I’ve had issues with my tank for years.... I can never fill it up all the way, if I do (I suspect) a bunch of grime in the tank somehow makes it to the sock on the sending unit and clogs it up... it takes a couple days of driving for it to clear up. In the past I’ve pulled the fuel filter at the carb to check and it looks clean on the inside and out...so the problem isn’t there. Also, a full tank of gas maxes out the fuel guage.... puts it at 3 o’clock on the cluster and it stays there until I’m close to half.... so I figure the sending unit is also catching, possibly something on the float, or maybe the ground is compromised. Anyway, my work around has been never to fill it more than half...and as long as I don’t forget, I’m fine.....well, I forgot again lol So, tanks are cheap and so are sending units and it’s a pretty straight fwd job... I figured I would just take care of it but was wondering if I should just try to clean up the old tank and reuse it? Any pros or cons? thanks
What I would do is drop the tank (which your going to do anyway) remove the sending unit, and have a looky see inside. If all is clean, which I bet it is, replace just the sending unit if its not working properly. I've never seen a gas tank with garbage in it IF the car is driven, even on a semi regular basis, unless someone put crap in the tank, same goes for fuel filters. First time I dropped the tank in my GS was back in '94 when I redid the whole car, it was spotless, fast forward to 2017, I dropped it again to install Robb Mc's 1/2" pick up, and again, it was spotless.
Yea, I guess it doesn’t hurt to look first. If I drop it I will for sure replace the gas lines back there.... there are 3 rubber connectors I believe.... am I correct that two are half inch and one is 5/16? These are the connectors that connect to the steel lines.
I dont remember on the sizes out of the sending unit, but dont forget theres two more, one on each side of the tank, at least there is on my '71 W/AC
Yea, I think those are for venting right? Since the cap is ventless.... I think one goes to the smog canister. I’ve ran across a diagram on here before I’ll have to search it out again. Thanks
Yeah...new ones are cheap and they look a hell of a lot better, too. You'll already be over $100 into having the old one cleaned anyway. New tanks from Spectra come with necks, so you shouldn't need to save the old one. Even the 70 tanks have necks now. I've bought 4 in the last 2 years. The only issue I had with the last 70 I bought, was that the cap ring was clocked wrong...purely cosmetic. Of course I had to reclock it because it was annoying.
Just replaced my 70 tank this season. Was getting ready for a track day and found a leak. Ordered a Spectra from Summit Racing, came with neck..JIM
I'll go against the grain here.. I'd diagnose the issue before loading the parts cannon. I wonder if you have a venting issue? Also i'm becoming cheap in my old age. I'd rather spend an hour or two cleaning something before spending the money to replace it..
ive done a few tanks myself with just apple cider and ball bearings. pretty much free. not saying i wouldnt buy new my buicks just saying on a flip car its alot cheaper to clean them.
When you swap the hoses pay the $5 a foot for fuel injection grade rubber hose for the 2 main hoses, it holds up far better. ( you can use the cheaper stuff for the vents). Sadly, all the new hose fails in years vs the old stuff that will go for decades. Gates makes a higher grade non-injection grade hose with green print (I think it's vapor resistant rated) that's also pretty decent. My wildcat tank isn't made so I took it down last fall to get it coated and to paint it. I was stunned how clean it was inside. I think it's worth a look because it seems like the newer stuff is always cheaper somewhere... if it's a mess inside, pitch it, if not, I would resolve the root cause and keep it.
Joe, any suggestions on how to diagnose a venting issue? Run it without a gas cap or pull one of the vent hoses and run it? Since this is a full throttle scenario... I don’t think having the cap off would be ideal lol. The issue only happens at full throttle and it hesitates like it’s fuel starved.... mind you, this has only happened to me 3 times ever and it is always after a full tank fill up. ...it usually subsides after 4 or 5 rides. Maybe gunk is getting into the vents and not the sock. Thanks for the help
Why not try blowing air through the vents, into the tank? That's easy to do. If it won't go in...it can't come out... :_) I would start by looking for mud bees at the ends of the vent hoses.
I bought some of this stuff about 8 years back when I redid all the fuel hoses under the hood and had no idea it was expensive. I was a bit shocked when I paid for it......it still looks good though.
X2 on that! I'm the same way lol. Your tank may not even be the source of the problem. Most gas tanks (80%-90%) can be cleaned and coated on the inside, much cheaper than buying a new one. I have cleaned and coated a few tanks over the years, works great. Keith
just replace the gas tank and sending unit, done with problem, did it a couple of yrs. ago no more issues with fuel gauge nor gas tank . problem solved. AL
