I have a 72 Supreme w/ a 350. She's sat for a long time but I got her running. I have a general automotive question. It starts and idles nicely. It just doesn't have the "go-go" I would expect? Even for an old girl like her. I noticed that the glass fuel filter seems to fill and empty as the engine is running. It also seem to have alot of bubbles in the fuel? Shouldn't there be a constant flow of fuel? Could shellack be the problem?

Thanks for the help.

 

Could be a couple of things.

1. pin hole in the gas line to the tank of rubber line from the fuel pump to the
carb and sucking a little air but the hole is not enough to leak gas

2. Fuel pump Diaphragm is wearing out (need a new fuel pump

3. Fuel tank pick up screen clogged due to rust and crap in the tank

4. Fuel filter clogged

start with the fuel filter, fuel lines, fuel pump, save the fuel tank pick up screen for last

Check all of the above

 

Thanks for the reply. That will give me a few things to do this weekend. I have a new carb on it. As far as the fuel filter, do you mean the filter at the carb? There's no filter before the fuel pump......or is there? I pulled the rubber line off the inlet side of the pump. I was expecting to have at least some fuel leak out of the line from the tank. No (little) fuel ran out. Could that mean a fuel line block from the tank?

Jim

Jim

 

citcapp was referring to the sock filter that is on the fuel pickup inside the tank. when these things sit with old fuel it can varnish up and plug the sock. if there was no fuel in the line at the pump there is a good chance that it is the sock or as said maybe a pinhole in the steel fuel line or a rubber line.

 

What he said. I ended up having to do all of the above, plus flushing out the tank, on my 62 recently.

 

Whatever you call the stuff "shellack" or varnish, it sounds like I got a bad case of it! I wonder if it would be easier to replace the tank? Don't I have to remove the tank to get to the pickup? Should I also go ahead and replace the sending unit? Thanks to all.

Jim

 

I recently (should be fix tomorrow) had the same problem. My SX with a rebuilt carb was cutting off when accelerating or coaster even at variable speeds. The tank had some rust and moisture and needed to be re-lined. This also caused all the fuel filters to get clogged and replaced. Car should be fixed tomorrow :-)

 

Yes.
Only if the sending unit is bad.

Check steel fuel lines for rust, corrosion, or 'wet' spots.
If the old rubber hoses from the tank to the fuel pump look old, then replace them first. Same with the ones from the tank to the vapor separator. If they look very old or cracked or rotted, this needs to be done anyway for safety, whether they may fix your problem or not.

A very old fuel pump should be replaced out of prevention anyways.
I have seen an old one an Olds 307 rupture internally and pump fuel into the crankcase before.

Only as the last step would I drop the tank.

 

I replaced the tank and sending unit today on my 68 442. The sending unit was bad and the tank was quite rusty. About the sending unit, we only knew that the gauge didn't work not that the filter bag was 3/4 gone. Now the car runs like a top. Not a bad job to do btw just takes a little time.

 

pull the fuel line at the pump, remove the gas cap and blow air back into the tank, not a lot of pressure 120 psi not so good, but itl clean the sock

 

A good tip to get one home or buy a number of days until the tank can be removed. 20psi would suffice.
Unfortunately, all that junk blown off the sock will be eventually get sucked up again, allowing you to become stranded in possibly a worse place at a worse time...