Home » Public Forums » GMCnet » What the?
| What the? [message #66664] |
Fri, 04 December 2009 21:33  |
Mitch
Messages: 272
Registered: May 2009
Location: Tacoma, Wa
Karma: 0
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OK, I'm willing to cop to not having had much to do with non-computerized engines over the last 20 years so it's possible that I'm just not groking today's problem properly, so here goes:
Had The Beast out for a bit of exercise today.
Dropped ten gallons of gas in the tank (gave me half a tank by the gauge) and hit the freeway north bound. I was running up to the local rest stop to dump the waste tank, so It was about 5-6 miles of freeway, with the last bit uphill from Fife.
Dumped the tank, visited the rest rooms and got back on the freeway. All the time in the rest stop the engine had been idling.
As we were coming up to speed, the engine started to stumble, then died. I coasted to the shoulder, tried the key, and the engine fired off right away.
Went up to the next off ramp, circled around and back on the freeway south bound. Now we are going slightly down hill, every thing is fine. Down thru Fife, flat, then up the slight grade past the Tacoma Dome. Soon she starts to stumble again. I'm just keeping a light throttle, as I'm approaching my exit, but there is still some stumbling. Onto Hwy 16 and on around it is all fairly flat, no problems all the way home.
Here is what I know; I had about half a tank of gas, while some of it was a few months old, ten gallons was fresh.
This only happened on a slight up grade, probably less than 2%.
(I don't even want to know what would happen on greater)
The fact it started instantly after dieing (I think) eliminates a blocked filter or pickup.
I could think a vapor lock after idling at the rest stop, but we were only in the 40s today, and that doesn't explain the repeat.
I'm open to suggestions.
Oh, and just to add to the fun, the Wife is sitting in the other seat.
Mitch
Tacoma, Wa.
'80 Spitfire
'03 Windstar
'77 Jaguar XJ6-C
X(very)'76 PB 26 "The Beast"
Where it rains, always.
It's wet, No sun, Gray.
Go to Oregon.
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| Re: What the? [message #66666 is a reply to message #66664] |
Fri, 04 December 2009 21:43  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Change the fuel filter.
After that you are looking at vapor lock. I doubt that is a vapor lock problem in these temps but they do change the vapor pressure in winter mix gas to allow for easier starting.
I'd go with replacing the filter. Are you buying ethanol mixed gas? If so, the ethanol can loosen up crap in your fuel system and send it to the filter if your vehicle is not use to using ethanol mixed fuel.
If the the filter fixes it, buy a spare and keep it in the coach.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: What the? [message #66668 is a reply to message #66666] |
Fri, 04 December 2009 21:45 |
Mitch
Messages: 272
Registered: May 2009
Location: Tacoma, Wa
Karma: 0
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Senior Member |
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| Ken Burton wrote on Fri, 04 December 2009 19:43 |
Change the fuel filter.
After that you are looking at vapor lock. I doubt that is a vapor lock problem in these temps but they do change the vapor pressure in winter mix gas to allow for easier starting.
I'd go with replacing the filter. Are you buying ethanol mixed gas? If so, the ethanol can loosen up crap in your fuel system and send it to the filter if your vehicle is not use to using ethanol mixed fuel.
If the the filter fixes it, buy a spare and keep it in the coach.
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Always go with the easiest fix first.
After that Easter Egg it.
Mitch
Tacoma, Wa.
'80 Spitfire
'03 Windstar
'77 Jaguar XJ6-C
X(very)'76 PB 26 "The Beast"
Where it rains, always.
It's wet, No sun, Gray.
Go to Oregon.
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| Re: [GMCnet] What the? [message #66669 is a reply to message #66664] |
Fri, 04 December 2009 21:45 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Mitch,
Did you miss Jim Bounds' posts earlier today describing your problem almost
exactly? He's had a rash of customers lately with clogged fuel filters,
probably caused by ethanol loosening old deposits. Your symptoms are all to
familiar.
It's not at all unusual for the engine to immediately restart, and even run
nicely without load when a filter is almost blocked -- the residual flow is
enough to sustain light loads.
JMHO,
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
On Fri, Dec 4, 2009 at 10:33 PM, Mitch <Yowzax3@harbornet.com> wrote:
> ...As we were coming up to speed, the engine started to stumble, then died.
> I coasted to the shoulder, tried the key, and the engine fired off right
> away.
> Went up to the next off ramp, circled around and back on the freeway south
> bound. Now we are going slightly down hill, every thing is fine. Down thru
> Fife, flat, then up the slight grade past the Tacoma Dome. Soon she starts
> to stumble again. I'm just keeping a light throttle, as I'm approaching my
> exit, but there is still some stumbling. Onto Hwy 16 and on around it is all
> fairly flat, no problems all the way home...
> Here is what I know; I had about half a tank of gas, while some of it was a
> few months old, ten gallons was fresh.
> This only happened on a slight up grade, probably less than 2%.
> (I don't even want to know what would happen on greater)
> The fact it started instantly after dieing (I think) eliminates a blocked
> filter or pickup.
> I could think a vapor lock after idling at the rest stop, but we were only
> in the 40s today, and that doesn't explain the repeat.
> I'm open to suggestions.
> Oh, and just to add to the fun, the Wife is sitting in the other seat.
> --
> Mitch
> Tacoma, Wa.
> '80 Spitfire
> '03 Windstar
> X(very)PB 26 "The Beast"
> Where it rains, always.
>
> It's wet, No sun, Gray.
> Go to Oregon.
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: What the? [message #66670 is a reply to message #66666] |
Fri, 04 December 2009 21:55 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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| Ken Burton wrote on Fri, 04 December 2009 22:43 |
Change the fuel filter.
After that you are looking at vapor lock. I doubt that is a vapor lock problem in these temps but they do change the vapor pressure in winter mix gas to allow for easier starting.
I'd go with replacing the filter. Are you buying ethanol mixed gas? If so, the ethanol can loosen up crap in your fuel system and send it to the filter if your vehicle is not use to using ethanol mixed fuel.
If the the filter fixes it, buy a spare and keep it in the coach.
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I would do the filter also as Ken B suggests. Ken probably knows more about it as he is a pilot, but maybe wind chill under the coach and moisture icing in the line or filter causing a restriction when asking for more fuel under load???
C. Boyd
76 Crestmont
East Tennessee
[Updated on: Fri, 04 December 2009 21:55] Report message to a moderator |
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| Re: What the? [message #66671 is a reply to message #66670] |
Fri, 04 December 2009 21:57 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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| C Boyd wrote on Fri, 04 December 2009 22:55 |
| Ken Burton wrote on Fri, 04 December 2009 22:43 |
Change the fuel filter.
After that you are looking at vapor lock. I doubt that is a vapor lock problem in these temps but they do change the vapor pressure in winter mix gas to allow for easier starting.
I'd go with replacing the filter. Are you buying ethanol mixed gas? If so, the ethanol can loosen up crap in your fuel system and send it to the filter if your vehicle is not use to using ethanol mixed fuel.
If the the filter fixes it, buy a spare and keep it in the coach.
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I would do the filter also as Ken B suggests. Ken probably knows more about it as he is a pilot, but maybe wind chill under the coach and moisture icing in the line or filter causing a restriction when asking for more fuel under load???
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OOOPS.....Sorry, I was thinking of Mr Ken Burton. But Ken H is a pilot also...
C. Boyd
76 Crestmont
East Tennessee
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| Re: What the? [message #66678 is a reply to message #66664] |
Fri, 04 December 2009 23:04 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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| Mitch wrote on Fri, 04 December 2009 19:33 |
OK, I'm willing to cop to not having had much to do with non-computerized engines over the last 20 years so it's possible that I'm just not groking today's problem properly, so here goes:
Had The Beast out for a bit of exercise today.
Dropped ten gallons of gas in the tank (gave me half a tank by the gauge) and hit the freeway north bound. I was running up to the local rest stop to dump the waste tank, so It was about 5-6 miles of freeway, with the last bit uphill from Fife.
Dumped the tank, visited the rest rooms and got back on the freeway. All the time in the rest stop the engine had been idling.
As we were coming up to speed, the engine started to stumble, then died. I coasted to the shoulder, tried the key, and the engine fired off right away.
Went up to the next off ramp, circled around and back on the freeway south bound. Now we are going slightly down hill, every thing is fine. Down thru Fife, flat, then up the slight grade past the Tacoma Dome. Soon she starts to stumble again. I'm just keeping a light throttle, as I'm approaching my exit, but there is still some stumbling. Onto Hwy 16 and on around it is all fairly flat, no problems all the way home.
Here is what I know; I had about half a tank of gas, while some of it was a few months old, ten gallons was fresh.
This only happened on a slight up grade, probably less than 2%.
(I don't even want to know what would happen on greater)
The fact it started instantly after dieing (I think) eliminates a blocked filter or pickup.
I could think a vapor lock after idling at the rest stop, but we were only in the 40s today, and that doesn't explain the repeat.
I'm open to suggestions.
Oh, and just to add to the fun, the Wife is sitting in the other seat.
|
Mitch: since you have my old coach, did you have the electric fuel pump on?
The center position on the switch is off, up is prime (as I recall) and down is on while the alternator is running. That is a safety so if the engine stops, so does the electric fuel pump. The switch should NOT be left in the up position, after the engine is started.
Also, have you changed the spin on fuel filter under the coach near the pump? It is the one I put on about 3 years ago, when I did that job. Since the coach has sat more than it has been driven, I would not be surprised if the fuel filter needs replacement. Also, the filter at the carb is still in place. I would change it out also. Be careful of the threads into the carb.
Rob Allen
former owner of '76 x-PB
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| Re: What the? [message #66680 is a reply to message #66678] |
Fri, 04 December 2009 23:24 |
Mitch
Messages: 272
Registered: May 2009
Location: Tacoma, Wa
Karma: 0
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Senior Member |
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| idrob wrote on Fri, 04 December 2009 21:04 |
| Mitch wrote on Fri, 04 December 2009 19:33 |
OK, I'm willing to cop to not having had much to do with non-computerized engines over the last 20 years so it's possible that I'm just not groking today's problem properly, so here goes:
Had The Beast out for a bit of exercise today.
Dropped ten gallons of gas in the tank (gave me half a tank by the gauge) and hit the freeway north bound. I was running up to the local rest stop to dump the waste tank, so It was about 5-6 miles of freeway, with the last bit uphill from Fife.
Dumped the tank, visited the rest rooms and got back on the freeway. All the time in the rest stop the engine had been idling.
As we were coming up to speed, the engine started to stumble, then died. I coasted to the shoulder, tried the key, and the engine fired off right away.
Went up to the next off ramp, circled around and back on the freeway south bound. Now we are going slightly down hill, every thing is fine. Down thru Fife, flat, then up the slight grade past the Tacoma Dome. Soon she starts to stumble again. I'm just keeping a light throttle, as I'm approaching my exit, but there is still some stumbling. Onto Hwy 16 and on around it is all fairly flat, no problems all the way home.
Here is what I know; I had about half a tank of gas, while some of it was a few months old, ten gallons was fresh.
This only happened on a slight up grade, probably less than 2%.
(I don't even want to know what would happen on greater)
The fact it started instantly after dieing (I think) eliminates a blocked filter or pickup.
I could think a vapor lock after idling at the rest stop, but we were only in the 40s today, and that doesn't explain the repeat.
I'm open to suggestions.
Oh, and just to add to the fun, the Wife is sitting in the other seat.
|
Mitch: since you have my old coach, did you have the electric fuel pump on?
The center position on the switch is off, up is prime (as I recall) and down is on while the alternator is running. That is a safety so if the engine stops, so does the electric fuel pump. The switch should NOT be left in the up position, after the engine is started.
Also, have you changed the spin on fuel filter under the coach near the pump? It is the one I put on about 3 years ago, when I did that job. Since the coach has sat more than it has been driven, I would not be surprised if the fuel filter needs replacement. Also, the filter at the carb is still in place. I would change it out also. Be careful of the threads into the carb.
|
I was going to write and ask you about that. So I'll jump on it tomorrow.
Fuel switch was in the center (normal position).
By the way, how is the warm?
Missed the other postings on fuel filters, I'll jump back and scan them.
Mitch
Tacoma, Wa.
'80 Spitfire
'03 Windstar
'77 Jaguar XJ6-C
X(very)'76 PB 26 "The Beast"
Where it rains, always.
It's wet, No sun, Gray.
Go to Oregon.
[Updated on: Fri, 04 December 2009 23:25] Report message to a moderator |
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| Re: What the? [message #66683 is a reply to message #66671] |
Fri, 04 December 2009 23:38 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| C Boyd wrote on Fri, 04 December 2009 21:57 |
| C Boyd wrote on Fri, 04 December 2009 22:55 |
| Ken Burton wrote on Fri, 04 December 2009 22:43 |
Change the fuel filter.
After that you are looking at vapor lock. I doubt that is a vapor lock problem in these temps but they do change the vapor pressure in winter mix gas to allow for easier starting.
I'd go with replacing the filter. Are you buying ethanol mixed gas? If so, the ethanol can loosen up crap in your fuel system and send it to the filter if your vehicle is not use to using ethanol mixed fuel.
If the the filter fixes it, buy a spare and keep it in the coach.
|
I would do the filter also as Ken B suggests. Ken probably knows more about it as he is a pilot, but maybe wind chill under the coach and moisture icing in the line or filter causing a restriction when asking for more fuel under load???
|
OOOPS.....Sorry, I was thinking of Mr Ken Burton. But Ken H is a pilot also...
|
Yea, but Ken H. flew an oil burner large enough to put his GMC inside. I do not know if that counts as a real airplane.
I'm just jealous that I never even got to ride in one of those, let alone fly one.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: What the? [message #66689 is a reply to message #66680] |
Sat, 05 December 2009 00:40 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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[quote title=Mitch wrote on Fri, 04 December 2009 21:24]| idrob wrote on Fri, 04 December 2009 21:04 |
| Mitch wrote on Fri, 04 December 2009 19:33 |
Mitch: since you have my old coach, did you have the electric fuel pump on?
The center position on the switch is off, up is prime (as I recall) and down is on while the alternator is running. That is a safety so if the engine stops, so does the electric fuel pump. The switch should NOT be left in the up position, after the engine is started.
Also, have you changed the spin on fuel filter under the coach near the pump? It is the one I put on about 3 years ago, when I did that job. Since the coach has sat more than it has been driven, I would not be surprised if the fuel filter needs replacement. Also, the filter at the carb is still in place. I would change it out also. Be careful of the threads into the carb.
|
I was going to write and ask you about that. So I'll jump on it tomorrow.
Fuel switch was in the center (normal position).
By the way, how is the warm?
Missed the other postings on fuel filters, I'll jump back and scan them.
|
Mitch, the center position on the switch is OFF, so that means the mechanical fuel pump does all the work. I am almost positive that if you had turned it on (down) the electric fuel pump would have been working and you would have been fine. My best guess is that the main fuel filter (spin on one, near the pump, under the coach, forward of the tanks) needs replacing or the original mechanical fuel pump has become tired and cannot pull the fuel through the filter and the electric fuel pump.
There is no real reason not to use the electric fuel pump all the time, if you want; That is leave the switch in the down position. You can prime the carb if the rig has been siting for a while by having the key on, and the switch in the UP position, but remember to put it back down when the engine starts so you don't bypass the safety system. I wanted a center off, spring loaded on "up" and stay on "down" switch, but could not find one when I built that system.
We had a lot to go over when you picked the coach up from me, and I am not surprised you may have missed how that switch works and what it is for.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] What the? [message #66697 is a reply to message #66664] |
Sat, 05 December 2009 06:20 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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It sounds like you problem is present during heavy throttle, not
partial throttle. I don't know what year your coach is but my'76 had
the same problem every time I got into the secondaries. Here is what
caused my problem:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=17726
It wasn't the lack of fuel, it was too much since this little choke
actuated "shoe" was occasionally preventing the rear secondary air
valves from opening causing a seriously rich condition. Same result.
I would pull over and the coach would instantly start up. '77 and '78
saw the removal of this shoe on all QJets. Simple to remove.
On Fri, Dec 4, 2009 at 8:33 PM, Mitch <Yowzax3@harbornet.com> wrote:
As we were coming up to speed, the engine started to stumble, then
died. I coasted to the shoulder, tried the key, and the engine fired
off right away.
> Went up to the next off ramp, circled around and back on the freeway south bound. Now we are going slightly down hill, every thing is fine. Down thru Fife, flat, then up the slight grade past the Tacoma Dome. Soon she starts to stumble again. I'm just keeping a light throttle, as I'm approaching my exit, but there is still some stumbling. Onto Hwy 16 and on around it is all fairly flat, no problems all the way home.
> Here is what I know; I had about half a tank of gas, while some of it was a few months old, ten gallons was fresh.
> This only happened on a slight up grade, probably less than 2%.
> (I don't even want to know what would happen on greater)
> The fact it started instantly after dieing (I think) eliminates a blocked filter or pickup.
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] What the? [message #66701 is a reply to message #66685] |
Sat, 05 December 2009 06:54 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Yeah, but Ken B. still does it. It's been so long since I did that I can
only claim to "have been".
Thing is, one can never completely purge all those numbers from one's mind.
Max continuous TIT=932*F, MIL=961*F-977*F, cargo compartment 41'x9'x10',
etc. :-)
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
On Sat, Dec 5, 2009 at 12:51 AM, Dan Gregg <gregg_dan@hotmail.com> wrote:
>
>
>
>
>
> Yea, but Ken H. flew an oil burner large enough to put his GMC inside. I
> do not know if that counts as a real airplane.
>
> I'm just jealous that I never even got to ride in one of those, let alone
> fly one.
>
> Ken B.
>
>
> [/quote]
>
> I never got to fly in one either but did help several pilots land them from
> the rapcon.
> Dan
> --
>
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| Re: [GMCnet] What the? [message #66707 is a reply to message #66701] |
Sat, 05 December 2009 07:59 |
rwbmitiopt@comcast.net
Messages: 189
Registered: April 2005
Karma: 0
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Senior Member |
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In describing the power supply to the electric fuel pump Rob Allen described his ideal switch
"I wanted a center off, spring loaded on "up" and stay on "down" switch, but could not find one when I built that system."
Anyone know if such a switch is available? I would like to wire my pump this way.
TIA,
Randy
Randall Burns
Sammamish WA
75 EX GB
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| Re: [GMCnet] What the? [message #66724 is a reply to message #66697] |
Sat, 05 December 2009 20:26 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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| Steven Ferguson wrote on Sat, 05 December 2009 04:20 |
It sounds like you problem is present during heavy throttle, not
partial throttle. I don't know what year your coach is but my'76 had
the same problem every time I got into the secondaries. Here is what
caused my problem:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=17726
It wasn't the lack of fuel, it was too much since this little choke
actuated "shoe" was occasionally preventing the rear secondary air
valves from opening causing a seriously rich condition. Same result.
I would pull over and the coach would instantly start up. '77 and '78
saw the removal of this shoe on all QJets. Simple to remove.
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
|
Steve: I had that problem on Mitch's coach when I owned it. Here is my album about what I found and how I fixed it, for anyone else who is interested. I did leave it in place, rather than removing it. Maybe removal would be the best thing.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4420
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] What the? [message #66726 is a reply to message #66708] |
Sat, 05 December 2009 20:31 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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| Larry wrote on Sat, 05 December 2009 14:14 |
| rwbmitiopt wrote on Sat, 05 December 2009 07:59 |
In describing the power supply to the electric fuel pump Rob Allen described his ideal switch
"I wanted a center off, spring loaded on "up" and stay on "down" switch, but could not find one when I built that system."
Anyone know if such a switch is available? I would like to wire my pump this way.
TIA,
Randy
|
Randy,
Maybe try doing this:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=3999
Power comes from the alternator isolator connection so that pump only runs when key is in start, or run with engine running. A bypass button switch allows priming when coach has set for long period of time. Works for me...JWID
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Randy: Email has been going back and forth privately on this switch. Bob Burkitt suggested this (quote from his email)
"Rob Allen mentions a better switch option for the electric fuel pump, it should have a momentary option for priming as a "constant on" position for priming would cause fuel to be under constant pressure and pose a hazard in the event of a leak or a fire. I used a DPDT Cutler-Hammer heavy-duty metal toggle switch with the center position as "off', one direction as "constant on" and the opposite direction as "momentary on". The "momentary on" is for priming and bypasses the recommended (required?) Low Oil Pressure (LOP) switch in the power supply. When the toggle is released the pump shuts off and cannot be left on in error. The switch that I used is CH 55081 and at the time was less than $10 in 2002"
Bob is always an excellent source of information.
Rob Allen
former owner of '76 x-PB
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