Loss of Power - Need your thoughts

S

steve adams

Member
Sep 6, 2013
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I am posting a further update on this in hopes it may help someone who might experience the same issue. I have continued to have issues with no power
coming off of idle. I had replaced both the fuel pump and the distributor but continued to have issues. Engine starts fine including the choke
operation and fast idle setting. Everything normal until you put it in gear and try to move off idle and the engine would stumble with no power. Top
speed was 15 to 20 mph and I was afraid I would not make it home if I took it out to test drive. On test drive I discovered that if I put the pedal
to the floor it would accelerate to 65 mph but could not cruise or maintain any speed. Only accelerate at wide open throttle. My driveway has a
slight incline and sure enough I could not make it up the driveway. In desperation I put the pedal to the floor, it stumbled and then came alive and
I did a burn out half way up the driveway. With idle good and appearent power from the secondaries I now assumed it had to be carb primary circuit
related.

I called Ken Frey to see if he could look at it. Although he was trying to wrap up and get out of town for the holidays, he said to take the carb off
and bring it over. I got a good education on Q-jet. We disassembled, inspected, cleaned, and reassembled. Nothing was drastically wrong but it was
dirty and gunked up inside. Carb was fully rebuilt by Ken in fall of 2014. I have two filters, one in the carb and one before the pump. I also keep
tanks full, treat with stabill, and run every 30 days.

Anyway, I installed the carb with a new base gasket and torqued the 4 mounting bolts to 10 lbs. After making all connections it started fine and I
went out for a test drive. I had good power across all RPM ranges including climbing some pretty good local hills.

I hope this carb cleaning is the final fix on my loss of power issues. I suspect ethanol gas may have something to do with it.

Many thanks Ken and to all who provided ideas and assistance. I am back on the road again.
--
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
 
> I am posting a further update on this in hopes it may help someone who might experience the same issue. I have continued to have issues with no
> power coming off of idle. I had replaced both the fuel pump and the distributor but continued to have issues. Engine starts fine including the
> choke operation and fast idle setting. Everything normal until you put it in gear and try to move off idle and the engine would stumble with no
> power. Top speed was 15 to 20 mph and I was afraid I would not make it home if I took it out to test drive. On test drive I discovered that if I
> put the pedal to the floor it would accelerate to 65 mph but could not cruise or maintain any speed. Only accelerate at wide open throttle. My
> driveway has a slight incline and sure enough I could not make it up the driveway. In desperation I put the pedal to the floor, it stumbled and
> then came alive and I did a burn out half way up the driveway. With idle good and appearent power from the secondaries I now assumed it had to be
> carb primary circuit related.
>
> I called Ken Frey to see if he could look at it. Although he was trying to wrap up and get out of town for the holidays, he said to take the carb
> off and bring it over. I got a good education on Q-jet. We disassembled, inspected, cleaned, and reassembled. Nothing was drastically wrong but
> it was dirty and gunked up inside. Carb was fully rebuilt by Ken in fall of 2014. I have two filters, one in the carb and one before the pump. I
> also keep tanks full, treat with stabill, and run every 30 days.
>
> Anyway, I installed the carb with a new base gasket and torqued the 4 mounting bolts to 10 lbs. After making all connections it started fine and I
> went out for a test drive. I had good power across all RPM ranges including climbing some pretty good local hills.
>
> I hope this carb cleaning is the final fix on my loss of power issues. I suspect ethanol gas may have something to do with it.
>
> Many thanks Ken and to all who provided ideas and assistance. I am back on the road again.

Steve,

Glad to hear that the problem is handled. I missed this thread because I was at Mansfield and did not follow the forum closely during that.

I can almost guarantee that the problem was some restriction of the primary power circuit. Of course, Ken did the right thing. I have had these same
"mystery fixes", but it was only with the third of the same unit that disassembling the carburetor over clean white paper found the debris. If you do
the normal knock down and blow out, it is easy tp fix it without ever finding the actual problem. Yes, this can be "engine temperature" dependent
because the flow problem can get changed by the carburetor temperature.

Matt

--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
Your fuel filter must be plugged, blame yourself for not changing it
frequently.

> Yeah! Thanks for finishing the thread. Disheartening that a carb overhaul
> only lasted less than 3 years.
>
> bdub
>
>

>
> I am posting a further update on this in hopes it may be ... Snip ...
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
Also check all the vac lines and snug the 4 carb mounting bolts.
This is not a car/pickup, and there is lot of load on the engine that most
of you do not realize.
Therefor you need to learn these things .
Fuel consumption is twice that of a car/pick up, so the fuel filter will
load up with particulates.
Also keep in mind, the new ethanol fuel is washing your old gummed up tank
and that mini fuel filter is loading up.

> Your fuel filter must be plugged, blame yourself for not changing it
> frequently.
>
> On Wed, Dec 28, 2016 at 12:43 PM, Billy Massey

>
>> Yeah! Thanks for finishing the thread. Disheartening that a carb
>> overhaul
>> only lasted less than 3 years.
>>
>> bdub
>>
>>

>>
>> I am posting a further update on this in hopes it may be ... Snip ...
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Fremont,CA
> jimk
> http://www.appliedgmc.com
> 1-800-752-7502
>

--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
Since I only monitor Gmail, I did not see the complaint, maybe one of you
can relay it so I can read it first hand.

> Also check all the vac lines and snug the 4 carb mounting bolts.
> This is not a car/pickup, and there is lot of load on the engine that most
> of you do not realize.
> Therefor you need to learn these things .
> Fuel consumption is twice that of a car/pick up, so the fuel filter will
> load up with particulates.
> Also keep in mind, the new ethanol fuel is washing your old gummed up tank
> and that mini fuel filter is loading up.
>
> On Wed, Dec 28, 2016 at 2:01 PM, Jim Kanomata

>
>> Your fuel filter must be plugged, blame yourself for not changing it
>> frequently.
>>
>> On Wed, Dec 28, 2016 at 12:43 PM, Billy Massey

>>
>>> Yeah! Thanks for finishing the thread. Disheartening that a carb
>>> overhaul
>>> only lasted less than 3 years.
>>>
>>> bdub
>>>
>>>

>>>
>>> I am posting a further update on this in hopes it may be ... Snip ...
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>>
>>
>>
>> --
>> Jim Kanomata
>> Applied/GMC, Fremont,CA
>> jimk
>> http://www.appliedgmc.com
>> 1-800-752-7502
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Fremont,CA
> jimk
> http://www.appliedgmc.com
> 1-800-752-7502
>

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

Thanks for the advice on the fuel filters. I failed to mention that we also replaced the fuel filter in the carb inlet housing. It was the correct
filter with the check valve/ball. We opened up the old one and it was dirty but not plugged, nor was it water logged or water damaged. One
interesting thing about my carb is that it has a metal tag installed over the fuel inlet that says "No Filter inside Carb, Check filter near fuel
pump". Someone along the line had put that tag there to steer others away from the fuel inlet filter. I had not opened the inlet up, but have
changed the in-line filter before the fuel pump each year. I'm glad the filter was there because it caught a bunch of junk the in-line filter missed.
I'm thinking I should ditch the cheap Autozone in-line filter for a WIX or other higher quality unit. I watched a lot of you tube videos on Q'jets.
I have a much better understanding of them now. Simple float and needle valve, idle circuit, enrichment circuit, primary circuit, and secondary
circuit. I am just happy they are all working and transitioning nicely.

Ok, what's next on my list?
--
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
 
One of the things that Ken Frey likely did is free up the power piston in the Q jet. That power piston is physically connected to metering rods and
controlled by manifold vacuum. As the piston is lifted by spring pressure against lesser manifold vacuum, the metering rods lift in the high speed
jets allowing for a richer mixture and increased power. Over the years of operation the operation of that piston can be compromised by carbon and/or
varnish buildup and can become stuck in the full down position which does not allow for more fuel when needed for acceleration. Symptoms of this
condition are exhibited by bogging and backfire because of a lean condition. Often you can "unstick" that piston temporarily by lifting the power
piston with a needle nose pliers and working it a little. Then take it apart when you have time and clean it with carb cleaner. JWIT
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
Whoa! Valve / Ball in the carb filter? What's this?

bdub

-----Original Message-----
From: Gmclist On Behalf Of Steve Adams
Sent: Wednesday, December 28, 2016 4:37 PM

... snip ...
I failed to mention that we also replaced the fuel filter in the carb inlet
housing. It was the correct filter with the check valve/ball. We opened up the
old one and it was dirty but not plugged, nor was it water logged or water
damaged ... snip ...
 
I think he is talking about the rubber check valve on the input side of the filter.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
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