No-Start diagnosis

Hey, my car won’t start,now what?Hey, bear with us, allright?We’re workin’ on it. It doesn’t take much for an engine to run, air, fuel, and spark, that’s it. Sort of. First thing is to narrow down the possibilities as much as possible. Are we dealing with a starting/charging system problem, or an ignition problem. Maybe it’s a fuel problem, or a mechanical problem that is giving symptoms of one of the others… News source: My-Page Try to start it: If the starter engages and spins the engine over and sounds like the first file, then the engine is “cranking” just fine, but it just doesn’t sound like it’s even trying to start. This means that the battery, starter, and neutral safety switch or clutch safety switch are all working fine. We can now skip half of the trouble shooting process and goto “check for spark”. If it spins unusually fast, like the sound below, (listen carefully, the difference is subtle, the first one sounds like it’s getting some resistance from the engine, while the second one is just freewheeling), then take a deep breath, and go here. If it doesn’t crank at all, check the battery, if the battery isn’t dead and the connections are clean and tight, there is a problem with the starter circuit. Try again, if it still doesn’t crank, or even click, there may be a problem with the ignition switch, starter solenoid, starter, neutral safety switch, or the clutch safety switch. Check for spark- pull a spark plug wire loose from a spark plug and get an assistant to hold it while you crank the engine. If he yells and jumps back, a good spark is present. (Just kidding, this is probably not a good way to check for spark, a better way is to pull the wire off of the plug, stick a screwdriver into the end and, while holding the plastic handle, move the screwdriver so that the metal part is close to a piece of bare metal on the engine. Then get someone to crank the engine. If there is good spark you should see a spark jump from the driver to the metal. If not, try nospark. It should be able to jump a gap of almost 1/4 inch.) If it makes a good spark and you can hear a “snapping” sound, the ignition system is probably OK, replace the wire and Check for fuel TO the engine. Whatcha got? If what you’ve tried up to now hasn’t gotten you back on the road, we’re in trouble. What we look at next depends on what we are dealing with. Open the hood. Prop it open. Look around. Is your car fairly new? look for the emissions decal. It’s almost always on the underside of the hood. It is a treasure trove of information. It will tell you the engine size, the fuel type, and often something about the engine control systems. There is even a little schematic diagram of where the little vacuum hoses go, and what the acronyms are for all those little gadgets that the vacuum hoses connect. Can’t find it? Step back and take a good look at the engine. It’s usually not too tough to figure out the path that the air takes to get into the engine, there will be an air cleaner assembly somewhere in it, probably near the inlet. There needs to be a large enough diameter path for the air to flow reasonably unrestricted to the engine. After the air leaves the air filter, but before it passes into the engine proper, it will pass through one of three things; a carburetor, a flow measuring device, or a throttle body. There may be a combination of two or more. There may be fuel injectors in the throttle body, air inlet, intake manifold, or right into the combustion chamber. You may have to remove part of the air filter to see some models. If you see a bizarre collection of strange links and levers and tiny hoses and adjusting screws all collected in the same place, chances are you have a carburetor. If the linkage is fairly simple, and the throttle plates are mounted in a housing that also contains a fuel injector or two then you are probably dealing with a TBI (throttle body injected) engine. If the engine seems to be covered with fuel injectors then you probably have some version of a Multi Point system. No spark: OK, nobody said this was going to be easy… First thing we have to do is find the distributor. It should be pretty easy to find because it will be on the other end of the spark plug wires you disconnected to check for spark. Examine the plastic cap that the wires plug into. Locate the hold down screws or clips and figure out how to remove it, it should be 2 or 3 or 4 screws or clips. Remove the cap, look at the inside, look for moisture, gray powder, and carbon tracks. Examine the center contact. Look at the rotor, wiggle it a bit, is it loose? it should be a snug fit on the shaft. Reach down and turn the engine over slightly by hand, watch the rotor, does it turn when the engine does? It better. If not, go to no rotation. The distributor rotor doesn’t turn: Uh oh, this might be serious. Actually, it IS serious. The distributor needs to be indexed to the opening and closing of the valves and the up and down motion of the pistons. This is done by driving all three parts from a single chain or belt. Either the distributor is driven by a gear cast into the camshaft or by its own driveshaft driven by the timing belt. If your car has a timing belt, (most do these days, sigh…) you need to remove part of the cover to examine the belt to verify that it is in fact broken. NOTE: It is usually fairly easy to remove the first piece of the timing belt cover, but it is always a b*tch to remove the last piece. Don’t try to cut corners, once you have the first piece off, watch the belt and sprocket while someone cranks the engine. If the sprocket doesn’t turn, you’ve got a “blown timing belt”. Gotta Carburetor, now what? If there is a single universally recognizable component of an automobile, it would have to be the carburetor. No other part approaches the complexity of the dozens of mechanical links, flaps, bellcranks and jets that all carburetors have. They look incredibly complicated. They look like they were designed by Rube Goldberg. They have all kinds of little hoses and cables going to them. There are several adjustment screws visible. DON’T TOUCH ANYTHING! Watch while someone presses the gas pedal so you can identify the throttle linkage. Watch as they push it all the way to the floor, most carbs have a link that causes the choke to be forced partially open when this is done. Look for the choke butterfly, we are gonna have to make sure it opens and closes properly, and we’re gonna have to prop it open if the engine is flooded.Your carb may not look much like this one, but you should be able to locate the throttle linkage and the choke valve on any carburetor you come across. If you can’t, either I’ve failed, or you are really du… I mean I haven’t communicated well enough. There are really only two things that go wrong with carburetors. Hard to believe, right? All those bits and pieces, all those links, cams and screws, all those jets and rods, all those valves and. . . I guess you get it, The two things that go wrong with carburetors are: 1. they deliver too much gas. or…2. They don’t deliver enough gas. The two most common reasons they deliver too much gas are; the choke sticks closed, and the needle valve sticks open. The two most common reasons they deliver too little fuel are; the choke sticks open, and the fuel level in the carb is too low. A stuck choke is pretty easy to spot, as is Fuel overflowing out the top of the carburetor, but a low level of gas in the bowl is a bit harder. Omigod, It has fuel injection! Now what? Beats me, I’ll think of something… This is a schematic of the Throttle body injection system found in many Chrysler Corporation cars. As you can see, it uses a number of input signals to determine the fuel needs of the engine and then uses the single throttle body mounted fuel injector to deliver it. It also uses some of those input signals to adjust the ignition timing and alternator charge rate. All electronic fuel injection systems work basically the same way. Once you understand which signals are used during which operating conditions you are well on the way to identifying the problem. Cold engines need a richer fuel/air mixture to run smoothly. Once the engine warms up, the mixture should get more lean. A carburetor has a choke, which closes off the air passage into the engine, which causes a rich mixture for cold operation. A FI system has a sensor that checks the engine temperature, and changes the programming of the fuel injector to richen the mixture that way. An engine with this cold engine option disabled will idle poorly, and stall at intersections, but will run fine once it warms up. Fuel system, step one: Is there gas in the tank? Are you sure? Is it getting to the engine compartment? Are you sure? Most engines these days are fuel injected, with a fuel pump either inside the fuel tank, or between the tank and the engine. The power for this pump comes through a relay, and is supplied through a fuse. If you don’t have fuel pressure in the engine compartment, check those first. Many engines have a “fuel rail” with a connection point for a fuel pressure gauge. If someone was to remove the safety cap, and press down slightly on the bicycle tube style valve pin inside, Fuel would spurt out with some considerable force if the fuel line was properly pressurized. This would of course be extremely dangerous if the Fuel was to ignite, and of course it could spray into someone’s eyes and blind them. Don’t ever encourage anyone to use this quick method for testing whether fuel is getting to the engine compartment. OK, you’ve determined that your carburetor equipped car is flooded, now what? well, you need to open the choke,( just hold it open with your fingers) then you need to hold the throttle linkage all the way open. What these two things do is to open up the air passage as completely as possible, allowing the maximum amount of air to get to the engine. You need this air to dry up the raw Fuel that is laying all over the inside of the manifold and cylinders. Now get someone to crank the engine. It should start after a few seconds and you’ll need to fart around with the throttle a bit to keep it from dying until the idle smooths out. Put the air cleaner back on and get on with your life. 90% of all flooded carburetor engines will respond to this technique. ASSUMing of course that you haven’t run the battery dead in your vain attempts to start it… Here is a diagram of a F*rd Multi-Point system, not a lot different from the simple system shown above. Still a logic unit getting a lot of input from sensors and then controlling some fuel injectors to deliver the correct amount of fuel to the engine. You probably won’t be able to read much of the printing, but some of the components are the fuel pump relay, the fuel injectors, throttle position sensor, oxygen sensor, atmospheric pressure sensor, knock sensor, EGR position sensor, etc. If your symptoms only appear in the morning when your engine is cold, you need to look at the sensors that tell the system how warm the coolant is, as well as the extra injectors some systems use for cold enrichment. If your problem seems to only happen at a certain throttle position maybe you should look at the throttle position sensor. Hey, this isn’t rocket surgery… Timing Belt? If your engine spins unusually fast when you try to start it, but it doesn’t even cough or sputter, you’ve probably blown your timing belt. This is not a thing that you wanted to discover today. The timing belt is there to drive the camshaft, which opens and closes the valves. It also has the function of keeping the camshaft and crankshaft properly aligned with each other to establish the “valve timing” (the relationship between the opening and closing of the valves with the piston’s up and down motion.) Valve timing is essential for the engine to run at all, as you have just discovered. When the camshaft stops turning, the valves freeze in whatever position they are in at the time, but the pistons keep going up and down as usual. The distributor stops turning, so the spark plugs stop firing. The geometry of the camshaft causes it to stop in one of a small number of positions, equal to the number of cylinders the engine has, resulting in at least one valve at least partially open in almost every cylinder. This causes the compression to be low for all cylinders, which is what causes the engine to spin so fast when you’re cranking it. Some engines, (called “interference” engines) are designed in such a way that when this happens, at least one valve is hit by a piston when it reaches the top of the stroke, which of course bends the valve and reduces the compression on that cylinder to zip. This means that the head must come off, the bent valves replaced, the timing belt replaced, sometimes the pistons are damaged and they must be replaced also, as you can calculate, it’s much cheaper to replace the belt before it blows on these particular engines. This is often mentioned in the owners manual, in the maintenance section, you did read the maintenance section didn’t you? Inside the distributor cap: There are two main things we look for inside the distributor cap, one is moisture on the inside surface, which allows the spark to jump directly from the center contact to ground instead of going through the rotor and out to the spark plug wire and plug. The other main thing we are looking for is carbon tracking or damage to the rotor. Carbon tracks look like lines drawn on the inside surface of the cap with a pencil, they will either go from one contact to another or from a contact down the side of the cap to the bottom. Remove the rotor, sometimes this means loosening a screw or two that holds it in place, but usually you just pull it straight up. Look at the bottom surface, look for carbon tracking or any burnt or otherwise damaged areas. If in doubt, replace them, they are just about the cheapest parts you are ever likely to buy for your car.