Wednesday, June 22, 2011

The car will not start?

Tips on how to troubleshoot a car "no start" condition

Here are the basics on getting a car to start:
1. Turn over (crank)
2. Fuel
3. Fire (spark)
4. Ignition and valve timing

Let's go thru each one. You can obviously scroll if you have already ruled some of these out.

1. Due to the length of the "No Crank" .
Click this link to troubleshoot NO crank issues:---
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2. Assuming the engine cranks, next check for fuel. A good first check if fuel delivery problems are suspected is to spray some starting fluid into the intake system while someone cranks the engine. If the engine starts or tries to start with starting fluid, it is not getting fuel. In most modern cars, the fuel pump is inside the gas tank and is also usually sold with the fuel gage sending unit--an expensive and laborious R&R job. If the pump is working, you should hear it at least momentarily when the key is turned to the "on" position. If the pump is not working, the cause could be a fuse, a relay, an accident "kill" switch that needs resetting, or the pump itself. You'll want to rule out all of the inexpensive possibilities first. Use your owners manual (you can often find these online if you don't have the original) to locate the applicable fuse, relay, and/or cutoff switch. To check the relay and ignition switch, click the link below:---
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You can also check for voltage at the pump connector with a test light.
Assuming your pump works, fuel still needs to get to the engine. A clogged filter will certainly limit fuel flow, but will rarely prevent a car from starting. That said, filter replacement is an inexpensive bit of maintenance. Most likely cause of fuel not getting to the engine when the pump is working is the fuel injection system (not an issue for carbureted engines). Injection systems are beyond the scope of this tip, but there are a couple things you can check. Many anti-theft systems cut off the injectors when activated. If you have such a system, make sure your anti-theft system has not been activated. Also, the injectors require a certain level of fuel pressure. Though your pump may be working, it may not be producing pressure. If possible, check or have your fuel pressure checked at the fuel rail. Some designs include a schrader valve on the fuel rail for pressure tests. You can carefully push in the valve stem for a crude pressure test. The injectors are usually controlled directly by the engine or powertrain control module/computer. The signals sent to the injectors can be checked using a special tester or oscilloscope. A simple but crude method of checking injector operation is to put a long screwdriver on the injector body and hold the handle to your ear while someone cranks the engine. If the injectors are working, you should hear the solenoid click once every 2 revolutions.

Finally, if you are getting fuel to the engine, make sure it isn't old or contiminated.

3. Assuming you have crank and fuel, check for fire. An easy way to check for spark is to pull an ignition wire from the coil or distributor and hold it with an insulator (oven mit or pliers with plastic grips?) close to the terminal you removed it from while someone cranks the engine. You may have to push the wire into the boot to expose the terminal or use a Phillips screwdriver to reach into the terminal to get the spark out of the boot. Here is a pic on how to do that:



If sparks jump across when cranking the engine, you have fire. If you have fire at the coil/distributor, you must still verify that the ignition wires are properly connected to the spark plugs. This is especially important in cases where the plugs or wires were replaced just prior to the "no start" condition. Look up the firing order specifications for your engine and verify that the wires are connected in order.Click this link below for firing order testing help:----
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If you do not have fire, use a (12 volt) tester to check the coil terminal for ignition power. The coil voltage varies from car to car, but should be between 9-15 volts. If there is no voltage to the coil with the key on, check the ignition fuse and relay. Not all vehicles have an ignition relay, but if your does, you can click this link and follow the testing procedure:---
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In these designs, the command signal from the ignition switch may be negative or positive. If you aren't sure, see if you can get the wiring diagram for the circuit. If the command signal is not getting to the socket, your ignition switch or ignition wire from the switch are bad. If the command signal is getting to the socket but the relay is not clicking, replace the relay.
Assuming now you have power to the coil but no fire, either the coil is bad or the ignition module is not sending the timing signal to the coil. If you have more than one coil, check them all. This is a good way to isolate and identify individual coils for replacement. Ignition modules are beyond the scope of this tip, but I can provide a few ideas on where to start. It is a good idea to extract any and all fault codes indicated by the "check engine" light when you are not getting a spark from a powered coil.Click this link to about getting check engine light problem solved:----
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Use the fault codes to further troubleshoot the ignition system. It is advisable to get the wiring diagrams for your ignition system to troubleshoot. If you have a fault code relating to the crankshaft sensor, this fault may prevent the computer from timing the spark. Check the wiring and connector to the sensor and make sure the sensor is tightly installed.

Most modern cars have an engine or powertrain control computer/module to send signals to the ignition coils and fuel injectors. If you have an oscilloscope or other meter that can sense a waveform, use it to check the signal to the negative coil terminal(s). If the signals are not rectangular and periodic, suspect your ECM/PCM is bad or is getting bad data from the crankshaft sensor. Knock sensors may, in some cases, also affect the computer output, though these are generally used only to modify the ignition timing while the engine is running with a knock.
If your car is a bit older, it may just have a distributor with a pickup coil and ignition modulator to generate the signals to the coil. In these systems, the modulator charges the coil and then cuts the charge signal when it receives a blip from the pickup coil in the distributor, thereby releasing the spark. The spark then travels from the coil to the distributor and is routed to the appropriate ignition coil via the rotor. The signal to the coil should still be rectangular, and if not, suspect the modulator is bad.

4. Timing. The spark plugs must fire when the cylinder is on the compression stroke or the cylinder will not fire. In many cars, the timing is controlled by the computer (in such cases, a possible cause for bad ignition timing is failure of the engine control module/computer or the knock or crankshaft position sensor). In others, there is a tab with numbers next to the crankshaft pully and a mark on the pully or vice-versa. If the timing is somewhere between -8 and +2, the engine should fire. Where it is adjustable, there is a specified value and method for setting the timing for optimal operation. A timing light can be used to check the timing while cranking the engine. Use chalk to mark both the moving and non-moving marks that you need to line up. Ignition timing is usually not a reason for a "no start" condition, unless someone has changed the setting or removed the distributor before the condition arose.
The valves must also be properly timed for the engine to fire up. A typical failure in valve timing is for the belt or chain to slip a tooth or 2 on the crankshaft gear. In some cases, the belt may lose all of it's teeth in a short region of the belt and just stop turning the camshaft completely. If the chain/belt slips a tooth or two, the car may start but will have much reduced power and may backfire or shoot fuel/air mixture back up the air horn. This behavior is a strong indication of slipped valve timing.
Slipped valve timing can also be damaging to the engine if your particular engine design is what we call an interference engine. In such engines, it is possible for the valves to hit the pistons when the valve timing is off. For this reason, if you suspect a valve timing issue and you don't know if the engine is an interference design or not, do not attempt to start the engine. Instead, remove the timing cover and check the gears for proper timing. Consult a manual or contact us for a picture of the timing marks. In some overhead cam engines, it may be possible to remove just the upper timing covers to check valve timing. If your valve timing has slipped, replace the belt or the chain/gear set. Make certain the timing is correct before closing up the engine.

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To Order car parts online:--To get heavy discount on car parts .Click this link below:----

http://technoanswers.blogspot.com/2011/05/from-where-to-order-car-parts-online.html

For car error code diagnosis click the link below:---

http://www.automd.com/diagnose/?amdcid=apwldrbrd1

Car no start:--

http://technoanswers.blogspot.com/2011/05/car-will-turn-over-but-will-not-start.html

2 comments:

  1. Thanks for this basic troubleshooting tips this will surely help a lot.

    Distance Sensor

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  2. just got this truck wont start . i bought it had to jump it when bought it . had bad battier then put gas in because it had not gas in truck. so i put 10.00 in drive it 4 miles let it run 15 mins after . we got home . the next morning . we put the size battier. it wanted about 10 mins . i have not got it to start . the start is not bad

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