Dear Tom and Ray:

I have been working on a feed truck for some time. The gas is getting into the oil pan. I put on a new carburetor and that didn't stop it. I put on a new fuel pump and that didn't stop it. I put on another new fuel pump and that still didn't stop it. Can you help me? -- Ted

Tom: A feed truck? That's one of those little catering trucks that sells donuts and coffee at construction sites, right? We call them "roach coaches."

Ray: I think he's talking about a farm vehicle. Anyway, Ted, here's what I'd check. I'd start by making sure the thermostat is closing.

Tom: Right. If the thermostat is always open, the engine will never reach proper operating temperature. And at less-than-proper-operating temperature, the fuel doesn't combust completely, and the leftover fuel would find its way past the rings and into the oil pan.

Ray: Another possibility is that your choke is never opening up. That would cause the carburetor to continually pour way too much gasoline into the cylinders, with the same result.

Tom: And one other possibility is that the carburetor you put in is no good. You say you replaced the carburetor, but you didn't say with what. Did you put in a new carburetor? A rebuilt carburetor? Or just the carburetor from your neighbor's feed truck? Carburetors are touchy. So if all else fails, you might want to try swapping another carburetor in there and seeing if that fixes it. Good luck, Ted

Don't get stuck with a lemon. Be an informed shopper. Read Tom and Ray's guide "How to Buy a Great Used Car: Secrets Only Your Mechanic Knows." To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1998 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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