Help!! Carb, fuel system issue?
Thread Starter
Cruising
Joined: Sep 2006
Posts: 13
Likes: 0
From: Pittsburgh Pa
Help!! Carb, fuel system issue?
What a minute, this sounds all too familiar. I just purchased a 1973 vette, 350 automatic, and am having the same problems. After idling fine, heading up a hill or looking to hit the throttle, the car appears to bog out as if it no longer is getting gas. I had a mechanic replace the fuel pump, fuel lines, fuel filter, and even drain most of the gas. It appears that someting is clogging the line at different times, or... carb issues.
I have twice removed a rubber gas line to the carb, blown air through it back to the gas tank, reinstalled and then the engine runs great for the next few minutes, until eventually, I need that full horse power and it again, appears to bog out by not getting gas effectively and accurately. The only way I was able to get up a hill the other day was in reverse.
I have waited a long time to get a vette, and want to hit the road with it before the winter comes in a month. (Pittsburgh, PA).
Any ideas, sending unit, carb issue?
Much appreciated any help.
I have twice removed a rubber gas line to the carb, blown air through it back to the gas tank, reinstalled and then the engine runs great for the next few minutes, until eventually, I need that full horse power and it again, appears to bog out by not getting gas effectively and accurately. The only way I was able to get up a hill the other day was in reverse.
I have waited a long time to get a vette, and want to hit the road with it before the winter comes in a month. (Pittsburgh, PA).
Any ideas, sending unit, carb issue?
Much appreciated any help.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
The next time it happens, undo the rubber line to your carb and put it into a milk jug and crank engine over. See if you get gas flow. If you do then put a pressure gauge on it and crank to test pump.
Gives you a plce to start.
Gives you a plce to start.
Thread Starter
Cruising
Joined: Sep 2006
Posts: 13
Likes: 0
From: Pittsburgh Pa
This helps
If the pressure is weak or non existant and gas is not flowing after cranking it over, then I presume the thought is that it may not be the carb, but the fuel pump (although I replaced this the other day), or maybe the fuel sending unit or something in the line?
I appreciate the help. New corvette owner and need to hit the road with it. If I knew how to send pictures, I would send one.
I appreciate the help. New corvette owner and need to hit the road with it. If I knew how to send pictures, I would send one.
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
try driving the car with the gas cap loose or off, if the canister/gas tank vent system is plugged you can not get air into the gas tank to replace the fuel as the engine uses it. a fuel pump can not pump fuel from the tank if the tank has a vacuum in it.
henry @ oles carb
henry @ oles carb
Racer
Joined: Mar 2006
Posts: 366
Likes: 1
From: Houston Texas
It is the plunger/piston in the carb that is part of the primary jet/rod control circuit (i've assumed you have a qjet?).
Here is a link:
http://www.corvettefever.com/howto/53360/
Here is a link:
http://www.corvettefever.com/howto/53360/
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Drifting
Joined: Feb 2005
Posts: 1,438
Likes: 2
From: Melrose Florida
What Henry Oles said about vapor lock...
or, the filter in the carb inlet is OFTEN overlooked, and they do plug. Should be a paper pleated filter, maybe a frit-type stone.
Steve
"power pump" sounds like accelerator pump, usually just limits hard acceleration if bad...should still be able to climb a hill.
Try the loosened or a vented cap.
or, the filter in the carb inlet is OFTEN overlooked, and they do plug. Should be a paper pleated filter, maybe a frit-type stone.
Steve
"power pump" sounds like accelerator pump, usually just limits hard acceleration if bad...should still be able to climb a hill.
Try the loosened or a vented cap.
Thread Starter
Cruising
Joined: Sep 2006
Posts: 13
Likes: 0
From: Pittsburgh Pa
Ok, here was tonight's test and what to make of it.
After draining the gas tank to the best of my ability, I noticed some discolorization, maybe water, definately a little rusty in the gas tank.
So, I hook up a 1 gallon gas can at the wheel well directly to the fuel pump, and the car runs great. I did this about 6 times, finishing up a gallon of gas each time. No problems of course until I ran out of gas, which was rather quick. Accelerating, hills, hitting the throttle good. Runs great.
What is the problem then from the fuel pump back to the tank? Bad gas in the tank, rust, water? Time to drain the tank and clean it out? The "sock" looks good in the tank. I even clean it off some last time.
Or could there be another problem to consider?
Also, what kind of gas mileage can I expect from my 350 automatic? Seems like I was dropping a gallon of gas a lot quicker than normal. Which may be due to the goofy hook up of a gallon gas can on the wheel well.
After draining the gas tank to the best of my ability, I noticed some discolorization, maybe water, definately a little rusty in the gas tank.
So, I hook up a 1 gallon gas can at the wheel well directly to the fuel pump, and the car runs great. I did this about 6 times, finishing up a gallon of gas each time. No problems of course until I ran out of gas, which was rather quick. Accelerating, hills, hitting the throttle good. Runs great.
What is the problem then from the fuel pump back to the tank? Bad gas in the tank, rust, water? Time to drain the tank and clean it out? The "sock" looks good in the tank. I even clean it off some last time.
Or could there be another problem to consider?
Also, what kind of gas mileage can I expect from my 350 automatic? Seems like I was dropping a gallon of gas a lot quicker than normal. Which may be due to the goofy hook up of a gallon gas can on the wheel well.
Last edited by Daniel James23; Sep 12, 2006 at 09:37 AM.
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
Originally Posted by Daniel James23
Also, what kind of gas mileage can I expect from my 350 automatic?
J.P. Morgan used to say about yachts "If you have to ask you can't afford it". If yours is like mine, about 12 miles/gal. 
the kind of gas mileage the oil companies have wet dreams about. Happy driving. 
Instructor
Joined: Apr 2005
Posts: 136
Likes: 41
From: Arvada CO
I had a very similar problem a while back. My problem was the rubber hose from the tank to the hard line on the frame. The return and supply lines were crossed and the supply line was crimped. I dropped the tank and put new hoses on and it cleared up. Hope this helps. See thread below.
http://forums.corvetteforum.com/show....php?t=1322607
http://forums.corvetteforum.com/show....php?t=1322607
Thread Starter
Cruising
Joined: Sep 2006
Posts: 13
Likes: 0
From: Pittsburgh Pa
Good point. I had the supply line changed though the other day. It was a real soft rubber and thought maybe it was squezzing shut. But, I did not check the return line. Only the supply line to the frame. What exactly is the role of the return line, where is this located in relation to the supply line? Could this create a vacuum problem?
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
There is also a filter on the pick-up tube inside the tank called the sock. Over time it breaks down and collapes over the inlet blocking flow.
Also check for the vapor cannister. If you have one and it is hooked up correctly you should use a non vented cap. If you don't have one either from the factory or has been removed and the hoses plugged you must use a vented cap.
Be sure you are using the molded fuel hose from the frame to the pump. Bulk hose often crimps.
Mike
Also check for the vapor cannister. If you have one and it is hooked up correctly you should use a non vented cap. If you don't have one either from the factory or has been removed and the hoses plugged you must use a vented cap.
Be sure you are using the molded fuel hose from the frame to the pump. Bulk hose often crimps.
Mike
Thread Starter
Cruising
Joined: Sep 2006
Posts: 13
Likes: 0
From: Pittsburgh Pa
Originally Posted by tracdogg2
There is also a filter on the pick-up tube inside the tank called the sock. Over time it breaks down and collapes over the inlet blocking flow.
Also check for the vapor cannister. If you have one and it is hooked up correctly you should use a non vented cap. If you don't have one either from the factory or has been removed and the hoses plugged you must use a vented cap.
Be sure you are using the molded fuel hose from the frame to the pump. Bulk hose often crimps.
Mike
Also check for the vapor cannister. If you have one and it is hooked up correctly you should use a non vented cap. If you don't have one either from the factory or has been removed and the hoses plugged you must use a vented cap.
Be sure you are using the molded fuel hose from the frame to the pump. Bulk hose often crimps.
Mike
Advanced
Joined: Aug 2006
Posts: 72
Likes: 0
Man I love this forum! My 78 is doing the same thing, so thanks for posting and for all the suggestions. Mine starts, runs, idles and drives fine in town, but ask it to do more than that or take off from a dead stop with gusto and it sputters like a moped. I've yet to get it over 70, and man, it's a Corvette! I wanna GO!!
