You are here:

Classic/Antique Car Repair/Chevrolet C10 Deluxe 1985


Fuel pump (2nd time) keeps mixing the oil with the gasoline and wont stay on.
What could cause this, could it be dirt in the gas tank?

This truck when built was equipped with a Rochester 4 barrel carburetor and a mechanical fuel pump. The first place that I would check would be the fuel pump. Often when the diaphragm in the fuel pump ruptures it will pump fuel back into the crankcase. Once that happens then gasoline vapors from the crankcase will be drawn up through the Positive Crankcase (PCV) Vent valve and cause the fuel mixture in the engine to rum rich. This can cause rough running and stalling at idle. If the fuel pump is OK then the problem could be a leaky fuel inlet needle in the carburetor of a sinking float. But the over flow on the carburetor would have to pretty severe to cause dilution of the engine oil. My bet is on the fuel pump.  

Classic/Antique Car Repair

All Answers

Answers by Expert:

Ask Experts


Brad Sears


All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.


Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

©2017 All rights reserved.

[an error occurred while processing this directive]