Biobor is a "pesticide" of sorts - it kills fungi dead dead dead. It is best used as a preventative on a routine basis. It is _only_ for diesel or jet fuel, or other kerosine-like fuels. There are many other similar diesel fuel treatments to prevent growth in the tanks.
Fungal growth will NOT appear in gasoline.
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I was in error in not pointing out earlier that it is a fungal growth, not a bacterial growth, that causes the problem.
My guess would be a bad ground tag or a bad/dirty ballast resistor if you have one.
Some have a ceramic ballast resistor on the power side of the circuit to cut the voltage down to the pump to make the pump sound quieter. The two wires going to it can just be hooked together to bypass it. On mine it is way out near the rad on the drivers side fender.
If the pump has a bad ground tag, it can draw too many amps and wear out fast or only be able to draw enough to jump a bad connection when brand new.
On some XJ's the main computer ground tags are on the firewall inside just above the gas pedal, some are on the engine block maybe on the back passenger side and the main ground is a mesh cable from the engine head to the firewall.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Running near empty causes a lot of air to enter the pump, seriously shortening it's life. I don't like to let a fuel injected vehicle get below a quarter tank .
Other causes might include a defective pressure regulator or leaks between the pump and the tank outlet.
You raise a good question here. Like I say, measure the length of the internal pump and how far it sits off the low spot in the tank. To be completely submerged you need AT LEAST 5-6 inches for the length of the pump plus the inlet (which is plastic) and the sock pressed onto it. As for your hotrods, do you know if they use a pressure regulator that will allow constant flow thru the pump? I ran capacity checks on mine and if at least 80% of the pump capacity wasn't being recirculated I couldn't make to the next gas station without running out of gas - sucker filled the 3 liter bottle in nothing flat at idle. That was just running the return line into the bottle - downstream of the regulator.
It is an in-tank electric pump. The mechanic inspected the tank and found nothing wrong. All the wiring was replaced the previous time they replaced the pump.
The guy is at a loss to explain it. He said that the pump actually spins, but nothing flows out. At least he is honest to admit that he is clueless, rather than saddle me with bogus repairs. His best guess is that it's a bad batch of pumps.
The warranty is renewed for another year every time they replace the pump.
I purchased an aftermarket pump (Bosch) to have as a spare in case the new one craps out on me while I am in the boonies. Apparently, it is not hard to replace in the field. No need to drop the tank. The pump is mounted on the front side of the tank.
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