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. 

30 Car Mysteries Solved: Trailer Turn Signals

Q:

I just picked up a nice used camper trailer. The turn signals all light up, but they flash about three times per second instead of once every 2 seconds. The gentleman who sold me the trailer claims it worked just fine with his truck. My mechanic can't find anything wrong with my car--but I can't even tow the trailer over to him until I get the lights working.

A:

You need to upgrade your flasher relay to a heavy-duty flasher. Here's how those old-fashioned flashers work. There is a set of switch points attached to a bimetal strip, all in series with the turn-signal bulbs and the battery. When the turn signals are switched on, current flowing through the bimetal strip heats it up, and the strip starts to curl, breaking the circuit. A second or so later, the strip cools off, making the connection again, a sequence that repeats until the signals are canceled. Plug in the trailer, and you're adding two more filaments to draw more current, which makes the bimetal strip heat up faster, accelerating the blink rate. Go down to the auto parts store and get a flasher rated for towing. It costs around five bucks and plugs right in under the dash. Can't find it? Turn on the signals and follow the click. The heavy-duty flasher either uses a circuit that isolates the bimetal strip from the load, or just does the whole thing electronically.

I sometimes get letters from readers who can't hear the flasher relay at all, regardless of how fast it's blinking. A lifetime of rock-and-roll, high-caliber handguns, motorcycles and race cars is starting to affect my hearing, too.

Fortunately, you have an option. They make special, louder flasher relays that are also dirt cheap. Just substitute one for the old flasher.

Here's the bad news. Many modern vehicles have integrated the flasher-relay function into a fancy-dan lighting-control module, or whatever they call it, and you're stuck with what's built into it. Most of these vehicles will handle a trailer, but the volume of the flasher is fixed. I bet a decent mechanic or one of those shops that installs car stereos could splice in a chime or a buzzer or something, probably for a lot more than the cost of a new relay.

Best (or at least cheapest) solution I've seen was a fellow who epoxied the lid from a tuna can to the standard flasher relay, making a sounding board to increase the volume substantially.

Altitude Correction

Q:

My home and shop are at an elevation of 8000 feet. How does this change my readings when doing a compression test on my car?

A:

Compression readings are done by removing all the spark plugs, attaching a compression gauge to an individual cylinder and cranking the engine to measure the maximum pressure built up in the cylinders.

Expect the readings to be lower at altitude than at sea level. Normally, I'd expect to see readings somewhere between 120 and 160 psi at sea level, but the number will vary, determined by your car's compression ratio and camshaft timing. Depending on the altitude, the barometer reading on any given day and how robust your battery is, the actual readings you get on a compression test can vary 10 to 15 percent up or down. What's far more important is the consistency between the cylinders. If they're all a few pounds low, it might be that your battery is just a little discharged, or the barometer is low, or the throttle valve isn't propped open far enough while cranking the engine. If only one is weak, the condition might be indicative of a burned valve, leaky ring or scored cylinder wall. If two adjacent cylinders are very low, I immediately suspect a blown head gasket between them.

Counterintuitively, high-performance engines often show lower compression readings because the hot camshafts leave the valves open well past bottom dead center, lowering the effective compression ratio.

A number of late-model cars can replicate a compression test without removing the spark plugs. Under the command of a technician armed with a scan tool, the computer disables the cylinders one at a time in some sort of random sequence. After a few minutes, it will return a "Cylinder Balance" result. The cylinder(s) with low compression will affect idle speed less than the others when switched off, pinpointing any problems. I still like to do a compression test or leak-down test, because it gives me a chance to look at the plugs.

Locked Out

Q:

I own a 1969 Ford with a 428 Cobra Jet engine and the car constantly stalls. It has a mechanical fuel pump and "hard" fuel lines from the pump to the carb. I checked the fuel pump pressure and it reads 7 pounds. The car drives anywhere from 1 mile to 20 miles before it stalls. My next fix is to replace the fuel pump, but I am wondering if the car is suffering from vapor lock. It is a big block with long tube headers, so it certainly gets hot under the hood. The fuel line does not touch the block or manifold at any point. The car had a rubber fuel line from the pump to the carb when I purchased it, but it was not installed any farther away from the block or manifold than the hard line. If it is vapor lock, would changing back to a rubber fuel line solve the problem?

A:

I agree, it's probably vapor lock, caused by liquid fuel boiling in the carb or fuel lines, preventing sufficient liquid fuel from reaching the jets. The vapor pressure of gasoline is much higher than it was in 1969, since we use a lot more of the crude oil in the barrel, including a higher percentage of more volatile fractions that used to be flared off. And it's those fractions that boil at lower temperatures than the rest of the fuel. Fortunately, fuel-injected cars aren't prone to vapor lock because the fuel in the engine compartment is usually between 30 and 60 psi, not the seven or less used by carbureted vehicles.

Changing back to a rubber line and moving it away from the headers might help reduce the temperature of the fuel inside the lines. Just insulating the hard line might be enough to prevent boiling. The fuel is probably actually boiling in the float bowl, however, not in the line. They make insulated base gaskets for those carbs, and some cars with carbs used sheet-metal heat shields to keep heat from the headers from radiating into the carburetor.

Toward the end of the carburetor era in the '80s, some manufacturers resorted to recycling some of the fuel from the fuel pump back to the tank. This was done with a tee fitting that had a small restriction in one leg of the tee, allowing a small trickle of fuel to go back to the tank through a separate line. The cool fuel from the tank, moving continuously through the line, kept the fuel from boiling. This required a fuel tank with an additional fitting for the return line. You might check if your tank could be modified, or replaced with a later model tank with the fitting. Come to think of it, the fitting was often in the fuel sender plate, so all you might have to change is the fuel sender for one with the extra fitting, and then run an additional line from the engine compartment back to the tank.

If you have air conditioning, you might try my favorite fix: Wrap the fuel line around the cold a/c refrigerant line as the refrigerant line heads back to the compressor from the evaporator. Strip off the insulation, wrap the hose around the cool line, and rewrap with fresh insulation. I'll bet that if the engine is hot enough to vapor lock, you're hot enough to need the air conditioning on.