Home » Public Forums » GMCnet » [GMCnet] Nasty Hesitation
| [GMCnet] Nasty Hesitation [message #252108] |
Sat, 14 June 2014 13:09  |
Stephen Thomas
Messages: 29
Registered: May 2014
Karma: 0
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I'm having an issue that makes it impossible to get outta town in my coach.
When accelerating, it seems to be fine up to 40 or 50 as long as I'm not
too heavy on the peddle. But when I need to get on the highway or go up any
sort of hill on the highway, the engine starts surging as though it wants
to go but is gasping for air or gas. The more I press on the accelerator,
the more I slow down. Flooring it is out of the question. It will however,
cruise very nicely on level highway with downhill ramps.
The other symptom is a dead spot when I start from a stop. The engine seems
like it will die then surges. It makes stop and go traffic kinda difficult.
I'll spare you all the back story, but you should know that my last
mechanic said I had the wrong jets in the carb and replaced them. I've
taken it back to him and he swears the carb and fuel supply are all good.
I'm not so sure.
Any ideas? Could this be an ignition problem?
Thanks in advance,
Steve
78 Eleganza
Santa Cruz, CA
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| Re: [GMCnet] Nasty Hesitation [message #252110 is a reply to message #252108] |
Sat, 14 June 2014 13:44  |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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Stephen
It sure sounds like it is starving fo fuel
It could be a clogged filter. Remove the filter from the front of the carb and check it. Be sure the filter is in the right direction as shown in the maintenance manual.
It could also be the fuel pump. Are you still using the mechanical fuel pump at the front right side of the engine? Over years the diaphram will stretch and the pressure will go down. You might have to replace it.
Emery Stora
> On Jun 14, 2014, at 12:09 PM, Stephen Thomas wrote:
>
> I'm having an issue that makes it impossible to get outta town in my coach.
>
> When accelerating, it seems to be fine up to 40 or 50 as long as I'm not
> too heavy on the peddle. But when I need to get on the highway or go up any
> sort of hill on the highway, the engine starts surging as though it wants
> to go but is gasping for air or gas. The more I press on the accelerator,
> the more I slow down. Flooring it is out of the question. It will however,
> cruise very nicely on level highway with downhill ramps.
>
> The other symptom is a dead spot when I start from a stop. The engine seems
> like it will die then surges. It makes stop and go traffic kinda difficult.
>
> I'll spare you all the back story, but you should know that my last
> mechanic said I had the wrong jets in the carb and replaced them. I've
> taken it back to him and he swears the carb and fuel supply are all good.
> I'm not so sure.
>
> Any ideas? Could this be an ignition problem?
>
> Thanks in advance,
>
> Steve
> 78 Eleganza
> Santa Cruz, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Nasty Hesitation [message #252118 is a reply to message #252108] |
Sat, 14 June 2014 17:01 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I believe that you need to pull the distributor cap and grab hold of the
rotor with thumb and forefinger and try to turn it slightly counter
clockwise. It should turn a few degrees and then when released, should
spring back to the original position. If it will not turn or spring back ,
your mechanical advance is not working and needs lubrication. Also, use a
vacuum pump and check the vacuum advance cannister on the distributor. Pump
the vacuum pump slowly until you can see the linkage start to move. Observe
the reading. Should be 9" or so and be all in by 18 to 20". If it will not
hold a vacuum, replace it with the correct one for the motorhome. Jwiwd.
Jim Hupy
In Cahokia, Illinois. (E. St. Louis) with the Route 66 Rolling Rally.
On Jun 14, 2014 1:09 PM, "Stephen Thomas" wrote:
> I'm having an issue that makes it impossible to get outta town in my coach.
>
> When accelerating, it seems to be fine up to 40 or 50 as long as I'm not
> too heavy on the peddle. But when I need to get on the highway or go up any
> sort of hill on the highway, the engine starts surging as though it wants
> to go but is gasping for air or gas. The more I press on the accelerator,
> the more I slow down. Flooring it is out of the question. It will however,
> cruise very nicely on level highway with downhill ramps.
>
> The other symptom is a dead spot when I start from a stop. The engine seems
> like it will die then surges. It makes stop and go traffic kinda difficult.
>
> I'll spare you all the back story, but you should know that my last
> mechanic said I had the wrong jets in the carb and replaced them. I've
> taken it back to him and he swears the carb and fuel supply are all good.
> I'm not so sure.
>
> Any ideas? Could this be an ignition problem?
>
> Thanks in advance,
>
> Steve
> 78 Eleganza
> Santa Cruz, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] Nasty Hesitation [message #252126 is a reply to message #252108] |
Sat, 14 June 2014 21:28 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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Stephen Thomas wrote on Sat, 14 June 2014 12:09I'm having an issue that makes it impossible to get outta town in my coach.
When accelerating, it seems to be fine up to 40 or 50 as long as I'm not
too heavy on the peddle. But when I need to get on the highway or go up any
sort of hill on the highway, the engine starts surging as though it wants
to go but is gasping for air or gas. The more I press on the accelerator,
the more I slow down. Flooring it is out of the question. It will however,
cruise very nicely on level highway with downhill ramps.
The other symptom is a dead spot when I start from a stop. The engine seems
like it will die then surges. It makes stop and go traffic kinda difficult.
I'll spare you all the back story, but you should know that my last
mechanic said I had the wrong jets in the carb and replaced them. I've
taken it back to him and he swears the carb and fuel supply are all good.
I'm not so sure.
Any ideas? Could this be an ignition problem?
Thanks in advance,
Steve
78 Eleganza
Santa Cruz, CA
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Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Not enough fuel
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Nasty Hesitation [message #252130 is a reply to message #252128] |
Sat, 14 June 2014 22:23 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
Karma: 0
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Senior Member |
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Quadrajet? Your secondaries may be opening to easily. If your coach has always driven this way I would suspect a bad rebuild. If it just started, could be a failed butterfly valve spring. With the engine thoroughly warmed up, take top off the air cleaner and then rev the engine slowly. The secondary butterfly valve should not move. Then give it quick rev. The butterfly should open slightly and close immediately. If the butterfly opens on the slow rev or flops wide open on the high rev, there's your problem.
FYI if your carb was stock you had the right jets. Did the problem start after your mechanic installed the "right" jets?
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
[Updated on: Sat, 14 June 2014 22:26] Report message to a moderator |
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| Re: [GMCnet] Nasty Hesitation [message #252256 is a reply to message #252108] |
Mon, 16 June 2014 03:04 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Senior Member |
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The jets on a qjet are on the primary side only. Or more accurately, the secondarys are fixed and adjusted with metering rods and hanger size.
Assuming your initial and centrifigal advance are correct its prob the carb. Fuel filter / flow issues usually have a slight delay before manifesting themselves[ ie starts to pull then noses over] as there is fuel in the bowl
As previously mentioned the scondarys could be opening too soon. Make sure the vac line to and the diaphram are intact.
Alternately a couple qjet issues: There is a tab that keets the seconarys from opening when the choke is on on the air horn. If the choke is not fully disengaged or the linkage is wonky it wont open. Also, make sure your accel pump is delivering a full shot. One other is that there are no pumps on the secondary side, but two wells that siphon fuel from the orifices at the front of the seconary flaps at the base of the airhorn. they refill from the main bowl via very small orifices that easily clog if there is trash in the bowl and will cause a stumble.
Q Jets are quirky but are my favorite carb for the street. I used to run an 800 cfm version on a V8 Vega sleeper back in my street racing days and it ran 10.8s
76 Glenbrook
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| Re: [GMCnet] Nasty Hesitation [message #252270 is a reply to message #252108] |
Mon, 16 June 2014 08:13 |
Stephen Thomas
Messages: 29
Registered: May 2014
Karma: 0
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Junior Member |
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ITS FIXED! ...Well, mostly...
After posting the question (and seeing Emery's response), I decided to go
out and start with the simplest things first. So, I replaced the filter on
the carb and a filter near the front tank just like I've done two times
before with no improvement. This time though, I took the electric pump out
of the circuit. I had replaced the mechanical pump a while back but left
this in place as a backup. Turns out that the electric pump has a small
filter on it too...didn't know that. Took it out for a test drive and for
the first time since I've owned it, I felt like I had all my power.
Drove about 140 miles yesterday. Hills and on ramps were no problem.
The "dead spot" when starting from a stop is still there. I'll get into
that another time.
Once again, thanks for all the great help!
Steve
78 Eleganza
Santa Cruz, CA
On Sat, Jun 14, 2014 at 11:09 AM, Stephen Thomas
wrote:
> I'm having an issue that makes it impossible to get outta town in my coach.
>
> When accelerating, it seems to be fine up to 40 or 50 as long as I'm not
> too heavy on the peddle. But when I need to get on the highway or go up any
> sort of hill on the highway, the engine starts surging as though it wants
> to go but is gasping for air or gas. The more I press on the accelerator,
> the more I slow down. Flooring it is out of the question. It will however,
> cruise very nicely on level highway with downhill ramps.
>
> The other symptom is a dead spot when I start from a stop. The engine
> seems like it will die then surges. It makes stop and go traffic kinda
> difficult.
>
> I'll spare you all the back story, but you should know that my last
> mechanic said I had the wrong jets in the carb and replaced them. I've
> taken it back to him and he swears the carb and fuel supply are all good.
> I'm not so sure.
>
> Any ideas? Could this be an ignition problem?
>
> Thanks in advance,
>
> Steve
> 78 Eleganza
> Santa Cruz, CA
>
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| Re: [GMCnet] Nasty Hesitation [message #252277 is a reply to message #252110] |
Mon, 16 June 2014 09:26 |
werewilfs
Messages: 329
Registered: July 2012
Location: Rappahannock County, VA
Karma: 0
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Senior Member |
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That's almost word for word the problem we had with our coach when we first bought it. There was an old electric pump in the line and we would stall out always around 40 mph. Took it out and re-plumbed everything and the coach was going 70 without so much as a hesitation.
Sent from my Windows Phone
________________________________
From: Stephen Thomas
Sent: 6/16/2014 9:13
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Nasty Hesitation
ITS FIXED! ...Well, mostly...
After posting the question (and seeing Emery's response), I decided to go
out and start with the simplest things first. So, I replaced the filter on
the carb and a filter near the front tank just like I've done two times
before with no improvement. This time though, I took the electric pump out
of the circuit. I had replaced the mechanical pump a while back but left
this in place as a backup. Turns out that the electric pump has a small
filter on it too...didn't know that. Took it out for a test drive and for
the first time since I've owned it, I felt like I had all my power.
Drove about 140 miles yesterday. Hills and on ramps were no problem.
The "dead spot" when starting from a stop is still there. I'll get into
that another time.
Once again, thanks for all the great help!
Steve
78 Eleganza
Santa Cruz, CA
On Sat, Jun 14, 2014 at 11:09 AM, Stephen Thomas
wrote:
> I'm having an issue that makes it impossible to get outta town in my coach.
>
> When accelerating, it seems to be fine up to 40 or 50 as long as I'm not
> too heavy on the peddle. But when I need to get on the highway or go up any
> sort of hill on the highway, the engine starts surging as though it wants
> to go but is gasping for air or gas. The more I press on the accelerator,
> the more I slow down. Flooring it is out of the question. It will however,
> cruise very nicely on level highway with downhill ramps.
>
> The other symptom is a dead spot when I start from a stop. The engine
> seems like it will die then surges. It makes stop and go traffic kinda
> difficult.
>
> I'll spare you all the back story, but you should know that my last
> mechanic said I had the wrong jets in the carb and replaced them. I've
> taken it back to him and he swears the carb and fuel supply are all good.
> I'm not so sure.
>
> Any ideas? Could this be an ignition problem?
>
> Thanks in advance,
>
> Steve
> 78 Eleganza
> Santa Cruz, CA
>
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Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Jared & Stefanie Kohl
Rappahannock County, VA
1973 Painted Desert "Onslow"
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