tonym2180
davie
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Joined: 02/02/2012
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I have an 82 winnebago 29 454 4bbl,just did full tuneup,cap,coil,plugs,wires module,capacitor and harness,I also check the weights ,springs and vacuum advance.fuel filters...one on the inlet of the carb and one on the frame. The gas tank was dropped and cleaned and all new rubber hoses from back to front. At that time the mechanical fuel pump was also replaced,it also has a inline electric pump as well. The problem with it is it runs and drives great around town but soon as I attempt to get on the highway it loses all power,kinda feels like its not getting any gas.no backfiring or anything just fall flat,if I pull over rev it up and take off slowly it regains power. I drove it with the air cleaner off and it looks like its functioning properly all 4 barrels open when I stomp it from a dead stop and the secondaries aren't flopping open but when I put the air cleaner back on and get on the highway it fall flat .any suggestion would be Awsome. Tony
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1995brave
San Antonio, TX
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Joined: 01/24/2006
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Put a vacuum gauge, fuel pressure guage, and a tach on it and go for a test drive on the freeway. Watch them and see which one drops out first. I would say you have a vacuum leak or the timing is off.
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Mustang7370
Washington State
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Joined: 12/10/2011
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Well, It kind of sounds like you may have some restricted exhaust. Perhaps a plugged catalyst (if it has one) or maybe the muffler has collapsed internally. If it is possible, disconnect the muffler from the exhaust and drive it, or better yet, there are exhaust backpressure testing kits out there that require drilling a small hole in the exhaust headpipe and installing a temporary fitting that attaches to a pressure gauge with a long hose. Anything over 5 PSI is asking for trouble.
The other thing I have seen is some brass fuel bleed tubes falling out of the top of the carburetor and landing in the pockets in which they reside. To check this requires removal and disassembly of the carburetor. If I find these, I just put them back in the top of the carburetor and lightly stake them in place.
I am leaning more toward backpressure though. Lean conditions will usually create spark knock and backfire thru carb. Another possibility is a timing chain that has jumped a tooth.
Ugh, I know.. so many things. I will follow your post in case there are more questions. Good luck
Chris and Kelli Withers
Ferndale, WA.
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tonym2180
davie
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It has a vacuum gauge and a tach. Vacuum does drop off when it boggs out I did go through all the vacuum lines,I was thinking the pulloff for the choke might not be working properly.it has no cats on exhaust and it seems to be breathing fine,it has mufflers with dumps and it you mash the gas it leaves holes in the dirt,I will check timing and fuel pressure this weekend being as it is not close to my house. For some reason I'm leaning toward vaccuum or carb related but I will take any suggestions, I forgot to say it doesn't always do it sometimes she will run fine all day long,if it jumped timing it would run like******constantly
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enblethen
Moses Lake, WA
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Joined: 01/05/2005
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Check for a vacuum operated heat riser on right side of engine. It may not be operating causing ecess back-up in exhaust.
Bud
USAF Retired
Suzuki XL7 pushing Pace Arrow
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tonym2180
davie
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That's why the exhaust gas is coming through the breather heavily on the right valve cover going to the air cleaner I think its choking the carb out, when I ran it today without the air cleaner it didn't fall or hesitate one bit.I think you may be on to something
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ssia2485
Tampa FL
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Joined: 05/17/2011
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The quadrajets have a very small fuel bowl. if you have a weak fuel pump it will starve for fuel. Install a good high volume pump and you wont have any problems. also if the carb has been rebuilt the float level might be set too low. Also you will want to check the damper for the secondaries, if the diaphram is shot it will allow the secondary air flap to open to quick and cause the big bog that the q-jets are famous for. There is not a better carb once you get one working good.
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tonym2180
davie
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It has a brand new mechanical and electric fuel pump,don't know if the carb has been rebuilt but I ran it with the doghouse and air cleaner off and the secondaries worked perfect,I'm kind of leaning towards the heat riser but I will check fuel pressure, timing and anything you guys can steer me towards.thanks for all of your responses and I'm open to more. Keep em coming
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Mustang7370
Washington State
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tonym2180 wrote:That's why the exhaust gas is coming through the breather heavily on the right valve cover going to the air cleaner I think its choking the carb out, when I ran it today without the air cleaner it didn't fall or hesitate one bit.I think you may be on to something
Exhaust gas out the right valve cover breather?? That should not be happening. That should be crankcase fumes coming out of there!
Wait! Does this thing have air injection? I bet you blew a check valve and its allowing exhaust gas to be pumped into the air cleaner. That should not be happening and will definitely kill your power like an EGR valve being stuck wide open.
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tonym2180
davie
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Check valve? Please explain
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