Sunday, March 4, 2012

30 Car Mysteries Solved: Spark Plug and Battery Testing

I turned the old pickup's key and knew instantly--it was dead. There was no juice left in the battery. Someone had rescued a garage-find dead battery, charged it and shoehorned it into the truck on the cheap. The bad battery fried the aging alternator, and it wound up in my shop for a charging-system transplant. Hours later, after a new battery and alternator had been installed and I'd chased a couple of parasitic drains, the engine still wouldn't start. I'd been tinkering around in the fuse box, so I figured I had jiggled some of the shaky wiring harness loose. In these situations, one of the first things to do is check for spark. Just pull a plug wire, clip on the spark tester, crank the motor and look for spark jumping the gap, right? There's an easier way: the OK Spark plug tester.



Just hold the tester's probe near a plug wire (or even near a coil-on-plug coil assembly) and you can tell if the plug is firing. It will even detect a fouled plug, something a conventional spark-gap type of tester won't do without removing the plugs. It's a huge time-saver. I just had to hold the probe near any of the plug wires while someone cranked the engine. I found my problem in the injection harness easily, knowing for certain I had spark. OK Spark means you don't have to pry stubborn plug connectors off, keeping you clear of the engine's red-hot exhaust manifolds.





Water Shortage

Q:

Three months ago, my seldom-used 1985 Chrysler New Yorker steamed up under the hood. When it cooled off, I discovered that all the coolant had gone. After refilling and checking it regularly, I found none was leaking on the ground. Yesterday the same result: no coolant. Where does it go? Presumably it disappears only when I am driving.



A:

That coolant is leaking, for sure. And it's leaking one of several possible ways. It could be going into a combustion chamber and leaving as steam through the exhaust ports. Or it's leaking into the oil. A small leak would leave the oil mostly water-free, as the PCV system will pull a lot of moisture out of the system if the vehicle is driven far enough to warm the oil to around 180 F and keep it there. One other possibility is that, once hot, it's leaking in small amounts either as steam or onto a hot spot (like the exhaust manifold), where it will evaporate without leaving a wet spot. Also, a tiny leak in the intake manifold gasket might get into the manifold itself, where a small amount of coolant could simply be sucked into the combustion chambers, turned into steam and--buh-bye. You hope that's the case, because the other possibilities would mean pulling the cylinder heads to replace the head gaskets, which would probably cost more than the car is worth.



There are ways to chase these leaks. The easiest is to pressurize the cooling system with compressed air and listen for the hissing at the exhaust pipe, the oil filler cap or the top of the carb or throttle body. Stant and others make an adapter to fit the radiator neck with a hand pump and a gauge. Just pump up the system and start chasing leaks. Trouble is, some leaks only leak when the engine is up to operating temperature, so don't burn yourself. If that doesn't work, you may need to add fluorescent dye to the system and use a UV light and yellow goggles, CSI Miami-style.



Troubling Transmission

Q:

I have a question about my 1997 Eclipse Spyder (it barely has 80,000 miles on it). Recently, when I get ready to leave my house, I push down the clutch to start it and it seems to require way less force than it used to. Then, when putting the transmission in reverse to back out of the driveway, it grinds a little. If you try a few times, it will eventually go into gear with no problem. After a few shifts, the gearbox starts to act normally. What's going on?



A:

Your Eclipse, unlike many vehicles that use a mechanical linkage or a cable, uses a hydraulic clutch actuator. Air in the hydraulic line is keeping the clutch from disengaging sufficiently. A few pumps will purge the air, but it seeps back into the master cylinder overnight. I'd start by flushing out the old fluid (actually, just DOT-3 or DOT-4 brake fluid) and bleeding the system thoroughly. If that doesn't fix it, you've got a leak that's sucking in air. Rebuilding or replacing the master and slave cylinders should cure it.



Fuelish Solution

Q:

I have old premixed boat gas; 8 gallons of it, mixed 50:1 with oil. It's too old to use in my two-cycle outboard. Can I put it in my 1997 Land Cruiser? I figured I would dump the mix in with the tank half full and top it off with fresh fuel afterward, or do it 4 gallons at a time for further dilution. Will it foul my fuel injectors with that bit of oil? Or should I just throw it away?



A:

Gummy, old, oxidized premix gasoline is a poor candidate for use in a modern, catalytic-converter-equipped car. Come to think of it, so is old, oxidized gas without the extra two-stroke oil, too. The oil can potentially contaminate an expensive cat, and any varnish (produced when gasoline oxidizes, in the same way that oil-based paint cures) might foul the fuel injector pintle valve(s), which are also not cheap to replace. No, the fuel filter won't catch the varnish. And if it did, you'd need to change the filter soon, and that usually involves removing the gas tank from the car, which will cost far more than your out-of-date fuel.



Plus, there's the problem of phase separation caused by water making any ethanol drop out of the solution. Odds are any fuel stored in a container that's not perfectly sealed will soak up atmospheric moisture. This will leave you with a layer of water and ethanol in the bottom of the tank and a layer of cloudy gasoline floating above it--and neither layer will burn well enough to run your, or any other, engine.



Adding more alcohol (gas line drier, like Heet or Dri-Gas), the traditional solution for water in the gas, won't work. There's nothing you can add to remove the oil or water.



My advice? Call the local DPW or fire department and find out a safe, legal way to dispose of the fuel.



Self-Taught

I recently did some work on my old 1996 GMC pickup that had started to run erratically. It seemed to be dropping a cylinder and losing power. I checked for fuel and spark ... I pulled the plugs, etc. I suspected a cylinder was not firing, but the plugs all worked fine.



Then, I went to looking for a bad injector, without a scan tool. Well, using one of my R-12 Freon gauges, I hooked up to the fuel-pressure rail (Schrader-valve type). Then I turned on the key and watched the pressure go up and remain steady. After gaining access to the multiconnector for the fuel injectors on top of the intake plenum, I one by one ran a hot lead jumper to each of the eight connectors. Each time I did that, the pressure gauge would drop as I opened the injector--except for one particular cylinder. Was that one cylinder the culprit and the reason for the dropped power and low-speed miss?



After further investigation, I found that replacing all the injectors was better than replacing just the faulty one. Either of these two individual components could have been defective, and the cause of my problem. With most of the labor involved in accessing the fuel injectors, I felt it was more prudent to replace them all with new (and better designed) units rather than only one cylinder's worth. The new ones differ from the originals, in that the injector and poppet valve are made from metal and are an integral unit. The original GM design consisted of plastic components, with a solenoid section and poppet valve that are separate from each other. Eight new ones obviously cost more. However, with the 350,000-plus miles on the original injectors, others were sure to fail in the near future. After it was all said and done, I had a neighbor who has a scan tool hook it up to read the codes and zero them out, just to make certain nothing else was happening that I didn't know about.



Couldn't have said it, or done it, better myself. The flat-rate book says that replacing a single injector takes 2.6 hours, and only another 18 minutes to replace them all, so it makes sense to do all eight at that kind of mileage. The only thing I might add is that if you fixed the bad injector, the Check Engine light would have gone off on its own after a couple of engine start-stop cycles. Or you could have pulled the engine-control-module fuse for a few seconds, or even just lifted the battery negative post to clear the code. 



1 comments:

  1. Hello,

    This is really interesting take on the concept. Difficulty cranking, low momentum while running or sluggish performance in your engine can all mean spark plug failure. It helps to save your fuel costs, avoid side-of-the-road breakdowns and keep your car from needing even more expensive work caused by neglect of the spark plugs and ignition/spark plug wires. Appreciate your work, keep it up.....

    Pressure Calibration Equipment

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