Good morning from Florida! I'm taking care of a 1979 Corvette, L48, recently rebuilt Quadrajet, automatic -TH350. I'm fixing to dive into the threads and do some research but thought I'd post my situation to say hello...
Recently I was driving on the highway and the car died, as if it ran out of gas but it had/has about 1/2 tank. Motor would turn but not crank, will crank with starter fluid at the carb but immediately dies.
I replaced the fuel pump less than a year ago and it's been fine since, I didn't drive it from July thru December much. I noticed the rubber fuel "S" feed line to the pump was kinked to the point that I don't know how it even started in the first place.
Got it home and replaced the feed line, fuel did leak out of line from tank and the port to the pump when I removed the line.
Everything looks good, no leaks, but still won't start.
Just wading into the forum hoping for suggestions, thanks in advance.

 

Welcome to The Corvette Forum Dirt's79!

This THE place to be if you have questions or issues with a Corvette!

I am by no means an expert on the 1975 Corvette but there are certain things that carry over from earlier Corvettes. Did you check for a spark when the car would not start?

Once before going on a long ride I noticed a tiny puddle forming on the ground underneath my 1968 C3. It turned out to be a tiny pin ***** of a hole in the copper fuel supply tube and it was spraying out the tiniest mist of gasoline that would almost evaporate before hitting the ground. That tiny hole was on the vacuum side of the fuel pump and knowing that I would be pulling air into the fuel system and this causes problems similar to yours.

I would have probably filled the bowls through the vent tubes on the top of many carburetors and then see if it started and ran normally.

Rubber lines that handle fuel are very susceptible to the ethanol in our gasoline. The parts inside the carburetor need to be updated to a newer rubber than can resist ethanol as well. I would verify that the fuel is getting through the lines easily. On our 1988 C4 we parked it for the winter and by the next spring the fuel supply line was almost rusted shut Internally. (thank you Ethanol)!! It would supply the needed pressure and the there gas was at the engine so we thought it was okay. It turned out that the fuel line was not flowing enough Fuel and it would shut down for an hour or so. I bypassed the fuel supply line with an external hose and the problem went away. I had "pressure" and "gasoline" but nowhere the VOLUME of fuel needed for it to run. This was a bit of a challenge to figure out. There was also corrosion that caused a low voltage situation which aggravated the problem.

Your 1975 C3 has a lot more emissions equipment on it than I am familiar with. Do you have a vented gas cap or not? A non-venting gas cap on an earlier C3 would cause it to shut down randomly, or a car with a non-vented cap might have issues with other emissions equipment blocking the air flow that replaces the gasoline as it is used. When you open the gas cap does it release pressure or anything?

Something is keeping your gasoline from getting to the right parts and that needs to be checked out. If the "sock" in the fuel tank gets dirty it could also be contributing to the problem. To clean that out temporarily I simply blow back into the fuel tank releasing the contaminants from blocking the fuel supply. Even a really dirty fuel filter could cause the shut-downs.

Keep us posted on what you find please. This is how we ALL learn here at the Corvette Forum!

 

Run pressure and flow test while cranking would be good.
Close up inspection of fuel lines for leaks or patches as i had an issue with rusted lines letting air in.
tank sock?

i went through a few things here finally fixng on my 79
https://www.corvetteforum.com/forums...e-on-road.html

 

Thanks much for the quick replies, still researching, I'll reply better when I know more and have more time.

 

My first clue is your statement that the preformed "S" hose was kinked.
I have never seen a preformed do that.
But quite common when someone tries to save some money and fabricate a "S" hose.

So, I assume you installed a factory "S" hose?

Any time fuel supply is in question, such as your cranking & cranking, simply take some lawnmower gas in a plastic water bottle and dribble a little into the carb.
If it starts, you have a supply issue.

 

Wow - amazing : people are actually giving good practical advise - ALL of them

#1 - pour a bit of gas through the carb -doesn't really matter where as long as you pour some in both left and right "barrels" - see if it starts and runs a couple of spins of crank - confirms fuel deliver problem
#2 - find small funnel & fuel line (5/16" ?) install fuel line & funnel over float bowl vent tube pour gas in using a small cup until fuel spurts out of top of carb - start engine again - should run for a minute or so -
#3 - now pull rubber hose off fuel pump and find length of 3/8" hose to put on pump inlet long enough to submerge other end in a small jar or jug of gas.
Restart engine using either steps above so that it runs long enough to start sucking gas out of gas container and continues to run. If it runs fine now you know your pump and plumbing to carb are okay.
#4- start as per previous posts looking for porosity / rusted through fuel line , plugged sock etc.
On my 1980's GM carburated cars - it was very common for the fuel lines exiting the fuel tank to rust through on the bend coming out of the sender flange.
There used to be aftermarket kits to break off rotted fuel line and insert rust repair line into old line and resolder.
Good luck !

 

Thanks again to everyone for the quick replies, you folks are great-
I have new info, I disconnected the line from the carb, put it into a jug and tried to crank it- not a drop of fuel in the jug.
I just replaced the fuel pump in January of last year, if I remember correctly the pump is a Carquest brand pump, not to bash but for clarification. Also, as far as i can tell there is no fuel in the oil, oil on the dipstick looks ok.
To confirm, the old S feed line that was kinked was just fuel line that had been sort of manipulated into somewhat of an S shape, hence the kink.
I did replace it with the preformed S feed line, which is now quite... kinkless.
Again, thanks much for your suggestions.

 

Just curious.
The Carquest pump is a three port unit?
Inlet, from tank.
Outlet to return
Outlet to carb

 

Good morning, correct, it is a 3 port unit.

 

Bad pump. You need another new one. The new ones are notorious for going bad in no time at all. Also check the pressure after you replace it. Remotely possible the pushrod is bad but more likely the pump.

 

Thanks for all the suggestions everybody.
I haven't had time to get back to work on the car, I hope to get into it this weekend.

 

With millions of SBC still out there, you would think somebody would still manufacture a unit that will last as long as the original.
The new units are hit-n-miss whether they have any longevity.
Some of the issues were a broken spring on the arm, the arms hinge pin failure and diaphragm failures.

Lots of SBC pumps on the market by good reputable companies. However, searching / buying a three-port unit really limits the options.

If you do elect to remove your pump, with the front end up on ramps, you will have less fuel from tank supply line trying to escape.
Stopping the crankshaft at TDC #1 moves the pumps pushrod farthest away from the pump arm.
You can remove a short bolt at the front of the block and replace with a longer bolt temporarily. The longer bolt will help you hold the pushrod up.
Obviously, don't forget to swap the bolt back.

If you suspect the pumps mounting plate gasket is weeping oil, great time to swap that gasket as well.
The pumps two mounting bolts can be accessed with a 3/8" drive w/ long extension from underneath. No need to remove Rt front tire.

 

Thanks much for all the replies and suggestions - the fuel pump was, in fact, shot.
I'm really disappointed that the Carquest pump didn't even last a year... lesson learned though, I guess.

Due mostly to my not being able to easily get the car to a level bit of earth to jack it up and get the wheel off, it required the better part of a day and countless obscenities.
All seems to be well now, after addressing a few leaks as a result of also replacing that S feed line and the hard line from the pump to the carb.

Despite the hassle, what a glorious car.
In my opinion, the C3 design is one of man's most beautiful creations.