I THINK I AM THROWING IN THE TOWEL

One of those replacement mech fuel pumps rusted from the inside out.
It was when I used an electric fuel pump to pump fuel to the Mech fuel pump,
which then fuel picked up the rust ( I don't think the Mech pump was pumping as
all the inerds were rusted badly), and that rust got through the Carborator
filter, and contaminated the inside of the carborator. This was carb
#3.
Obviously the mech fuel pump was junk and the carb was not repairable.

This senario started with those carbs with the fuel bowl that had those blocked
holes in the bottom.
When sitting, the fuel dripped from the bowl, then air was allowed in and down the system
to the Mech fuel pump which started the rusting.
We cut the mech fuel pump open because the fuel filter before it was clean, but
the Mech fuel pump was rusted fully inside and junk.
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
Completely understanable....bypass the works with the e-pump and give it a go as you have nothing to loose and all to gain. Worse case change the carb
for anything that you know works the get it to someone who knows the ropes....who cars if the hatch is open a bit.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
> Completely understanable....bypass the works with the e-pump and give it a go as you have nothing to loose and all to gain. Worse case change the
> carb for anything that you know works the get it to someone who knows the ropes....who cars if the hatch is open a bit.

Yes, I am still stunned at how fast this died. Like in hours it went from fully functioning to a tow ride home. sheesh.
I am stunned.

I am not looking at this really close right now, I need to let the shock wear off first.

But, my mind won't drop it. I may not have it right, but it seems the only thing that can have common connection, and this is
putting the fuel tanks and hoses to the side and out of the picture, is the mech fuel pump.

Before I could use the external gas can and run fine simply with gravity feed, this time, it didnt make a difference.

So the first attack may be an external electric fuel pump, and by pass the mech pump.

that may be my first option..

thanks for the thought
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
When you are not the mechanic doing the work it’s tough to decide what went wrong. My carburetor was having some vapor lock problems. What I did was
drop the tanks and install all new lines And removed the socks from the pickup and extended them about a half inch, removed the mechanical pump and
the switch over valve installed a carter electric pump and larger fuel filter for each tank on the outside of the frame near the tanks insulated the
fuel lines and piped to the carburetor from the rear of the engine instead of the front. Put shields between the tanks and exhaust also put insulating
paint on the outside of the tanks. That stopped the vapor lock problems and I knew it was done right cause I’m the guy doing the work if it’s not
your labor it isn’t always easy to know if it was done right. Don’t forget the check valves for each pump. Good luck hope you find the problem.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
In a private email to Stan I suggested he verify that the fuel filter in the carb is not reversed.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> In a private email to Stan I suggested he verify that the fuel filter in the carb is not reversed.

I also suggested a fuel pressure sender attached to the line and reading the pressure when it fails. If the pressure is good and the carb filter is
OK, then we are looking at ignition problems or low battery voltage.

Being it is a 74 it probably has a points system and possibly a bad condenser or heat sensitive coil. All of this is just guessing without knowing
the fuel pressure at the carb at the time of failure.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> > In a private email to Stan I suggested he verify that the fuel filter in the carb is not reversed.
>
> I also suggested a fuel pressure sender attached to the line and reading the pressure when it fails. If the pressure is good and the carb filter
> is OK, then we are looking at ignition problems or low battery voltage.
>
> Being it is a 74 it probably has a points system and possibly a bad condenser or heat sensitive coil. All of this is just guessing without
> knowing the fuel pressure at the carb at the time of failure.


Yes, the GMC is a 1974 and when I bought it, it had points and coil system ignition. After the Tanks and Hoses were checked and replaced the hoses,
the power problem began its existance. The shop tried changing the carbs, incuding 3 rebuilt carbs which all did not correct the problem, replaced
the distributor shaft and put electronic Ign on. Nothing improved the problem permanently.
As I recall, after filling up heading home, this was directly leaving the shop, My top speed was 55 and by the time I reached Chicago, top speed was
down to 35 mph. After that, the long sorry saga of trying to find and correct the problem began. I bet the mechanic was sorry he agreed to help me
out on this because over the years there have been few wins and mostly failures. And now, here we are..........

Thanks all for your ideas. It sucks to be still in this situation all these years after it started.

OK so I will give it a try, I plan to ignore the existing fuel tanks and hoses as these are the known problem and something must have gotten worse
for the electric fuel pump to not be able to keep me going.

I am going to by pass the Mech fuel pump and add an electric fuel pump and use external gas tank and see if there are any good results.

I am of course keeping in mind and will test out many of your suggestions. Many of these thoughts I have already done but as you know, we are back to
the condition when it all started.

This is feeling very futile at this point and she is not far from becoming a garden ornament, but I will try to persist.

Thanks all for the confidence and ideas.


--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
> I'd suggest springing for a FI system and forget the carb. You'll have to be sure you have fuel from the tanks but running seperate lines from the
> tanks with dual pumps and no switch over valve is a pretty sure fix. Hate to see you give up on your dream.
> Hal

I have heard of problems with the FI systems as well and they are more complicated to set up.

This problem is not carborator related, at least not that I can tell. It is fuel supply related.
Everything we have done has been to increase fuel flow and that always corrected the power loss problem.
Adding FI would be among the last of the considerations but I do not believe it will correct anything.
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
> When you are not the mechanic doing the work it’s tough to decide what went wrong. My carburetor was having some vapor lock problems. What I did
> was drop the tanks and install all new lines And removed the socks from the pickup and extended them about a half inch, removed the mechanical pump
> and the switch over valve installed a carter electric pump and larger fuel filter for each tank on the outside of the frame near the tanks insulated
> the fuel lines and piped to the carburetor from the rear of the engine instead of the front. Put shields between the tanks and exhaust also put
> insulating paint on the outside of the tanks. That stopped the vapor lock problems and I knew it was done right cause I’m the guy doing the work
> if it’s not your labor it isn’t always easy to know if it was done right. Don’t forget the check valves for each pump. Good luck hope you find
> the problem.

THE THOUGHT OF VAPOR LOCK
Vapor lock can be a problem, I am thinking it is not this problem. Vapor lock, as my thoughts goe, happens when the fuel gets hot and that crap
alcohol flashes causing the fuel to not supply the carb properly. It has to get hot. I have this problem wether the engine is hot or cold.

If I am thinking wrong, do correct me.

someone once had me almost convinced that vapor lock might be the cause and I had designed a tank that would send that excess gas back to the vent
system and send only fuel to the carb. A tank set up like this I view as risky as you are adding more lines and connections were fuel line connects
to fittings. More risk and as GMCs like to catch fire, I thought it may be wise to go any other way to try to prevent adding more risk opportunity of
fire to the coach.

I think I still have that tank design and if it should be a concern again, I may have to actually build that tank and go from there.

My line from the Mech fuel pump to the Carb filter was changed out to an insulated version to help prevent heat from building up. My fuel line from
the solenoid fuel valves to the mechanical fuel pump is new hose and has been run to stay away, as best we can from heat sources. Obviously, road
heat is difficult to get around but we do what we can.
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
My friend’s car parts business is in Waukegan. I get there once in a while. I could at least look to see if there is something obviously wrong. I
have a perfectly good spare 77 Qjet but sounds like if 3 carbs have been tried it might be ignition.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
> My friend’s car parts business is in Waukegan. I get there once in a while. I could at least look to see if there is something obviously wrong.
> I have a perfectly good spare 77 Qjet but sounds like if 3 carbs have been tried it might be ignition. How many miles on your timing gear/chain set?

I dont know...............
To qualify that poor answer, when I bought the GMC, the PO that used it for a flip, told me he had the engine overhauled and that the motor had just
been tuned up. BUT there was no paperwork to prove either of these claims.

ok so I have this GMC motorhome and I am driving home, it begins to run rough, I pull into a town where there is a GMC dealer. They said they can
look at it. They found the distributor shaft was so worn that the timing could not be set.

They replaced the distributor shaft with a stock Olds distributor. The timing was set and she ran sweet all the way home, about 1000 miles.

The speedometer indicates 33k plus miles and since this may be the original timing gear/chain, it most likely is original with 133,000 miles.

the GMC is now sitting at the mechanics garage, and I can't wait to tell him that we are back to day one of the problems. He will be so thrilled.

It most likely will be there for awhile, so you'd be seeing it on his site. Just let me know when you might want to stop by to look.
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
If it really is 133 K miles could this be a case of the timing chain finally skipping at least 1 tooth ? There have
been a few methods posted a checking timing chain slack/tension without serious taking apart. Might a reasonable place to start
be, is the rotor in the distributor in the right place when cylinder #1 is at TDC on the firing stock? Step 2, if step 1
is OK, we need someone to post the easiest way to check timing chain slack without serious dissasembly Ken B or Matt C, any ideas
here? Everyone feel free to chime in.

--
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
 
If you do change the mechanical fuel pump, after you remove it, use a
straight piece of solid wire (wire coat hanger is fine) about 10 -12 inches
in length. With needle nose pliers, bend a "J" hook on the end. Reach in
the open port where the fuel pump goes, and hook the timing chain. Pull it
towards you, then push it back in. If you have more than 3/8" of travel
slack, your chain has excessive stretch wear and need replacement.
Jim Hupy
Salem, Oregon

On Mon, Jul 27, 2020, 11:28 AM Dave King via Gmclist <

> If it really is 133 K miles could this be a case of the timing chain
> finally skipping at least 1 tooth ? There have
> been a few methods posted a checking timing chain slack/tension without
> serious taking apart. Might a reasonable place to start
> be, is the rotor in the distributor in the right place when cylinder #1 is
> at TDC on the firing stock? Step 2, if step 1
> is OK, we need someone to post the easiest way to check timing chain slack
> without serious dissasembly Ken B or Matt C, any ideas
> here? Everyone feel free to chime in.
>
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I would really like to see a fuel pressure gauge for diagnostic purposes
just after the fuel pump.

On Mon, Jul 27, 2020 at 1:01 PM James Hupy via Gmclist <

> If you do change the mechanical fuel pump, after you remove it, use a
> straight piece of solid wire (wire coat hanger is fine) about 10 -12 inches
> in length. With needle nose pliers, bend a "J" hook on the end. Reach in
> the open port where the fuel pump goes, and hook the timing chain. Pull it
> towards you, then push it back in. If you have more than 3/8" of travel
> slack, your chain has excessive stretch wear and need replacement.
> Jim Hupy
> Salem, Oregon
>
> On Mon, Jul 27, 2020, 11:28 AM Dave King via Gmclist <

>
> > If it really is 133 K miles could this be a case of the timing chain
> > finally skipping at least 1 tooth ? There have
> > been a few methods posted a checking timing chain slack/tension without
> > serious taking apart. Might a reasonable place to start
> > be, is the rotor in the distributor in the right place when cylinder #1
> is
> > at TDC on the firing stock? Step 2, if step 1
> > is OK, we need someone to post the easiest way to check timing chain
> slack
> > without serious dissasembly Ken B or Matt C, any ideas
> > here? Everyone feel free to chime in.
> >
> > --
> > DAVE KING
> > lurker, wannabe
> > Toronto, Ontario, Canada
> >
> > _______________________________________________
> > 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
>

--

*John Phillips*
 
> If you do change the mechanical fuel pump, after you remove it, use a
> straight piece of solid wire (wire coat hanger is fine) about 10 -12 inches
> in length. With needle nose pliers, bend a "J" hook on the end. Reach in
> the open port where the fuel pump goes, and hook the timing chain. Pull it
> towards you, then push it back in. If you have more than 3/8" of travel
> slack, your chain has excessive stretch wear and need replacement.
> Jim Hupy
> Salem, Oregon
>
> On Mon, Jul 27, 2020, 11:28 AM Dave King via Gmclist <

>
> > If it really is 133 K miles could this be a case of the timing chain
> > finally skipping at least 1 tooth ? There have
> > been a few methods posted a checking timing chain slack/tension without
> > serious taking apart. Might a reasonable place to start
> > be, is the rotor in the distributor in the right place when cylinder #1 is
> > at TDC on the firing stock? Step 2, if step 1
> > is OK, we need someone to post the easiest way to check timing chain slack
> > without serious dissasembly Ken B or Matt C, any ideas
> > here? Everyone feel free to chime in.
> >
> > --
> > DAVE KING
> > lurker, wannabe
> > Toronto, Ontario, Canada
> >
> > _______________________________________________
> > 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

Thank you

--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
> If it really is 133 K miles could this be a case of the timing chain finally skipping at least 1 tooth ? There have
> been a few methods posted a checking timing chain slack/tension without serious taking apart. Might a reasonable place to start
> be, is the rotor in the distributor in the right place when cylinder #1 is at TDC on the firing stock? Step 2, if step 1
> is OK, we need someone to post the easiest way to check timing chain slack without serious dissasembly Ken B or Matt C, any ideas
> here? Everyone feel free to chime in.

ok QUESTION
If the timing chain had skipped a tooth, wouldn't the engine run terribly all the time, miss, etc?????????

I ask this because until the power loss happens, 27 to 32 mph, the engine fires up and RPMs climb just like normal, strong, smooth.

I am thinking if the timing is messed up, it would not have that smooth strong power build up, RPM climb in the beginning from low RPM up.

---

OK so at a full stop, engine running, brakes on. the engine runs at good idle, strong, no missing. Press the accellerator down, the engine will
raise the RPM normally, no missing, strong climb until it reaches that 20- +, when it get to that point, the power loss happens. But if the RPMS
go down, the engine smooths out and I press the pedal, the engine reves up to the point where the power loss occurs. then repeat the above again.

This is more or less exactly what I experienced, more or less, after I left that shop when the Tanks and hoses were changed all those years back. I
have had her running at 75 mph since until this happened again.

I do not believe the chain would slip BACK into normal position on the gear.

But I will try a couple things and if it gets more rediculous, will try to check the timing chain too.

thanks you all.
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center
 
slc,

You've gotten LOTS of advice, most of it good, some excellent. I'm goint
to tell you what I'd do:

First I'd be sure the electric fuel pump is OFF. Then I'd disconnect and
plug the short rubber coupling between the fuel tank supply line and that
leading to the mechanical fuel pump, thereby disabling all of the GMC's
fuel system. That coupling's at the right front side of the 2nd (main)
chassis crossmember.

Since I have a 5 gallon "jerry can" with an attached electric fuel pump,
I'd set that on the front bumper, and connect it with rubber tubing to the
carburetor with a short metal adapter. However, you said you've used a
gravity fed system in the past -- do it again, 'though I'm surprised you
get enough fuel pressure & volume to support much engine load.

Drive enough with that replacement fuel system to convince yourself that
you've eliminated the problem; I'm confident that will prove true.

If it IS a fuel problem, get those tanks down again if possible to be sure
all the lines are properly attached, routed, and undamaged. REMOVE the
"socks" from the fuel pickup tubes. I'd suggest replacing all the rubber
lines with 3/8" steel while the tanks are down, but it's not mandatory. DO
check whatever tubes you install for clear flow.

With the tanks back in place, remove and sell to some other sucker that
fuel selector valve -- it's nothing but a problem waiting to happen, IMHO.
You haven't said what kind of electric fuel pump you're using, but it's
apparently OK. I personally use nothing but Carter 4070's for low
pressure. With large, easily accessible inline fuel filters BEFORE the two
fuel pumps, combine their outputs with a tee into the hard line leading
forward. While the 4070 does not require them, I install check valves at
the inputs the tee just in case I have an emergency need to install a pump
which requires them.

With a 12VDC SPDT relay controlled by the wire originally serving the
selector valve, supply the two electric pumps with independent 12VDC power
through a circuit breaker and a low oil pressure switch (or other safety
shutoff), using at least 16 gauge wire.

With that fuel system, there's hardly any chance of your experiencing fuel
starvation. And if you do, by simply switching the Tank Selector switch to
the other tank, you'll transfer about 95% of the fuel supply system to
different components. You'll probably never experience fuel starvation
again, even from vapor lock.

The redundancy is more than worth the slight additional cost of the 2nd
pump vs that of the selector valve.

JMHO & JWID (Just What I've Done),

Ken H.

On Mon, Jul 27, 2020 at 8:10 PM slc via Gmclist
wrote:

> > If it really is 133 K miles could this be a case of the timing chain
> finally skipping at least 1 tooth ? There have
> > been a few methods posted a checking timing chain slack/tension without
> serious taking apart. Might a reasonable place to start
> > be, is the rotor in the distributor in the right place when cylinder #1
> is at TDC on the firing stock? Step 2, if step 1
> > is OK, we need someone to post the easiest way to check timing chain
> slack without serious dissasembly Ken B or Matt C, any ideas
> > here? Everyone feel free to chime in.
>
>
>
> ok QUESTION
> If the timing chain had skipped a tooth, wouldn't the engine run
> terribly all the time, miss, etc?????????
>
> I ask this because until the power loss happens, 27 to 32 mph, the
> engine fires up and RPMs climb just like normal, strong, smooth.
>
> I am thinking if the timing is messed up, it would not have that smooth
> strong power build up, RPM climb in the beginning from low RPM up.
>
> ---
>
> OK so at a full stop, engine running, brakes on. the engine runs at good
> idle, strong, no missing. Press the accellerator down, the engine will
> raise the RPM normally, no missing, strong climb until it reaches that 20-
> +, when it get to that point, the power loss happens. But if the RPMS
> go down, the engine smooths out and I press the pedal, the engine reves up
> to the point where the power loss occurs. then repeat the above again.
>
> This is more or less exactly what I experienced, more or less, after I
> left that shop when the Tanks and hoses were changed all those years back.
> I
> have had her running at 75 mph since until this happened again.
>
> I do not believe the chain would slip BACK into normal position on the
> gear.
>
> But I will try a couple things and if it gets more rediculous, will try to
> check the timing chain too.
>
> thanks you all.
> --
> GatsbysCruise. \
> 74GMC260 Former Glacier Model style. \
> Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS
> FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
> UBUNTU VOYAGER - Berzin Auto Center
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I agree with all that Ken H has stated. However when you run your test using the auxiliary 5 gallon tank I would also remove the filter going into the carburetor.

Sent from my iPad

>
> slc,
>
> You've gotten LOTS of advice, most of it good, some excellent. I'm goint
> to tell you what I'd do:
>
> First I'd be sure the electric fuel pump is OFF. Then I'd disconnect and
> plug the short rubber coupling between the fuel tank supply line and that
> leading to the mechanical fuel pump, thereby disabling all of the GMC's
> fuel system. That coupling's at the right front side of the 2nd (main)
> chassis crossmember.
>
> Since I have a 5 gallon "jerry can" with an attached electric fuel pump,
> I'd set that on the front bumper, and connect it with rubber tubing to the
> carburetor with a short metal adapter. However, you said you've used a
> gravity fed system in the past -- do it again, 'though I'm surprised you
> get enough fuel pressure & volume to support much engine load.
>
> Drive enough with that replacement fuel system to convince yourself that
> you've eliminated the problem; I'm confident that will prove true.
>
> If it IS a fuel problem, get those tanks down again if possible to be sure
> all the lines are properly attached, routed, and undamaged. REMOVE the
> "socks" from the fuel pickup tubes. I'd suggest replacing all the rubber
> lines with 3/8" steel while the tanks are down, but it's not mandatory. DO
> check whatever tubes you install for clear flow.
>
> With the tanks back in place, remove and sell to some other sucker that
> fuel selector valve -- it's nothing but a problem waiting to happen, IMHO.
> You haven't said what kind of electric fuel pump you're using, but it's
> apparently OK. I personally use nothing but Carter 4070's for low
> pressure. With large, easily accessible inline fuel filters BEFORE the two
> fuel pumps, combine their outputs with a tee into the hard line leading
> forward. While the 4070 does not require them, I install check valves at
> the inputs the tee just in case I have an emergency need to install a pump
> which requires them.
>
> With a 12VDC SPDT relay controlled by the wire originally serving the
> selector valve, supply the two electric pumps with independent 12VDC power
> through a circuit breaker and a low oil pressure switch (or other safety
> shutoff), using at least 16 gauge wire.
>
> With that fuel system, there's hardly any chance of your experiencing fuel
> starvation. And if you do, by simply switching the Tank Selector switch to
> the other tank, you'll transfer about 95% of the fuel supply system to
> different components. You'll probably never experience fuel starvation
> again, even from vapor lock.
>
> The redundancy is more than worth the slight additional cost of the 2nd
> pump vs that of the selector valve.
>
> JMHO & JWID (Just What I've Done),
>
> Ken H.
>
>> On Mon, Jul 27, 2020 at 8:10 PM slc via Gmclist

>>

>>> If it really is 133 K miles could this be a case of the timing chain
>> finally skipping at least 1 tooth ? There have
>>> been a few methods posted a checking timing chain slack/tension without
>> serious taking apart. Might a reasonable place to start
>>> be, is the rotor in the distributor in the right place when cylinder #1
>> is at TDC on the firing stock? Step 2, if step 1
>>> is OK, we need someone to post the easiest way to check timing chain
>> slack without serious dissasembly Ken B or Matt C, any ideas
>>> here? Everyone feel free to chime in.
>>
>>
>>
>> ok QUESTION
>> If the timing chain had skipped a tooth, wouldn't the engine run
>> terribly all the time, miss, etc?????????
>>
>> I ask this because until the power loss happens, 27 to 32 mph, the
>> engine fires up and RPMs climb just like normal, strong, smooth.
>>
>> I am thinking if the timing is messed up, it would not have that smooth
>> strong power build up, RPM climb in the beginning from low RPM up.
>>
>> ---
>>
>> OK so at a full stop, engine running, brakes on. the engine runs at good
>> idle, strong, no missing. Press the accellerator down, the engine will
>> raise the RPM normally, no missing, strong climb until it reaches that 20-
>> +, when it get to that point, the power loss happens. But if the RPMS
>> go down, the engine smooths out and I press the pedal, the engine reves up
>> to the point where the power loss occurs. then repeat the above again.
>>
>> This is more or less exactly what I experienced, more or less, after I
>> left that shop when the Tanks and hoses were changed all those years back.
>> I
>> have had her running at 75 mph since until this happened again.
>>
>> I do not believe the chain would slip BACK into normal position on the
>> gear.
>>
>> But I will try a couple things and if it gets more rediculous, will try to
>> check the timing chain too.
>>
>> thanks you all.
>> --
>> GatsbysCruise. \
>> 74GMC260 Former Glacier Model style. \
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> OK so at a full stop, engine running, brakes on. the engine runs at good idle, strong, no missing. Press the accellerator down, the engine will
> raise the RPM normally, no missing, strong climb until it reaches that 20- +, when it get to that point, the power loss happens. But if the RPMS
> go down, the engine smooths out and I press the pedal, the engine reves up to the point where the power loss occurs. then repeat the above again.
>
> This is more or less exactly what I experienced, more or less, after I left that shop when the Tanks and hoses were changed all those years back.
> I have had her running at 75 mph since until this happened again.
>
>
> thanks you all.

On our 1300 mile trip home when we bought our current GMC we experienced multiple instances just like what you are describing.
The reason for our problem was the filter in the carb and the can filter down by the electric fuel pump. I had to change both
multiple times on the way home. We do not have a mechanical fuel pump just the electric pump. It might not be filters in your case
but something is restricting the flow of fuel.
--
Tom Lins
St Augustine, FL
77 GM Rear Twin, Dry Bath, 455, Aluminum Radiator Quad-Bag Suspension Solar Panel
Manuals on DVD
GMC Dealer Training Tapes
http://www.bdub.net/tomlins/
 
Yes if chain is lose or skipped it will be a dog at all times and have a very distinctive sound like a sick duck when you get on it. The Qjet will
wail with little increase in speed. . If it pulls then goes flat it’s a fuel issue. If you kill the ignition when it goes flat then see if there
is gas in carb via pump squirt we can accomplish the diagnosis without even getting finger nails dirty
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
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