A Buick Skylark and a Ford F-150

Question: 1991 Buick Skylark

I don't have a problem, just need an answer please. I've had this car since 12,000 miles, and the oil is "always" black after driving it even after an oil change. What's up?

• 1991 Buick Skylark
• 3.3V6
• Automatic transmission
• 74,000 miles
• Fuel Injection
• P/S, A/C, Cruise control

Answer:

Years ago, I had a customer accuse me of not changing his oil like I was supposed to because of this. So I did it again while he watched; he still couldn't believe the oil still turned black after running a short time.

Even when you change the oil, you never get ALL the oil out. There is always a bit left in the engine to discolor the new oil. This is fairly normal in most engines. A lot depends on the motor oil you use also. Some motor oils are dark and appear black when in the engine. Some motor oils are light colored. Gasoline quality is a factor as well. A gasoline with high sulfur content will turn oil black. Just look at the oil in any diesel engine and you'll see what I mean. A gasoline with a low sulfur content will not turn the oil black.

Less than frequent oil changes will cause it as well. Contaminants will accumulate in the engine and build up. So when the oil is changed, the new oil will clean up some of these contaminants and turn black. More frequent oil changes will clean the engine up. I have customers who have brought their new cars to me since the first oil change, and on a regular 3,000-mile schedule, and the oil comes out just as clean as it went in. My 1987 Nissan Van with 160,000 miles on it is like that; the oil comes out just as clean as when it goes in. The oil in that gets changed every 3,000 miles.

If you got the car with 12,000 miles on it, it hasn't had time to get really dirty, and changing the oil at 3,000 mile intervals will probably clean it up to the point where the old oil will come out as clean as when it goes in. But even if it doesn't, you don't have to worry too much about internal engine damage.

Question: 1990 Ford F-150

Dear Mr. Ciulla:

I own a 1990 Ford F-150 pick up 6-cylinder engine, 2-wheel drive and automatic transmission. I am the original owner, bought it new. Truck, as always, runs right because I take good care of it. Last summer I replaced the fuel pump and gas tank with new ones. The repair went great. The truck started up and ran great until about 2 weeks ago. The truck would not start, but would turn over fine. I immediately listened for the humming of the fuel pump motor in the fuel tank and the clicking of the fuel pump relay. No sounds from either source. I have working spare fuel pump relays, so I switched them; still no sounds from fuel pump relay and no hum in the tank.

I then checked the voltage of the fuel pump hot wire and got 8.56 volts. I should have gotten 12 volts, right? I then checked the continuity of the hot wire of the fuel pump from front to rear; there was none, so I ran a new jumper wire front to rear. I took the old wire completely out of circuit.

I rechecked for voltage at fuel pump connection and got 12 volts. Truck would still not start. I checked the fusible links; no signs of burning, ignition relay, ECM, and coil are working fine. I checked all the grounds in the engine compartment for continuity and they all passed. I checked the ground of the fuel pump in the tank and that passed too. Not to sure what to do anymore. Please advise.

Thank you,

David L.Valyo

Answer:

Okay, first thing I would do is check for fuel pressure at the fuel rail to assure me that it is indeed a fuel pump problem. And I'm assuming you have a single fuel tank and not dual fuel tanks. If you are getting 12 volts at the fuel pump and the fuel pump ground is good, and the fuel pump itself is good, it has to run. If you have the 12 volts and good ground and the fuel pump doesn't run, then, without question, the fuel pump is bad. If that is the case you need to replace the fuel pump. I have seen, too many times especially with aftermarket parts, fuel pumps go bad after a month or so.

The fuel pump circuit has an Inertia Switch, which is located at the left hand dash panel above the brake pedal, that may need to be reset. Just push the button on the switch to reset it. But if you went from the relay directly to the fuel pump you would have bypassed the inertia switch.

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