Get a good shop manual, follow procedure
Dear Mike: My mechanic says that my fuel pump is bad. According to him it’s not pumping enough fuel, and that’s responsible for the misfire I get under heavy acceleration.
He quoted an astronomical price to replace it, partly because the pump is more than $200, but also because he has to remove the fuel tank to get to it. Is there some way that I can hook up a fuel-pressure gauge to diagnose this myself?
All of the fuel lines seem to be hard lines with no place to put my fuel-pump checker. Why isn’t the fuel pump mounted on the side of the engine, like it used to be?
— E.A., Torrance, Calif.
A: Your engine is fuel-injected, and these pumps generate as much as 70 to 80 psi of pressure to feed the fuel injectors. They’re sensitive to heat, so they are not mounted in the hot engine compartment, but rather placed inside the fuel tank, where they are bathed in cool fuel.
Your old fuel-pressure/vacuum gauge left over from the days of carburetors won’t work, because it reads only to 10 pounds or so. To check your pump’s output pressure, you’ll need a 100-psi gauge intended for testing fuel-injector pumps.
Most cars have a Schrader valve, like an oversized tire stem, mounted somewhere on the fuel rail to allow you to tap into the system. Some use a banjo bolt, and a few actually require you to break apart a fuel fitting. The gauge should come with a couple of adapters. This will let you check the fuel pressure — but low fuel pressure doesn’t necessarily mean a bad pump.
Your problem could be a clogged filter, a kinked line, a stuck pressure-return regulator or a half-dozen other things. The pump may make good pressure at idle, but not pump enough volume to feed all the injectors at wide-open throttle. To find out, you’ll have to do a road test with the gauge hooked up.
My suggestion is to get a good shop manual and follow the diagnostic procedure to the letter.
Dear Mike: I have a 1997 Olds LSS. I enjoy the car, as it meets most of my driving needs. It’s part comfort, part sport.
The biggest drawback I find is with the brakes — 60-to-0 in 167 feet is really bad performance. I find it hard to believe that this car does not have four-wheel disc brakes. What were General Motors and Oldsmobile thinking?
And what are my options?
— D.V., Brooklyn, N.Y.
A: The fact that your rear brakes are drum brakes isn’t necessarily the root of your problem. If those brakes are balanced properly, they should provide more-than-adequate braking capacity for a passenger car that’s not overloaded nor coming down Pikes Peak at high speed.
Four-wheel discs, on the other hand, will provide a better margin of safety for a car or truck that is heavily laden or is being driven aggressively enough to heat up the brakes to the point at which they are likely to fade.
I’d start by replacing the brake pads on the front discs with a heavier-duty compound, at the risk of setting yourself up for a squeal under light braking. Do the same for the rear shoes. And, while you’re in there, be sure that the adjusters are working properly and are keeping the shoes tight to the drums.
Flush and bleed the brake system with fresh brake fluid, according to GM’s shop-manual procedure. If you have antilock brakes, this may require the use of a scan tool to cycle the antilock pump and valves to get out the last of the air.
Dear Mike: What do you know about cryogenically freezing engine parts with nitrogen in order to make those parts last much longer than usual — and even to increase gas mileage?
This sounds like a tall claim. I read about this on the Internet. Is there any truth to it?
— D.R., Redlands, Calif.
A: This story about how someone treated his Honda’s engine with liquid nitrogen was sent to me three times in one day. Supposedly his engine lasted more than 600,000 miles and delivered nearly 120 mpg.
It’s rubbish. Urban legend.
Cryogenically treating ferrous parts is indeed a common technology. Lowering a metal’s temperature to several hundred degrees below zero and slowly warming it changes its crystalline structure, making the metal stronger and more resistant to fatigue.
But this technique won’t have much effect on an engine already designed to make the most of its components. It certainly won’t make an auto engine last four times longer than normal, or triple that engine’s fuel economy.
Dear Mike: Inspired by your recent column on removing dealership stickers, I want to tackle a similar problem.
I have a 2002 Avalanche with a plastic-coated, paper safety notice glued to the sun visor. I have read the notice many times, and will certainly be guided by it, but it’s a wart on an otherwise fine interior.
The plastic-coated paper is liquid-impervious and is on easily damaged felt. How can I remove it?
— B.C., via e-mail
A: Not all carmakers do this — some use peel-off labels. But GM hot-stamped that label onto your visor, and it’s not coming off.
You can see if you can get the dealer to order a European-spec visor, sans placard, for you. Alternatively, you can have a trim shop re-cover the visor with new felt.