desertdatsuns.net

Thought I'd pass on something I learned after finally diagnosing and fixing my 240Z. I had drained about 2 1/2 gallons of bad gas out of another vehicle and put a little in each of three cars, including my 240, to dispose/burn it. A while later the car became difficult to start, if at all. It acted like something electrical, but after a month of trying to track down the issue, I did a compression test and discovered that cylinders 3 and 4 had no compression. At first, I feared I had a blown head gasket and would need to pull the head, but after conducting a second test I found compression had come up a little to 30 and 60lbs. After that I was able to start the car, though it didn't run well. The light finally went on while talking to Datsun Don, who suggested I may have stuck valves, due to the bad gas. After dumping a can of SeaFoam in the tank and driving the car 25 miles it seemed to be running much better. Another compression test showed 170 pounds in #1, 160 pounds in #2, #3, #4, and #5, and 165 pounds in #6. The car is back to running flawlessly again. Don said in his experience a gallon of bad gas will tend to contaminate a full tank of good gas, rather than the good gas diluting a gallon of bad gas. Painful lesson learned. I'm now a SeaFoam believer and will likely throw a can in all my cars periodically just to keep the engine clean.

On my my dirt bikes I used to regularly get the tiny pilot jet of the carb plugged solid with varnish if they sat for more than a month. This started when they started with the oxygenated fuels.

I started adding Sta-bil to the fuel and have not had that problem in many years. Generally my cars don't sit that long, but If I had one that did I would use Sta-bil in that also.