fuel delivery issues

[jctucker]

***update***

Replaced a few frayed fuel lines. Cranked, still doesn't start. I pressurized the gas tank with everything hooked up. Ignition! Fired right up. Ran great. Shut it off and it started right up again. Weird.

Thanks a ton for everyone's help!!

[bulldog4444]

Great news! I still would consider the inline electronic pump as a backup. Also, remember to replace all your hoses with fuel injection hose. All the fuel hoses.

I'm sure you're smiling now!

Good luck,

Bull

[jctucker]

Yeah, I replaced the hoses with high pressure lines even though it's a carb car.

Oh, and it did it again. Got it started Thursday night. Started RIGHT up Friday morning. Ran awesome Friday and drove it home from work. It sat on my steep driveway until Sunday afternoon when I went to go get beer- started right up again and ran well (though it has a hard time staying idling when cold, which is new). Parked it again on the hill and sat until Tuesday morning when I went to leave for work. Nothing. Cranks, no start. No fuel again.

At this point I'm suspecting I've got some kind of crack in the fuel delivery line that goes into the body and comes out in the firewall. Unless there's some crap floating around, but everything looks really clean. I'm probably going to install a back up electric pump to re-pressurize the system when this happens. Very, very frustrating.

*First thing I'm going to try this time is running a hose into a 5 gallon container of gas right off the mechanical fuel pump inlet and see if that works. I've tried the 'cracking the fuel filler cap' idea, no dice.

[seabeelt]

Sounds like you have just enough of an air leak in the fuel line to facilitate lack of a good vaccum pull from the fuel pump and allowing air to seep back into the line when you park the car in your "steep" drive while having gravity pull the fuel back to the tank. I'm beginning to think that this is more and more a fuel line/supply issue and has little to actually do with the pump. Also check above the rear axel, there is sometimes a small check valve located there that could be malfunctioning. It can be removed without much consequence. Hope that helps
r/

[jctucker]

Yeah, that's been my conclusion the last day as well. It's weird there's no fuel leaking out, but gas does evaporate really quickly. I'll take a good look for that check valve. At this point I'm probably going to run a brand new stainless fuel line along the body channel and up to the engine compartment.

Thought: could I install a check valve up near the mechanical pump to avoid having fuel seep back into the tank? VW and Audi electric in-tank fuel pumps have a check valve that prevents this from happening to quicken cranking times when the car has sat for several hours.

[majicwrench]

The mechanical pump has a checkvalve in it to prevent fuel from draining back.
Keith

[So Cal Mark]

I believe 79 was the first year they ran the hard fuel line inside the car. They tend to rust where they are clamped to the floor. Seepage there is soaked up by the insulation.

[jctucker]

Keith- Ok, thanks. So that won't help. =)

Mark- That totally makes sense. I'll pull the carpet up tonight and check. Already got an 8' 5/16ths line on the way for this evening. Again, thanks so much for your help.

[majicwrench]

I didn't say it wouldn't help.
The check vavle in the mechanical pump can get debris stuck under it which renders it ineffective. I'm really fond of testing things. Cap the fuel line back at the tank, hook your vacuum pump up at the pump and see if you can create and hold a vacuum in the line from the pump to the tank.
Keith

[jctucker]

Keith- Did that during the first round of testing. There's a leak between the pump and the tank for sure. i've traced it down to somewhere where the hardline enters the body and where it exits from the firewall. My new line showed up yesterday evening at work, so I'll try to get it knocked out saturday and let you guys know.

[124JOE]

hello


just for giggles grab and pull your pos and neg cables and tug a few


hope this helps

[jctucker]

I removed the old fuel line and got the new one installed. Engine fired right off after just a second or so of cranking (pretty good considering there wasn't any fuel in the line). I got some cool 5/16" outside diameter aluminum brake line to use. Worked pretty well! We'll see after driving it down to less than 3/4 of tank how it does.