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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 21
by Bob Hagin
Q. My 1980 Toyota 4X4 has the California emission control system and 92,000 miles on the odometer. The truck stalls intermittently and can happen at any time although it happens most often when driven just a short distance and then restarted after being parked for an hour or so. Our Toyota dealer kept the truck and his service manager drove it to and from work until it acted up. Their diagnosis was dirt in the carburetor even though the fuel filter is clean. The truck ran OK for a short time and then the same problem reoccurred. Next we had an independent shop rebuild the carburetor but now we are back to square one. If the truck would stop running, it would be easy to check out the different components to locate the cause. I am thinking of replacing the fuel cutoff solenoid and the vacuum switch. I noticed that in the shop manual one terminal from the solenoid valve also goes to a computer.
A. Being the doubting type, I'd first make sure that the problem was in the fuel system. As soon as the truck stopped running, I'd check to make sure that the ignition system was working by pulling a plug wire, holding it no further than a half inch away from a ground and then spin the engine. Any further than a half inch could damage the system so I'd be very careful. If it produced a spark, I'd shoot a bit of fuel down the carb air horn with a squirt-type oil can that had been filled with gasoline. If it started and then quit, I'd be sure the problem was fuel delivery. I'd look down the carb (engine off) and work the accelerator pump to make sure that the float bowl was empty. Then I'd check the fuel pressure and delivery volume, the electrics (decel valve, etc.) and the vacuum valve. There's no magic in an engine so finding a problem like yours requires a logical approach.
Q. I have a '72 Ford F-100 pickup that I use for personal yard work and to pick up materials for my home repairs. It has high miles on the 360 cubic inch V8 engine and the transmission is an automatic. After it is warmed up, the oil pressure drops and the temperature get hot.
A. The first thing to do is to change the oil and the filter. On a high-miler that isn't used very often, it's possible that the oil has been contaminated with gasoline ingested through a fuel pump that's developed an internal leak or a carb that dumps fuel into the cylinders after a shut-down. The oil pump may have a problem with worn parts that create too much clearance and hence a drop in pressure when the pump warms up. Its pressure relief valve may be at fault too. From that point on things get difficult. The camshaft, connecting rod and/or main bearings may be worn and inspecting them means major surgery. Make sure that a cooling system overheating problem isn't the main problem as this could cause a drop in oil pressure too.
Q. My son wants to become an auto mechanic and has talent in this area. His high school teachers tell me that he has a lot of mechanical aptitude and should become an engineer or something other than just a mechanic. Is the repair business a dying field? I'm told that mechanics won't be needed in the future since all the cars are computerized.
A. Since I was a mechanic for many years, it always rankled me a bit to be referred to as "just a mechanic." The trade pays very well and I found it a satisfying challenge to fix things that are broken. The engineers I know say they don't enjoy that kind of instant feedback and are usually a small cog in a big corporate machine. Education and training are the key ingredients to being a good mechanic today and that's where the system fails entry-level neophytes. If he can find a good school and a job that provides on-the-job training, he'll enjoy the trade. Even computer-controlled cars need someone to pull the wrenches.
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