Fuel Problems SOLVED
 

I have had a starving carburetor for months.

I drive a 1980 GS that is pretty much stock. A few months after I bought it, the car showed a particular problem that only occurred only on steep hills or under heavy acceleration. After about 20 seconds going uphill, or after about 3rd gear when flooring it from a stop, the carb would starve out, sputter, stop accelerating, start, stop, on and off as if I were tapdancing on the gas pedal. I could take it easy for a few seconds and continue just fine, and it seemed like the bowls were simply running dry.

I searched the forum up and down looking for people with similar problems, and I came to the conclusion that I had a faulty fuel pump. I learned that the factory fuel pump had a short lifespan and could cause this problem. I bought a new fuel pump and put it in, along with a new fuel filter. It worked fine, but it didn't fix the problem.

I don't know a lot about carburetors, and it seemed like a rebuild wouldn't fix any of the fuel metering components, so my dad and I focused on the parts that the fuel goes through before it hits the carburetor. Specifically, dad worried that the fuel lines and fuel tank were old and clogged. I read stories about people whose fuel lines had gummed up with corroded rubber and gasoline, and people whose fuel tanks were clogged with dirt and rust.

We did the fuel volume test as outlined in the Haynes manual. Only 14 oz. of fuel was getting to the carb every minute. That's 1/4 of what it should be getting. Since the fuel pump was new, and running strong by the sound of it, I figured it must be the lines or the tank. In the diagrams, dad found that there is a small strainer in the fuel tank itself, a kind of pre-filter before the fuel exits the tank on its way to the real filter and fuel pump.

So one weekend while I was away from home, he took the gas cap off, removed the line going into the fuel filter, put his lips to it, and blew as hard as he could. He said he could hear bubbles coming from the fuel tank. After putting the hose back in its place, he did the fuel volume test again, and got well above the minimum flow number (I forgot how much it is, like 33oz or something).

He figured that the air he blew blasted the dirt off of the strainer in the fuel tank, allowing it to flow much better. The car drives fine now. I reccomend this to anyone who has fuel problems, because our gas tanks and fuel lines are over 20 years old and probably not in the best shape.

Great tip!

I wonder if it would be a good idea to do that at the time the fuel filter is changed, as a maintanance procedure.

Thanks!

Myc1972

I may do this except with compressed air, good tip.

Keep the air pressure low, and drain the tank afterwards, or it will plug again.

I had a similiar problem, only the screen was split and the pick up tube was full of rust. Sure glad I have a bead blast cabinet.

I wonder how much it work it would take to fix the problem for good.

Or I wonder how much money it would cost to have someone do it.

Don't be a silly priss. Just do it with your dad. Drain the tank, drop it, flush it out and check the fuel pick up. While it's out, replace the fuel lines and possibly the fuel pick up screen.

Hi Joe-
Problem solved? Maybe. Maybe not. One of my 1980 RX7's exhibits the same problem as yours at about the 1/3rd level of fuel in the tank. Coughs and dies. I'm pretty sure the tank is rusted internally. It needs to be removed to be repaired. Its actually not too hard to remove, being held in place by 2 straps, once the 3 fuel hoses and the filler hose are detached... and the harness for the sender detached on the driver's side of the tank. The real B!tch is getting the tank drained first because Mazda in their wisedom did NOT put a drain plug in our year of RX7... so siphoning seems to be the answer. Even then some fuel will remain and it makes handling the tank a definite 2-man job to lower from the car
I am using the POR-15 US tank sealer kit ( POR-15.com). They have excellent products. It involves cleaning out the gunk (by mechanically sloshing it around... the "mechanical" part would be you doing the sloshing) with a special solvent/cleaner, then pouring in a special sealer and likewise sloshing, etc. I believe the POR site details this.
With the tank out it might be a good time to check back up in that rear area to clean out and rust protect the area around the tank too. POR has some great rust protection/elimination stuff for that too.
Good luck to both of us :)
Stu Aull
80GS Alaska