Topic: Fuel pump?
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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Need some advice. Drove the 68 the furthest I've ever driven it one way, about 90 miles a couple of weekends ago, to a Vette show. On the way home, it started wanting to cut out on me, and didn't want to go over about 30 mph without coughing. It did cut out at a stop sign while still in drive. The weird thing is when it is in park, it feels like it revs fine, plenty of gas. I took the aftermarket inline fuel filter off today, and it's flowing fine. So other prevailing opinions are replace the fuel pump. Anybody think any different? What about the filters that lead to the carbs?
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Could be the pump, but it could also be the "sock" filter in the fuel tank...they have a tendency to clog up after driving, and over the years, they may clog up enough to need replacement.
Remember, too, that your Tri-Power is really only runnin on the center carb until you get on it...then the end carbs come on-line.
Sometimes you can determine if the sock is clogged by removing the fuel line at the pump, and blowing back thru the line to the tank...with the gas cap off, of course. If there seems to be a fair amount of resistance, then the sock is probably in need of replacement.
If it seems to be fairly clear, then you are most likely looking at a pump problem.
Another possibility is the coil...it can cause the same symptoms.
Remember, too, that your Tri-Power is really only runnin on the center carb until you get on it...then the end carbs come on-line.
Sometimes you can determine if the sock is clogged by removing the fuel line at the pump, and blowing back thru the line to the tank...with the gas cap off, of course. If there seems to be a fair amount of resistance, then the sock is probably in need of replacement.
If it seems to be fairly clear, then you are most likely looking at a pump problem.
Another possibility is the coil...it can cause the same symptoms.
Joel Adams
C3VR Lifetime Member #56 
My Link 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Another thought, but a bit out there. I have seen it several times.
The charcoal cannister may be not venting the tank. After driving several miles the fuel pulled from the tank creates a vacuum, which in turn restricts fuel being pulled from the tank. If this is the case, removing the gas cap cures the problem.
Not likely the problem, but could be.
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
That's definitely an idea...does the '68 Tri-Power have a vented cap?
I've seen that happen too...it happened on my '85...took me a while to figure it out, but the metal line from the tank to the canister was clogged up. When I would remove the cap, it would be under vacuum(in colder weather)...in hot weather, it became hard to start after driving, unless I took the cap off to vent the pressure.
Dang cars is gonna drive me NUTS!!! and I kinda like drivin...
I've seen that happen too...it happened on my '85...took me a while to figure it out, but the metal line from the tank to the canister was clogged up. When I would remove the cap, it would be under vacuum(in colder weather)...in hot weather, it became hard to start after driving, unless I took the cap off to vent the pressure.
Dang cars is gonna drive me NUTS!!! and I kinda like drivin...
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
I'm not certain of the fuel line arrangement on the '68, but any rubber fuel hose between the tank and carb should be checked for cracks, unless your certain they've been changed recently. I've seen them so bad after 30 yrs. that it's a wonder they passed fuel at all. It can act just like the fuel pump going bad.
Jimmy B.
Just can't wait to get on the road again. 
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My Brother-n-law had a similar problem. He took a long trip and the farther he drove the weaker the car got. Finally wouldn't hardly pull at all. Turned out to be a kinked fuel line, where it made the curve to go up to the fuel pump.
Beautiful job on the paint! I have a '77 that looks about like yours did. Did you paint it yourself? I'm contemplating trying it but haven't received a lot of encouraging feedback.
Thanks,
Larry
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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