Advice on engine running

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peter bailey

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Mar 17, 2009
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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)
 
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 <

> 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
>
 
Check your distributor mechanical advance.
It can be frozen in full retard.

On Thu, May 2, 2019 at 3:57 PM Peter Bailey via Gmclist <

> 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
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
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.

>
> 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 <

>
>> 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
 
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 <

> 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 <

> >
> > 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 <

> >
> >> 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
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> 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)

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 - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
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.
 
Here’s a video that shows the sticking advance:

http://www.forwardlook.net/images/gmc/IMG_3913.MOV

-Dave
1978 Transmode near Pittsburgh

>
> 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 <

>
>> 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
 
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
http://www.appliedgmc.com
1-800-752-7502
 
My opinion only. Dump in a couple of bottles of SEA FOAM then add new fuel. Dealerships had my 2012 Ford Flex several times and swore all was okay but surging power and pi$$ poor fuel mileage. Two cans of the above stuff made it all good. Won't cost much to try!

Mac in OKC
The Money Pit

Sent from my iPhone

>
> 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
 
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
 
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
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
 
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 <

> 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
> 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
>
 
Dick Paterson has a saying that I have heard him repeat more than once.
"90% of Carburetor problems are Ignition related". Not far off by my
measuring stick. I guess that is why the name of his company is Springfield
Ignition, and not Springfield Carburetor.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Fri, May 3, 2019, 9:08 PM John R. Lebetski via Gmclist <

> 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
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
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
 
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
 
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 <

> 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
http://www.appliedgmc.com
1-800-752-7502
 
That is one of the items I carry in my coach.

> 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 <

>
>> 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
> http://www.appliedgmc.com
> 1-800-752-7502
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
> 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)

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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