Home » Public Forums » GMCnet » Advice on engine running
| Advice on engine running [message #343053] |
Thu, 02 May 2019 17:56  |
peter bailey
Messages: 367
Registered: March 2009
Location: Gawler, South Australia
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Senior Member |
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Hi All, Looking for advice on what might be the problem with the engine not running well.
Our motorhome 1975 Glenwood 455 has not been used for 2 years. It started up okay but idles a little rough and when used on the road is somewhat hesitant on accelaration and strugles to get over 45-50 MPH. I thought it might be due to old fuel but it is still running the same with the tanks full of fresh fuel. I am thinking carby area but I would like advice from the knowledgable on this forum as to where I might need to look for this problem. It was running fine when parked 2 years ago.
Thank you in advance
Peter Bailey
from Ozy (Aussie)
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| Re: [GMCnet] Advice on engine running [message #343056 is a reply to message #343054] |
Thu, 02 May 2019 18:07  |
mjbourgon
Messages: 259
Registered: May 2010
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In the carburetor, the the accelerator pump. The small leather washer could have dried out. When you step on gas pedal the pump is not injecting a jet of gas. That will give you the hesitation you mention
Marcel 1975 glennbrook and palm beach.
> On May 2, 2019, at 5:01 PM, James Hupy via Gmclist wrote:
>
> Look at your distributor. Check the mechanical advance weights and springs.
> If they are sticky, or the rotor will not spring back on their own, Bob's
> your uncle.
> Jim Hupy
>
> On Thu, May 2, 2019, 3:57 PM Peter Bailey via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Hi All, Looking for advice on what might be the problem with the engine
>> not running well.
>> Our motorhome 1975 Glenwood 455 has not been used for 2 years. It started
>> up okay but idles a little rough and when used on the road is somewhat
>> hesitant on accelaration and strugles to get over 45-50 MPH. I thought it
>> might be due to old fuel but it is still running the same with the tanks
>> full of fresh fuel. I am thinking carby area but I would like advice from
>> the knowledgable on this forum as to where I might need to look for this
>> problem. It was running fine when parked 2 years ago.
>> Thank you in advance
>> Peter Bailey
>> from Ozy (Aussie)
>>
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| Re: [GMCnet] Advice on engine running [message #343057 is a reply to message #343056] |
Thu, 02 May 2019 18:39 |
James Hupy
Messages: 6806
Registered: May 2010
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It's not hesitating, It's not making any power. Won't pull above 45 mph.
Jim Hupy
On Thu, May 2, 2019, 4:08 PM Marcel Bourgon via Gmclist <
gmclist@list.gmcnet.org> wrote:
> In the carburetor, the the accelerator pump. The small leather washer
> could have dried out. When you step on gas pedal the pump is not injecting
> a jet of gas. That will give you the hesitation you mention
> Marcel 1975 glennbrook and palm beach.
>
>> On May 2, 2019, at 5:01 PM, James Hupy via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> Look at your distributor. Check the mechanical advance weights and
> springs.
>> If they are sticky, or the rotor will not spring back on their own, Bob's
>> your uncle.
>> Jim Hupy
>>
>> On Thu, May 2, 2019, 3:57 PM Peter Bailey via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> Hi All, Looking for advice on what might be the problem with the engine
>>> not running well.
>>> Our motorhome 1975 Glenwood 455 has not been used for 2 years. It
> started
>>> up okay but idles a little rough and when used on the road is somewhat
>>> hesitant on accelaration and strugles to get over 45-50 MPH. I thought
> it
>>> might be due to old fuel but it is still running the same with the tanks
>>> full of fresh fuel. I am thinking carby area but I would like advice
> from
>>> the knowledgable on this forum as to where I might need to look for this
>>> problem. It was running fine when parked 2 years ago.
>>> Thank you in advance
>>> Peter Bailey
>>> from Ozy (Aussie)
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
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>
>
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| Re: Advice on engine running [message #343059 is a reply to message #343053] |
Thu, 02 May 2019 19:51 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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peter bailey wrote on Thu, 02 May 2019 18:56Hi All, Looking for advice on what might be the problem with the engine not running well.
Our motorhome 1975 Glenwood 455 has not been used for 2 years. It started up okay but idles a little rough and when used on the road is somewhat hesitant on accelaration and strugles to get over 45-50 MPH. I thought it might be due to old fuel but it is still running the same with the tanks full of fresh fuel. I am thinking carby area but I would like advice from the knowledgable on this forum as to where I might need to look for this problem. It was running fine when parked 2 years ago.
Thank you in advance
Peter Bailey
from Ozy (Aussie)
Peter,
I do not disagree with the distributor votes, but I do not know about Aussie motorfuels. Anything that they sell us here can instigate a huge amount of mayhem if given the chance.
If it is not ignition (my first vote actually), then it could be fuel delivery. To this end, first check all the filters. There is at least the one in the carburetor. Be very careful accessing this. I find the best way is to loosen both the connecting line and the filter housing and then remover the four mounting bolts unscrew the line first and then the housing. The housing is a very fine thread and very easily damaged. (If this happens, recovery is expensive if it can happen at all.) Dried and aged out fuel can plug any filter. You may have other filters that have been added over the years.
Another thought would be that there is "varnish" in the bottom of the float bowl. It is possible to open the carburetor in place on the manifold, but it is much less dangerous to pick it off to a bench and open it up. If that is the case, there will be a visible deposit in the bottom of the float bowl. New fuel will usually dissolve this with US motorfuel, but it can take a painful amount of running time to do it.
Please let us know when (if) you find the cause.
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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| Re: Advice on engine running [message #343060 is a reply to message #343059] |
Thu, 02 May 2019 21:17 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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Varnish on the metering rods and jets will cause the fuel delivery to be out of calibration for the throttle position and result in a loss of power while idle and very low speed will seemingly not be affected. BTDT, especially on motorcycles and small equipment engines that sit unused for long periods.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Advice on engine running [message #343061 is a reply to message #343054] |
Thu, 02 May 2019 21:26 |
Dave Stragand
Messages: 307
Registered: October 2017
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Here’s a video that shows the sticking advance:
http://www.forwardlook.net/images/gmc/IMG_3913.MOV
-Dave
1978 Transmode near Pittsburgh
> On May 2, 2019, at 7:01 PM, James Hupy via Gmclist wrote:
>
> Look at your distributor. Check the mechanical advance weights and springs.
> If they are sticky, or the rotor will not spring back on their own, Bob's
> your uncle.
> Jim Hupy
>
> On Thu, May 2, 2019, 3:57 PM Peter Bailey via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Hi All, Looking for advice on what might be the problem with the engine
>> not running well.
>> Our motorhome 1975 Glenwood 455 has not been used for 2 years. It started
>> up okay but idles a little rough and when used on the road is somewhat
>> hesitant on accelaration and strugles to get over 45-50 MPH. I thought it
>> might be due to old fuel but it is still running the same with the tanks
>> full of fresh fuel. I am thinking carby area but I would like advice from
>> the knowledgable on this forum as to where I might need to look for this
>> problem. It was running fine when parked 2 years ago.
>> Thank you in advance
>> Peter Bailey
>> from Ozy (Aussie)
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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1978 Transmode (403)
Pittsburgh, PA
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| Re: [GMCnet] Advice on engine running [message #343062 is a reply to message #343060] |
Thu, 02 May 2019 23:05 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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I feel it is worh the time to look at ALL the above suggestions, as it is
very difficult to pinpoint when people discribe issues.
My tech fought a EFI issue during the week and I was runing out of ideas
and consulted with several that was amilier with that unit.
So when Saturday came by, I figure I have most experiance on EFI and test
drove it.
I must still have a sensative seat and experiance as it felt like a very
low fuel issue with the fuel sloshing around, as I do drive it hard.
I was told that the taks were half full.
Well I figured it would not hurt to dump in around 25 gallons.
Well the issue diapered, .
On Thu, May 2, 2019 at 7:32 PM Terry via Gmclist
wrote:
> Varnish on the metering rods and jets will cause the fuel delivery to be
> out of calibration for the throttle position and result in a loss of power
> while idle and very low speed will seemingly not be affected. BTDT,
> especially on motorcycles and small equipment engines that sit unused for
> long
> periods.
> --
> Terry Kelpien
>
> ASE Master Technician
>
> 73 Glacier 260
>
> Smithfield, Va.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Advice on engine running [message #343067 is a reply to message #343053] |
Fri, 03 May 2019 08:06 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Could be a stuck powervalve in the QJet. Very easy to work on if you know Qjets. Not so much if you do not. Buy the Roe or other Rochester carb books and read up. Noone has mentioned condition of wires, cap rotor and plugs. A visual inpection is no cost. . If you loosen the carb to manifold bolts, only tighten gently or carb crushing damage results
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Advice on engine running [message #343072 is a reply to message #343071] |
Fri, 03 May 2019 09:04 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Sometimes, the "SHOTGUN APPROACH" ( fixing everything possible so that you
increase your chances of hitting the trouble spot) winds up with an irate
customer complaining about overcharging to fix an otherwise low cost
solution. It also doesn't always find the cause of the original complaint.
Based upon Peter's brief description of the problem, and using a lifetime
of diagnostic practice I have acquired over my career, I went with the most
likely cause for the info I had to work with. I easily could be wrong, BUT
if it were me bent over that open hatch, that is a absolutely the first
place I would look.
Jim Hupy
Salem, Or
78 GMC ROYALE 403 with HEI that has done the exact same thing in the past.
On Fri, May 3, 2019, 6:49 AM Marsh Wilkes via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Change fuel filters, carb and inline, probably needs then anyway.
>
> Marsh (rarely post) Wilkes
> Perry Fl
>
> -----Original Message-----
> From: Peter Bailey via Gmclist
> Sent: Thursday, May 02, 2019 6:56 PM
> To: gmclist@list.gmcnet.org
> Cc: Peter Bailey
> Subject: [GMCnet] Advice on engine running
>
> Hi All, Looking for advice on what might be the problem with the engine
> not
> running well.
> Our motorhome 1975 Glenwood 455 has not been used for 2 years. It started
> up
> okay but idles a little rough and when used on the road is somewhat
> hesitant on accelaration and strugles to get over 45-50 MPH. I thought it
> might be due to old fuel but it is still running the same with the tanks
> full of fresh fuel. I am thinking carby area but I would like advice from
> the knowledgable on this forum as to where I might need to look for this
> problem. It was running fine when parked 2 years ago.
> Thank you in advance
> Peter Bailey
> from Ozy (Aussie)
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Advice on engine running [message #343098 is a reply to message #343053] |
Sat, 04 May 2019 08:48 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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That's Dick quoting the great Smokey Yunick That said not knowing the history, could be something like 5/7 are misspatched. In most cases like this a proper visual inspection will find the issue.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Advice on engine running [message #343178 is a reply to message #343053] |
Tue, 07 May 2019 23:40 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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I had my engine hesitate on me on my last trip. Got bad enough that it would only run at idle but not at all as soon as I put it in gear. After nearly having a heart attack, I talked to my mechanic and did carburetor rebuild on the side of the road. It turned out that my final filter (little thing in the carb) was clogged up with varnish. On top of that I found that three of the metering tubes were disconnected and were sitting in the bottom of carburetor. After putting I got them put back where they actually belong, I was surprised by how much power the engine has now.
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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| Re: [GMCnet] Advice on engine running [message #343191 is a reply to message #343178] |
Wed, 08 May 2019 08:48 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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We replace tons of that small filter at our shop as people do not realize
that the new fuel is washing the old crud loose from the tanks and plugging
up the small filter
On Wed, May 8, 2019 at 12:33 AM Vadim Jitkov via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I had my engine hesitate on me on my last trip. Got bad enough that it
> would only run at idle but not at all as soon as I put it in gear. After
> nearly having a heart attack, I talked to my mechanic and did carburetor
> rebuild on the side of the road. It turned out that my final filter (little
> thing in the carb) was clogged up with varnish. On top of that I found
> that three of the metering tubes were disconnected and were sitting in the
> bottom of carburetor. After putting I got them put back where they
> actually belong, I was surprised by how much power the engine has now.
> --
> Vadim Jitkov
> '76 Glenbrook 26'
> Pullman, WA
>
> _______________________________________________
> 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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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Advice on engine running [message #343192 is a reply to message #343191] |
Wed, 08 May 2019 08:49 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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That is one of the items I carry in my coach.
On Wed, May 8, 2019 at 6:48 AM Jim Kanomata wrote:
> We replace tons of that small filter at our shop as people do not realize
> that the new fuel is washing the old crud loose from the tanks and plugging
> up the small filter
>
> On Wed, May 8, 2019 at 12:33 AM Vadim Jitkov via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> I had my engine hesitate on me on my last trip. Got bad enough that it
>> would only run at idle but not at all as soon as I put it in gear. After
>> nearly having a heart attack, I talked to my mechanic and did carburetor
>> rebuild on the side of the road. It turned out that my final filter (little
>> thing in the carb) was clogged up with varnish. On top of that I found
>> that three of the metering tubes were disconnected and were sitting in the
>> bottom of carburetor. After putting I got them put back where they
>> actually belong, I was surprised by how much power the engine has now.
>> --
>> Vadim Jitkov
>> '76 Glenbrook 26'
>> Pullman, WA
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Advice on engine running [message #343199 is a reply to message #343053] |
Wed, 08 May 2019 11:01 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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peter bailey wrote on Thu, 02 May 2019 17:56Hi All, Looking for advice on what might be the problem with the engine not running well.
Our motorhome 1975 Glenwood 455 has not been used for 2 years. It started up okay but idles a little rough and when used on the road is somewhat hesitant on accelaration and strugles to get over 45-50 MPH. I thought it might be due to old fuel but it is still running the same with the tanks full of fresh fuel. I am thinking carby area but I would like advice from the knowledgable on this forum as to where I might need to look for this problem. It was running fine when parked 2 years ago.
Thank you in advance
Peter Bailey
from Ozy (Aussie)
Since you description says it ran fine 2 years ago and then sat idle since then.
Two things could have happened.
1. Something rusted, like the distributor advance.
2. Gasoline evaporated and left a gummy varnish like goo. I would replace the carb filter because it is easy and cheap. Then I would suspect varnish collection in the carb. I restarted one a year ago the sat for 18 years. At Dick Paterson's suggestion I filled the carb with straight carb cleaner and let it soak for a day. Then I cranked and cranked until the carb cleaner (in the carb) was replaced with gasoline and the engine started. It ran beautifully and has never has a fuel delivery problem since.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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