Home » Public Forums » GMCnet » Any warnings or things to do when replacing a mechanical fuel pump? (My carb is flooding out and running rich....)
Any warnings or things to do when replacing a mechanical fuel pump? [message #274827] |
Thu, 02 April 2015 17:28 |
budworks521
Messages: 137 Registered: October 2013 Location: Grand Rapids MI 1974 Pain...
Karma: 4
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I have tried numerous things to get the 455 running right. My carb has been totally rebuilt and I can get proper vaccuum when idling for 15 minutes or so then it just bogs out and the vac steadily decreases. I have tried timing, idle screws, vapor cannister, etc and still can't figure out my issue. I don't believe the float is damaged or the accelator pump is damaged. I experienced this flooding before the carb was rebuilt as well. Does anyone have any ideas what could increase the fuel pressure to the carb??? What about a damaged fuel line sucking air??? Anybody have any ideas. Thanks, btw this is pushing two years of an upper half rebuild. Fun.
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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Re: Any warnings or things to do when replacing a mechanical fuel pump? [message #274833 is a reply to message #274827] |
Thu, 02 April 2015 17:44 |
Bob de Kruyff
Messages: 4260 Registered: January 2004 Location: Chandler, AZ
Karma: 1
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budworks521 wrote on Thu, 02 April 2015 16:28I have tried numerous things to get the 455 running right. My carb has been totally rebuilt and I can get proper vaccuum when idling for 15 minutes or so then it just bogs out and the vac steadily decreases. I have tried timing, idle screws, vapor cannister, etc and still can't figure out my issue. I don't believe the float is damaged or the accelator pump is damaged. I experienced this flooding before the carb was rebuilt as well. Does anyone have any ideas what could increase the fuel pressure to the carb??? What about a damaged fuel line sucking air??? Anybody have any ideas. Thanks, btw this is pushing two years of an upper half rebuild. Fun. It sounds like you are pretty sure it is flooding and getting too much fuel. If it is, it's pretty difficult for a mechanical pump to supply too much pressure assuming it was the correct one in the first place. They are pretty cheap so replacing it is much easier if you remove the RH inner fender panel.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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Re: [GMCnet] Any warnings or things to do when replacing a mechanical fuel pump? [message #274838 is a reply to message #274833] |
Thu, 02 April 2015 17:55 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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Gee, it sounds like your carb problem is ignition module related. The
modules and mechanical fuel pumps are about the same price, and the module
is easier to change than the pump. As the engine warms up, the module
sometimes will act up, and then as the engine gets warmer than that, will
quit altogether. The coil will do the same thing. Ask Ken Henderson about
his issues that he thought were carb related. At least check for spark when
the engine quits the next time. If it isn't burning the fuel, it will mimic
carb flooding. Just saying.
Jim Hupy
Salem, Oregon
78 GMC ROYALE 403
On Apr 2, 2015 3:45 PM, "Bob de Kruyff" wrote:
> budworks521 wrote on Thu, 02 April 2015 16:28
>> I have tried numerous things to get the 455 running right. My carb has
> been totally rebuilt and I can get proper vaccuum when idling for 15
>> minutes or so then it just bogs out and the vac steadily decreases. I
> have tried timing, idle screws, vapor cannister, etc and still can't figure
>> out my issue. I don't believe the float is damaged or the accelator pump
> is damaged. I experienced this flooding before the carb was rebuilt as
>> well. Does anyone have any ideas what could increase the fuel pressure
> to the carb??? What about a damaged fuel line sucking air??? Anybody have
> any
>> ideas. Thanks, btw this is pushing two years of an upper half rebuild.
> Fun.
> It sounds like you are pretty sure it is flooding and getting too much
> fuel. If it is, it's pretty difficult for a mechanical pump to supply too
> much
> pressure assuming it was the correct one in the first place. They are
> pretty cheap so replacing it is much easier if you remove the RH inner
> fender
> panel.
>
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Re: [GMCnet] Any warnings or things to do when replacing a mechanical fuel pump? [message #274840 is a reply to message #274838] |
Thu, 02 April 2015 18:03 |
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Loffen
Messages: 1087 Registered: August 2013 Location: Norway
Karma: 1
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Good point there James, could be the module.
As in any carb adjustments, start with the ignition
James Hupy wrote on Fri, 03 April 2015 00:55Gee, it sounds like your carb problem is ignition module related. The
modules and mechanical fuel pumps are about the same price, and the module
is easier to change than the pump. As the engine warms up, the module
sometimes will act up, and then as the engine gets warmer than that, will
quit altogether. The coil will do the same thing. Ask Ken Henderson about
his issues that he thought were carb related. At least check for spark when
the engine quits the next time. If it isn't burning the fuel, it will mimic
carb flooding. Just saying.
Jim Hupy
Salem, Oregon
78 GMC ROYALE 403
On Apr 2, 2015 3:45 PM, "Bob de Kruyff" wrote:
> budworks521 wrote on Thu, 02 April 2015 16:28
>> I have tried numerous things to get the 455 running right. My carb has
> been totally rebuilt and I can get proper vaccuum when idling for 15
>> minutes or so then it just bogs out and the vac steadily decreases. I
> have tried timing, idle screws, vapor cannister, etc and still can't figure
>> out my issue. I don't believe the float is damaged or the accelator pump
> is damaged. I experienced this flooding before the carb was rebuilt as
>> well. Does anyone have any ideas what could increase the fuel pressure
> to the carb??? What about a damaged fuel line sucking air??? Anybody have
> any
>> ideas. Thanks, btw this is pushing two years of an upper half rebuild.
> Fun.
> It sounds like you are pretty sure it is flooding and getting too much
> fuel. If it is, it's pretty difficult for a mechanical pump to supply too
> much
> pressure assuming it was the correct one in the first place. They are
> pretty cheap so replacing it is much easier if you remove the RH inner
> fender
> panel.
>
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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1973 23' # 1848 Sky Blue Glacier called Baby Blue and a 1973 26'-3 # 1460 Parrot green Seqouia Known as the Big Green,
And sold my 1973 26'-2 # 581 White Canyon lands under the name Dobbelt trøbbel
in Norway
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Re: [GMCnet] Any warnings or things to do when replacing a mechanical fuel pump? [message #274842 is a reply to message #274838] |
Thu, 02 April 2015 18:02 |
Ray Erspamer
Messages: 1707 Registered: May 2007 Location: Milwaukee Wisconsin
Karma: -3
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Is your choke working properly?
Sent from my Verizon Wireless 4G LTE smartphone
-------- Original message --------
From: Lawrence Harrison
Date: 04/02/2015 5:28 PM (GMT-06:00)
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Any warnings or things to do when replacing a mechanical
fuel pump?
I have tried numerous things to get the 455 running right. My carb has been totally rebuilt and I can get proper vaccuum when idling for 15 minutes or
so then it just bogs out and the vac steadily decreases. I have tried timing, idle screws, vapor cannister, etc and still can't figure out my issue. I
don't believe the float is damaged or the accelator pump is damaged. I experienced this flooding before the carb was rebuilt as well. Does anyone have
any ideas what could increase the fuel pressure to the carb??? What about a damaged fuel line sucking air??? Anybody have any ideas. Thanks, btw this
is pushing two years of an upper half rebuild. Fun.
--
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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Re: Any warnings or things to do when replacing a mechanical fuel pump? [message #274844 is a reply to message #274827] |
Thu, 02 April 2015 18:58 |
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Matt Colie
Messages: 8547 Registered: March 2007 Location: S.E. Michigan
Karma: 7
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Oh Man Bud,
I wish you were a little closer than GR. (3+hours)
Bob is right. It is virtually impossible for the mechanical pump to supply too much pressure.
You See, they don't really pump, they suck... (lets not go there) They pull fuel in and then let a spring push the fuel on from there.
I have an "off the wall" for you.
Is a muffler blocked?? If one is and you idle for that long, you could be boiling the fuel in the carburetor because there is too much heat in the intake.
If you are going to check this, GET A FACE SHIELD <= Not a request,<= and run the engine with the air cleaner open. If you don't see fuel bubbling over and going into the engine, then that is not your problem.
If the vacuum is dropping, that could also be a crack in the intake that is opening up when things get hot.
Matt
budworks521 wrote on Thu, 02 April 2015 18:28I have tried numerous things to get the 455 running right. My carb has been totally rebuilt and I can get proper vaccuum when idling for 15 minutes or so then it just bogs out and the vac steadily decreases. I have tried timing, idle screws, vapor cannister, etc and still can't figure out my issue. I don't believe the float is damaged or the accelator pump is damaged. I experienced this flooding before the carb was rebuilt as well. Does anyone have any ideas what could increase the fuel pressure to the carb??? What about a damaged fuel line sucking air??? Anybody have any ideas. Thanks, btw this is pushing two years of an upper half rebuild. Fun.
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: Any warnings or things to do when replacing a mechanical fuel pump? [message #274881 is a reply to message #274827] |
Fri, 03 April 2015 10:58 |
Carl S.
Messages: 4186 Registered: January 2009 Location: Tucson, AZ.
Karma: 13
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budworks521 wrote on Thu, 02 April 2015 15:28I have tried numerous things to get the 455 running right. My carb has been totally rebuilt and I can get proper vaccuum when idling for 15 minutes or so then it just bogs out and the vac steadily decreases. I have tried timing, idle screws, vapor cannister, etc and still can't figure out my issue. I don't believe the float is damaged or the accelator pump is damaged. I experienced this flooding before the carb was rebuilt as well. Does anyone have any ideas what could increase the fuel pressure to the carb??? What about a damaged fuel line sucking air??? Anybody have any ideas. Thanks, btw this is pushing two years of an upper half rebuild. Fun.
Could your intake manifold possibly be cracked through to the floor? If this were the case, the crack may be opening up as the engine heats up, causing a vacuum leak from the lifter valley or the exhaust crossover.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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Re: Any warnings or things to do when replacing a mechanical fuel pump? [message #274939 is a reply to message #274827] |
Fri, 03 April 2015 18:07 |
budworks521
Messages: 137 Registered: October 2013 Location: Grand Rapids MI 1974 Pain...
Karma: 4
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I did have the intake off when rebuilding the upper half and it appeared normal? Had it bathed and no noticable cracks. I also did the exhaust manifold block off and the carb choke is about 95% open after I used Dick Patterson's suggestion of using a farmer's choke. It works but I can't tell if it is running too lean or too rich??? I am considering an electric choke that will maybe help the issue. Problem is I had it running great WITHOUT the farmer's choke installed after the rebuild and crossovers blocked. All the symptoms happened mid stream if you will, I could try the module but I had that tested and the coil tested and they came back good. I checked the wires as well. The cap and rotor have been replaced as well. I can go out and buy all kinds of stuff like a module, electric choke, etc and see if the thing starts running right. Maybe I should do that before I consider the fuel pump replacement. I did have some additives, sea foam, added to the gas to see if it would help solve it and that is why I think the diaprahm may be bad??? Thanks I will try some of the suggestions once it gets warmer out. Thanks gentlemnen.
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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Re: Any warnings or things to do when replacing a mechanical fuel pump? [message #275057 is a reply to message #274827] |
Sun, 05 April 2015 10:34 |
budworks521
Messages: 137 Registered: October 2013 Location: Grand Rapids MI 1974 Pain...
Karma: 4
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I already pulled the muffler off on the driver's side and was going to replace it. I have the new muffler waiting for install. The driver's bank intake is the side in question since it is quite evident that unspent fuel is burning on the intake manifold and blackening it. The driver's side is the side in question. It should be noted that a compression check reveals 129 to 137 ratings which Dick patterson says is normal for an engine with 135k on it. The exhaust manifolds are all new with copper gaskets.One progress I did make was when I plugged the line to the vapor cannister off the front of the carb that the dripping noise inside the manifold ceased. It used to sound like a popping noise inside the carb which has now stopped. Quite baffling. I sure wish I could find a local guy to assist me but that is a tall order or request. All this stuff happened after taking to a reputable service department snow balling ever since. I could yank the other muffler but not sure if ther exhaust is plugged. Thanks
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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Re: Any warnings or things to do when replacing a mechanical fuel pump? [message #275058 is a reply to message #274827] |
Sun, 05 April 2015 10:49 |
budworks521
Messages: 137 Registered: October 2013 Location: Grand Rapids MI 1974 Pain...
Karma: 4
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Matt, do you have any objections if I private message you or called you. The help would truly be appreciated and I know the area you live in quite well. I grew up in Roseville. Thanks
1974 Painted Desert
455 upper half rebuild
constant project inexperienced mechanic
Grand Rapids Mi
Always trying to learn
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Re: [GMCnet] Any warnings or things to do when replacing a mechanical fuel pump? [message #275110 is a reply to message #275066] |
Sun, 05 April 2015 22:03 |
Bob de Kruyff
Messages: 4260 Registered: January 2004 Location: Chandler, AZ
Karma: 1
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James Hupy wrote on Sun, 05 April 2015 11:12Larry, I was looking back over your original question regarding replacement
of a mechanical fuel pump. Realized that we have strayed a tiny bit off of
that, so I had a thought that no one had mentioned that when you have the
pump off, you ought to use a piece of 1/8 " welding rod or plain old
bailing wire with a "j" bent in the very end to get a hold of the timing
chain to check for excessive slack in the chain. 1/8 to 3/16" movement in
the chain while pulling and pushing with the hook is normal. Any more than
that indicates a worn chain and something to keep your eye on. If there is
a great deal of slack, 1/2" or more, you might need a new set of chain and
sprockets pretty soon. This will account for retarded cam timing, and
erattic ignition timing as well because the distributor gear is driven with
the cam, and slack, or more accurately slap in the chain will cause that.
Jim Hupy
a couple of other easy items to check:
Is your fuel tank venting properly? you might try loosening the gas cap
to see if it makes any difference.
is your mechanical spark advance working properly?
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Now that's a keeper for all of us!
Bob de Kruyff
78 Eleganza
Chandler, AZ
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