Rusty Tank Expierence

[Jim Fierst]

About 9 months ago I first notice a fuel starvation problem on the (carbed) 79 LBZ under hard acceleration. I checked the rear (before the pump) filter and found rust. I replaced the filter as a temporary fix. I found a replacement tank and debated on a DIY coating job but opted to have a local shop with a good reputation do it. I got by for a while draining the entry side of the rear filter but finally had to install the tank when the engine started running rough. It is really a 2 man job doing the R & R. Along the way I changed all the rubber hoses . I changed both the front and rear filters but enough of the rust had gotten through that I had to blow out all the jets and carb passages including the idle circuit.
Everything seems fine but I will drop the entry hose to the rear filter sometime soon to make sure the new tank has no problems.

[FinnJohn]

I'm wrestling this particular alligator too ... there's a sort of cup in the bottom of the fuel tank that seems to be there to make sure there's fuel to be picked up when you're holding a tight turn with a quarter tank of fuel, so that when all the fuel sloshes off to the side of the tank there's still something to pick up. It seems mine is buggered up and won't let fuel in. So, she runs great on half a tank or better (fuel fills the cup from the top) and chokes out when there's less. I guess I'll have to have the tank boiled out eventually, but for now I'm just keeping the tank topped off. I hate working on cars in bad weather. High humidity, numb fingers, etc. (I don't have a closed/heated garage, just a carport.)

Cheers!

--Finn

[Jim Fierst]

What I probably should have said in the original post is plan on cleaning everything in the fuel system especially if the vehicle is carbed.

[Will]

I mentioned this in another post, but maybe it should be a sticky:

I've been doing some research on a similar bad-fuel issue on my boat, unfortunately a below-floor tank that is not removable. Here's a brief synopsis of what I learned:

As part of the Energy Bill of 2005, MTBE was phased out as being a possible carcinogen, and the law was changed so that oxygenated (read: MTBE laced) fuels were to be discontinued in favor of ethanol blended fuels. In some places, like Minnesota, this was to be a high percentage of Ethanol (E85, or 85% Ethanol) but most places were to be 10% Ethanol, or E10. What you most likely have in your tank today is E10. You may note a placard on the pump at the filling station that says this.

OK, so why is this important? Because E10 undergoes a different kind of breakdown than straight gasoline. Ethanol is hygroscopic, it bonds to water. It has a slightly different specific gravity than gasoline. In normal use, your car bounces around and the ethanol remains in more or less a colloidal suspension with occasional agitation. But when the car then sits for a period of time (or a boat on blocks) the fuel undergoes a change called "phase separation".

OK, why is this important? Because what you end up with is a layer of water-laden ethanol at the bottom of the tank (where the pickup is), a layer of fuel, and a top layer of very low-octane fuel. To compound things, bacteria grows at the fuel-water interface and hastens decomposition of the fuel.

Experts say that stabilizer is of very limited use to prevent this. At one time, as many of us were taught, it was thought topping off the tank was THE way to winterize. However, unless you plan on jumping up and down on the bumper daily to agitate your tank, it would probably be more advisable to dope the tank with stabilizer but then burn the tank as empty as possible before winter storage. Since you are now burning an aqueous fuel blend, an oil change is probably also adviable and a top cylinder lubricant is mandatory, at least in my book- I use Marvel Mystery Oil, about 1TSP per plug hole, followed by pulling the coil wire and cranking for about 5 seconds.I know there are specialized dessicant dummy spark plugs but I've not used any to date.

Hope this gives some of us pause who have been previously in the habit of dumping in some Sta-bil and filling the tank. Everything I've read from the experts says the lifespan of E10 is measured in weeks, not months.

[Tonyj]

Might not be the 'bowl/cup' that's wrong. Could be a crack/hole in your feed pipe or pick up. When the fuel level drops and exposes the the feed pipe or top part of the pick up then air is sucked in causing fuel starvation.

[Jim Keller]

Good point Tony, the pickup tube can get rust holes in it