| Issues [message #172988] |
Mon, 11 June 2012 16:09  |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
Karma: 0
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Okay, many of you know that I got my 77 E-II last year and took it to Shawnee, and New Orleans as far as long trips go. About 3 weeks ago, I went to STL and experienced engine roughness which seemed to go away when I turned on the electric fuel pump on. Now, weather did get warmer since the Shawnee trip but please read on.
I did not have cruise control when I bought the rig. The wire from the transducer to the dist was not hooked up. (I THINK it went to the dist but don't come down on me too hard for that. Whichever....it was not hooked up. I hooked it up and determined it was INOP but now I have a new one from Jim K hooked up and working. That was done prior to experiencing the roughness on the STL trip. Coincidence? Can a cruise control affect engine smoothness?
Another question is regarding the fuel pump issue. I have yet to inspect the location of the electric unit. I have yet to replace filters. But, I am assuming a mechanical pump can die and that they are not expensive to just put a new one on. I may try to insulate the fuel lines. I am guessing I may have some vapor lock issues.
Thanks for any ideas that may come forth.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| Re: Issues [message #173048 is a reply to message #172991] |
Tue, 12 June 2012 02:40  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I think you already answered your own question. You turned on the electric fuel pump and the problem went away. You have a fuel delivery issue. Most likely boiling fuel or vapor issues.
One thing to consider is when and where did you last buy fuel. I once saw a chart on the vapor pressure of gasoline sold in Indiana. The vapor pressure was changed every month of the year with July and August being the lowest number. In Indiana all fuel sold in this state in July and August (except for two southern counties)is vapor pressure of 9. Those other counties are be 7. This number is BEFORE the addition of Ethanol. Ethanol raises the vapor pressure number. I think you are fighting the same issues that many other GMCers have and that is fuel vaporization or boiling in warm weather.
To give you a comparison number, the Reid vapor pressure of Aviation gasoline is 5.5 to 7 year round and ethanol mixing is not allowed. We do not want airplanes vapor locking and falling out of the sky.
I think you are in Missouri. Missouri is one the the states that passed an exemption for ethanol. All 91 octane fuel in Missouri is suppose to be ethanol free.
I would start looking at fuel delivery problems.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Issues [message #173054 is a reply to message #173048] |
Tue, 12 June 2012 06:33 |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
Karma: 0
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Senior Member |
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Ken, Missouri exempted ethanol for premium but that only allows the vendors to offer ethanol free premium. However it does not require that they do so. Most around here are getting on the "ethanol free" bandwagon (for premium) and actually advertising that fact on the marquee.
I burn that stuff in my 330 HP Jacobs, btw, six gallons up a ladder at a time.
I also believe it is a vaporization issue but just wanted to see if there was some connection to my repairing the cruise control. I think the answer is to travel in the mornings when it is cool. I did not have that option this past weekend.
thanks to all.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| Re: [GMCnet] Issues [message #173087 is a reply to message #173048] |
Tue, 12 June 2012 11:41 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Ken & All
Here is a chart that showed the summer 2011 vapor pressure requirements.
< http://www.marathonpetroleum.com/brand/Products/RFG_and_RVP_Summer_Regulatory_Requirements/Summer_2011_Reid_Vapor_Pressure_RVP_Regulatory_Requirements /
>
or
http://tinyurl.com/7b4chzd
JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan
On Jun 12, 2012, at 3:42 AM, Ken Burton wrote:
>
>
> I think you already answered your own question. You turned on the
> electric fuel pump and the problem went away. You have a fuel
> delivery issue. Most likely boiling fuel or vapor issues.
>
> One thing to consider is when and where did you last buy fuel. I
> once saw a chart on the vapor pressure of gasoline sold in Indiana.
> The vapor pressure was changed every month of the year with July and
> August being the lowest number. In Indiana all fuel sold in this
> state in July and August (except for two southern counties)is vapor
> pressure of 9. Those other counties are be 7. This number is
> BEFORE the addition of Ethanol. Ethanol raises the vapor pressure
> number. I think you are fighting the same issues that many other
> GMCers have and that is fuel vaporization or boiling in warm weather.
>
> To give you a comparison number, the Reid vapor pressure of Aviation
> gasoline is 5.5 to 7 year round and ethanol mixing is not allowed.
> We do not want airplanes vapor locking and falling out of the sky.
>
> I think you are in Missouri. Missouri is one the the states that
> passed an exemption for ethanol. All 91 octane fuel in Missouri is
> suppose to be ethanol free.
>
> I would start looking at fuel delivery problems.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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