Fuel Tank Cleanout
I'm having my 3rd go-round with clogged injectors over the past 9 months.
My 1st mechanic suspects the car sat awhile before I got it. It was an '88 w/ 58k when I bought it last Jan, so at 5K per year maybe so.
Here's what happens. One or two injectors gets impacted with fine brown particles. It clogs them up completely. Seems to happen if I let the tank get below 1/4, surprise surprise. I can hear the fuel pump running more loudly during each one of these incidents, telling me it's working harder. Under most conditions, I don't hear it at all unless I really listen.
'88 5spd in beautiful shape otherwise
It sounds like you have some varnish build up in the system. I suspect that the red dust stuff you are seeing is not rust but just old accumulated gasoline. With very few miles per year it is possible that this varnish has accumulated in the system and some melts away from time to time clogging things up. Gas treatment can just knock some of this loose and create more trouble than it solves. Tracking down rust sources is much less likely since there are very few if any parts of the system that can rust.
The first place I would look is the gas tank - and no I do not think you will need a new one. There are two critical areas of the tank to check. First go to the auto parts store and buy yourself a couple of gallons of Berryman's and a gallon of Marvel Mystery Oil. Accept no substitutes. Get some beer while you are out - you will need it.
1. Drain all of the gas in the tank and plug the gas line.
2. Remove the fuel gauge unit from tank and put it aside.
3. Pour a half gallon of the Berryman's into the bottom of the tank and let the car sit for a couple of days. Make sure that Berryman's has not evaporated and add more if needed.
4. Drain the Berryman's observe the color - I will bet that it will not be clear.
5. Very carefully use box or socket wrench to remove the tank filter screen. Be careful not to damage the tank by twisting out the treaded bushing that holds the screen. If it will not come free - soak a while longer and squirt some on the outside as well.
6. With the screen and sending unit out access to the tank is easy. There is a baffle at the bottom of the tank that acts as a reserve and prevents the pump from going dry on sharp turns with a low gas tank. The baffle can be separated and cleaned but if you used enough Berryman's it should already be clean. Soak a rag in Berryman's and attach it to a rod and use it to swish around inside of the tank. You will likely see lumps of brown stuff. These are deposits of dried old gas and can be wiped up with the soaked rag.
7. Once the tank is clean you can rinse it out with a little gas to get out all of the fibers that could be left from the rag.
8. Next inspect the sending units. The most common place for accumulation of junk is the return tube. You might find that it has a heavy coating of varnish. The unit, if you are careful, comes apart and can be cleaned - again with Berryman's. Soaking and scrubbing is the best bet.
9. I would also inspect all of the gas lines at this point and replace any rubber hoses that are old. The one running from the fuel pump under the tank is a candidate for replacement.
I find that it is easier to do this with the tank off. It is not that big a job to remove it and it goes back on easier than it comes off. I would also check the vapor return system to make sure that you are not getting any debris from that - but my best guess is old gas varnish accumulated in the system. Once everything is clean I would again get a new filter, flush the fuel pump with Berryman's and replace the tank screen. DO NOT IGNORE REPLACING THE FUEL SCREEN - it can fragment and take out the fuel pump.
Also be careful, Berryman's can explode just like Gasoline - work in a well ventilated place with no open flame and keep the rags in a can or outside. I use shop towels with a treatment and just put them in a pail of water when I am done and then dry them out again later to reuse.
If you do remove the tank be sure that all of the rubber pads are in place to prevent chaffing and cracks later on down the line.
Remember a clean fuel system is critical with a Fuel Injected car.
After the car is running again - fill the tank and add a pint of Berryman's (they make a special gas treatment - but I think it is the same stuff). Run the tank down to a quarter or so and refill it. This time add a pint of Marvel Mystery oil. This will both clean and lubricate your fuel system. The Mystery Oil will quiet down both your injectors and the fuel pump. It also is good for the upper end of you engine. Add a pint to the crank case with each oil change as well. Add a pint to the gas every six months of 5000 miles.
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