We have an 02 GMC 6.6L here at work, and this morning the truck died and refused to restart after warming up for 15 minutes.

I checked the fuel, and drained the filter. What came out of the filter was a yellow liquid that I have not been able to identify. I first thought that someone had accidentally filled up the tank with gasoline, as the truck was filled up with fuel on Friday. However, after pumping some fuel out of the tank, it came out the normal green diesel. I pumped up the filter several times, and kept getting the yellow liquid.

I finally decided to replace the filter. Truck fired up and has been running normal since. I'm a bit stumped at what actually came out of the filter. Here's a picture of the fuel in question:



I drained at least 6 cups of fuel out of the filter, and they all looked that.

The general manager said he's been using a Lucas fuel additive. I've yet had a chance to examine this additive to make sure it's compatible with diesel fuel.

Anyone else ever experienced anything like this?

Casey