Car won't swallow?

[tlorber]

Zed head, his car only takes 7-8 gallons from empty to full, so irrespective of what the gauge reads, he is only able to get that much in the tank. Definitely a strange phenomenon. Is there any chance there is something in the tank preventing it from filling completely? As stated above, maybe it's time to drop the tank and find out what the deuce is going on there. If you do that, you should replace all the vent hoses-all 27 different sizes of them.

[ajmcforester]

When was the last time the tank was cleaned out, and boiled for rust? I'm wondering if rust and/or sediment is blocking 1/2 the tank at the baffle. does the gas level at the fill tube go down when it sits?

[Zed Head]

Here's the link to that story about the vent line. It was just a couple of weeks ago, by Bruce Palmer - http://www.classiczcars.com/forums/showthread.php?42008-fuel-system-closed - Post #7.

tlorber, 5th didn't actually say his tank would only take 7-8 gallons (unless I misunderstood his description). He said it only took 7 (6) after the gauge showed E.

Any news?

[5thhorsemann]

This one has me stumped, I took a 2 gallon can with me in the hatch, and ran the car out of gas for a second time. pulled the drain plug on the bottom and confirmed it to be empty. Then I put the 2 gallons in and drove to the gas station and it took 5.3 gallons. I could actually see the gas in the neck and the gauge read 1/2 tank. I then ran the car around the block (approx. 6 miles) and back to the pump. It took 2.6 gallons and again I can see fuel in the neck, the gauge now reads between 1/2 and 3/4. So the sender is not hitting the top of the tank.

The tank seems to be the correct shape, I didn't drop it but did poke around the top with a coat hanger bent into an "L" shape and couldn't find a depression to turn the "L" down into. So I'm relatively sure it is not crushed.

I ran all the vent lines to the evap tank, no kinks or "s" traps. When I pop the fill cap I get no pressure or vaccume sounds. I checked both fuel filters and they are spotless, even after the tank was run completely dry twice. So, By process of elimination I feel that it is in the evap tank. I pulled all the hoses and blew 5 pounds of air through the hoses and the tank itself, no restrictions anywhere.

Went to the gas station and with the gauge reading just over half, it took 2.1 gallons, could see fuel in the neck, and the gauge now reads almost 3/4 tank. I am POSITIVE it is not the gauge or sender. The tank must be getting air bound in the venting, or hydrolocked at the baffle.

I have not been able to find a baffle configuration diagram in my FSM or on the web. Anyone ever cut a tank up to see what the baffle looks like?

The car runs fine, but she just won't swallow.

[5thhorsemann]

Sorry for stealing a pic from another thread, but using it as a visual tool, I varified that I have checked all the vent lines and they are all clear. I'm back to the tank baffel.

[Patcon]

Looking at your picture the vent line from the top rear of the tank in the highest section of the tank. Take it loose from the vapor tank and see if you tank will take fuel then, provided that line is clear. That one line is responsible for allowing the use of the upper portion of the tank. If that line is crimped over or pinched the tank won't take fuel. I believe when you drive around the tank is belching air back into the filler neck and then it will take more fuel. If the tank isn't collapsed I believe your problem is between that vent port and the vent line at the top of the filler neck. I believe there is a drain off the vent tank that connects to the filler neck just below the cap. That allows the air to escape the tank after fuel fills above the neck of the tank.

Charles

[ajmcforester]

The tank is not venting, it's very clear with post #16. If it was the baffle you would read full at 1/2 to 3/4 full. You are reading 1/2 full when you are at 1/2. Some reason the upper two vent hoses are not venting. Something is not releasing the gasses. On the filler neck is the vent for the vent tank, see if you can blow air into the vent tank, and you might get bubbles in the gas tank if it was venting and you have a large enough pump. Not to say you did this, but I've seen people tighten the straps too much and crush the vent tubes on the top of the tank, or pinched the hoses.

[Bonzi Lon]

I've had my 73 tank down & refurbished. Looking in from the filler hole you can see the sending unit float, then the baffle, which is about where the "L" bend is, about 6 inches tall, no holes in the metal but, places at the bottom for fuel to go from side to side. These might be plugged with sediment, varnish, rust particles? On the other side of the baffle is the pick up & return tubes, you can see where they enter over the baffle. I was able to view the bottom of them by using a mirror & LED flashlight, actually you can view everywhere inside once down and the sending unit out, but you have to drop the tank. Hope this helps, some.

Bonzi Lon

[5thhorsemann]

That helps, if it were a baffel issue I would run out of gas at a half tank. Thanks all for the info. It has to be a venting problem. Weather is nasty, I'll get back into it in a few days.

[Bonzi Lon]

I re-read the first paragraph of post 16 several times. To me it sounds like the float is not floating and you are getting less than 3mpg. (drove 6 miles, 2.6 gal.) Hmmm

I know you don't want to, but I really think it is time to drop the tank and see what is going on in there. I HAD to drop mine, was nervous at first, but it was easy.

Bonzi Lon

[5thhorsemann]

Problem found!!!!!

Apearently when I replumbed the vent lines last fall, I cut the inner lining of the top hose which created a flapper valve in the tank fitting. air can pass into the top of the tank but not out.

I pulled the hose at the tank end, saw the cut liner. removed the first 1 1/2 inches of hose, reattached and the problem is now solved. Drove to the gas station with just under 1/2 tank and she took almost 9 gallons, and reads FULL.

Thanks for all the help everyone, kept me from pulling the tank for no reason.

[tlorber]

Great to hear that you can now spend $65.00 filling your tank, like the rest of us.