areas above 5,000 ft, all year round. Consequently, when you get back down around 2,000 ft or less, the coach doesn't want to run on it.
As Johnny stated, a good fan clutch makes a difference too, as it helps to circulate cooler air into the engine compartment. I don't think it is unusual to have vapor lock issues with ambient temperatures as low as 85 degrees, depending on the gas in your tank. I haven't done this (yet) but it does make sense that eliminating the mechanical fuel pump will eliminate another source of heat for the fuel.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Vapor lock feedback [message #318527 is a reply to message #318487] |
Mon, 05 June 2017 13:49 |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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I was hoping my block off kit would eliminate the vapor lock symptoms. Spring break trip in May was first real run. Full sunny day, mid 80's ambient temps, and a few stop lights in a row it started to stumble if I sat for any length of time. I put an electric pump in the aux line, but have not tested it yet.
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: Vapor lock feedback [message #318532 is a reply to message #318525] |
Mon, 05 June 2017 14:12 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
Karma: 1
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Carl S. wrote on Mon, 05 June 2017 13:36What you are describing is what I have been fighting ever since I got my coach almost nine years ago. One of the things that helps is to have a fresh carburetor fuel filter in place. If that filter gets a little bit clogged, it will disrupt the gas flow enough to cause the vapor lock. I have never had the coach actually stall, but it behaves just as you describe and will do it while climbing a steep grade as well.
I make a habit of turning my electric fuel pump on wherever I anticipate a situation where it might be needed. I usually turn it on when I exit a freeway and know I will be driving on surface streets or when approaching a long uphill climb.
I have also found that using an ethanol treatment, such as Lucas, seems to help a lot. If you can find non-ethanol gas (pure-gas.org), that makes a big difference too. Here in the West, there can be thousands of feet of elevation change encountered in a short distance and the 'winter blend' gas is often sold in areas above 5,000 ft, all year round. Consequently, when you get back down around 2,000 ft or less, the coach doesn't want to run on it.
As Johnny stated, a good fan clutch makes a difference too, as it helps to circulate cooler air into the engine compartment. I don't think it is unusual to have vapor lock issues with ambient temperatures as low as 85 degrees, depending on the gas in your tank. I haven't done this (yet) but it does make sense that eliminating the mechanical fuel pump will eliminate another source of heat for the fuel.
Yes that is spot on to our behavior... climbing a steep grade definitely does it as I think it's because the engine is working overtime and there isn't as much air flow. Not many steep grades here in Michigan to test with, though. 
I was wondering if ethanol treatment does help. Good to know, thanks.
And that's an excellent point on the winter blend, I think we do have some leftover stuff from last fall in the tanks.
Thanks!
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
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| Re: Vapor lock feedback [message #318533 is a reply to message #318527] |
Mon, 05 June 2017 14:14 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
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Tilerpep wrote on Mon, 05 June 2017 13:49I was hoping my block off kit would eliminate the vapor lock symptoms. Spring break trip in May was first real run. Full sunny day, mid 80's ambient temps, and a few stop lights in a row it started to stumble if I sat for any length of time. I put an electric pump in the aux line, but have not tested it yet.
Sounds very similar. If you have your electric pump on a switch, it does take 15-20 seconds to correct the issue, but in our experience it does the trick. Once things are running better, I switch the pump back off and we're good until we stop again.
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
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| Re: [GMCnet] Vapor lock feedback [message #318534 is a reply to message #318527] |
Mon, 05 June 2017 14:16 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
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Tylor, just the Intake Block off will not help a vapor loc issue. It can
help , but we know through working on these coaches, what it takes to
decrease the problem.
Also how one installs pumps , heat shield and others.
On Mon, Jun 5, 2017 at 11:49 AM, Tyler wrote:
> I was hoping my block off kit would eliminate the vapor lock symptoms.
> Spring break trip in May was first real run. Full sunny day, mid 80's
> ambient
> temps, and a few stop lights in a row it started to stumble if I sat for
> any length of time. I put an electric pump in the aux line, but have not
> tested it yet.
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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www.appliedgmc.com
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| Re: [GMCnet] Vapor lock feedback [message #318536 is a reply to message #318534] |
Mon, 05 June 2017 15:00 |
Tony Cook
Messages: 121
Registered: August 2014
Location: Torrance CA
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I second the little Qjet filter only takes a little shmoots that will cause this same issue. It may not be your issue but they are cheap and I keep a few in the glove box and replace from time to time. Even though my fuel system has been redone ie. tanks sealed,fuel lines replaced etc . I too have aux carter and hit it when she starts to stumble seems to help but it has done it to me even with the aux pump on. Has anyone had any luck with the 3 port/return line mechanical pump the Toros had on them to remedy VL ?
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
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| Re: [GMCnet] Vapor lock feedback [message #318541 is a reply to message #318536] |
Mon, 05 June 2017 15:16 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
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Call me and I will tell you where to and how to apply the aux pump.
The mechanical pump with return line can be of help also.
On Mon, Jun 5, 2017 at 1:00 PM, Tony Cook wrote:
> I second the little Qjet filter only takes a little shmoots that will
> cause this same issue. It may not be your issue but they are cheap and I
> keep a
> few in the glove box and replace from time to time. Even though my fuel
> system has been redone ie. tanks sealed,fuel lines replaced etc . I too have
> aux carter and hit it when she starts to stumble seems to help but it has
> done it to me even with the aux pump on. Has anyone had any luck with the 3
> port/return line mechanical pump the Toros had on them to remedy VL ?
> --
> Tony Cook
> 77' Kingsley ' SuperSession 77 '
> Torrance Beach,CA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Vapor lock feedback [message #318545 is a reply to message #318536] |
Mon, 05 June 2017 15:36 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
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Tony Cook wrote on Mon, 05 June 2017 15:00I second the little Qjet filter only takes a little shmoots that will cause this same issue. It may not be your issue but they are cheap and I keep a few in the glove box and replace from time to time. Even though my fuel system has been redone ie. tanks sealed,fuel lines replaced etc . I too have aux carter and hit it when she starts to stumble seems to help but it has done it to me even with the aux pump on. Has anyone had any luck with the 3 port/return line mechanical pump the Toros had on them to remedy VL ?
We ended up also installing an inline metal filter between the metal line and fuel pump inlet to help keep stuff from getting to the pump, just in case. Super easy to change out if needed, and is a little larger than the one at the carb. For what it's worth.
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
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| Re: [GMCnet] Vapor lock feedback [message #318546 is a reply to message #318545] |
Mon, 05 June 2017 15:45 |
Tony Cook
Messages: 121
Registered: August 2014
Location: Torrance CA
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I as well I think 3 filters total one for the aux/elect pump,one at the front cross member and the Qjet . Probably overkill but you would be amazed at what the mechanical fuel pump can hide in it. I replaced mine and found so much crud/particles to fine rust in it . That is what was doing my Qjet filter in often. After new fuel pump changed has been pretty good since.
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
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| Re: Vapor lock feedback [message #318554 is a reply to message #318487] |
Mon, 05 June 2017 21:52 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
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I live in Arizona and, after almost 11 years of summer fuel problems I think I am finally free of them. In addition to the laundry list of the usual stuff mentioned here I installed a FiTech EFI with their Fuel Command Center. The Command center (CC) (and the price) was the thing that convinced me. The CC is a buffer for the bubbles that come from the gas boiling in the tanks and since I installed it I have had no engine vapor issues.
I did continue to have fuel tank issues though - gas boiling in the tanks and venting through the fuel cap, swelling the tanks and making fumes, etc. So a fellow GMCer (Dan Gibb) and I implemented his idea for insulating the tanks. I have a write up and photos at http://minniebiz.com/gmcmotorhome/2017/02/25/insulating-the-fuel-tanks/. We did this in February on both of our coaches and even though it wasn't close to hot until recently I immediately noticed it being easier to fill the tanks - I can't explain that but it has been consistent. On Saturday I drove from the Tucson area to Lake Havasu with temperatures as high as 115 degrees and filled the tanks twice with no issues at all. Never a stumble and no fuel fumes or venting - just like a modern car.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
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| Re: Vapor lock feedback [message #318556 is a reply to message #318487] |
Mon, 05 June 2017 22:49 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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The science behind it is Where in the system the VL is happening. Probably not between the mechanical pump and carb as this is under pressure ( though low) but before the mech pump which are poor "suckers". I have the frame mounted pump with relay signaled from the Aux fuel switch signal to the selector valve. In my case the "fix" is in under 2 seconds ftom the time I flip the switch til the stumble clears. I think the long term road load heat raises the tank temp over time then in dliw traffic the lines loose airflow and VL occurs. Best to flip to Aux when VL is anticipated.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Vapor lock feedback [message #318562 is a reply to message #318557] |
Tue, 06 June 2017 08:02 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
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Harry wrote on Mon, 05 June 2017 23:06Keith V wrote on Mon, 05 June 2017 11:32what coating, mine is steel.
so maybe it did!
________________________________
From: Gmclist on behalf of David H.Jarvis
Sent: Monday, June 5, 2017 11:59:40 AM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Vapor lock feedback
Has anyone had a problem with the ethanol gas dissolving the coating inside the gas tank?
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He said he had the fuel tanks cleaned and COATED. That would not be on the outside.
FYI our tanks were refurbished by Gas Tank Renu, and they coated both the inside and outside. Never had a problem with their work, on another vehicle nor this one so far. But for peace of mind we have a fuel filter just before the pump in case something is sucked through up to that point.
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
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| Re: Vapor lock feedback [message #318565 is a reply to message #318487] |
Tue, 06 June 2017 11:10 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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What I did to elemenate vapor lock in my carbureted engine.block the intake crossover. Coated the fuel tank exterior, heat shields on exhaust pipe, remove mechanics pump and install 2 carter electric outside frame rail, insulate new metal lines from pumps to carburetor running from rear of engine rather then the front. Also no winter gas in hot weather.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Vapor lock feedback [message #318566 is a reply to message #318565] |
Tue, 06 June 2017 11:49 |
Mike Kilroy
Messages: 80
Registered: July 2006
Location: Farmersville, OH (near D...
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Curious, was all that required? Or did the crossover blocking actually
solve it 100%?
On 6/6/2017 12:10 PM, roy keen wrote:
> What I did to elemenate vapor lock in my carbureted engine.block the intake crossover. Coated the fuel tank exterior, heat shields on exhaust pipe,
> remove mechanics pump and install 2 carter electric outside frame rail, insulate new metal lines from pumps to carburetor running from rear of engine
> rather then the front. Also no winter gas in hot weather.
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Mike (AC8V) & Vickie Kilroy
'73 Canyon Land 26' sidebath
455/ceramic filled crossovers
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| Re: [GMCnet] Vapor lock feedback [message #318568 is a reply to message #318566] |
Tue, 06 June 2017 12:11 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Any thoughts about using one of the large Marine fuel/water separator filters back near the gas tanks?
My father used one on his Olds with 350 diesel, to clean up 'filthy' Mexican diesel on the South Texas border. Price was govt controlled $.11 a gallon. (Early 1980's).
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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