Auto,Car,truck Won't Start, diagnostic help, start test, advice

5 things an engine needs to start and run properly

1) A BATTERY with enough power to turn the engine over fast enough to start

2) A good STARTER strong enough to turn the engine over fast enough to start

3) A engine in good mechanical shape with the correct VALVE TIMING and high enough COMPRESSION to start.

4) Proper fuel air mixture delivered to engine by the CARBURETOR or FUEL INJECTION SYSTEM. No fuel, no start

5) Proper spark of high enough voltage across good SPARK PLUGS. No spark, no start .
This spark must happen at the correct time. This is called IGNITION TIMING.

Click on the above links for test procedures on all 5 essential car systems!

Some quick field tests for no start condition:

Cars that won't start usually have either a fuel supply problem or a no spark problem. A broken timing belt or chain can also stop your car dead! It won't start again until you fix the belt or chain.

Here are some easy no start tests to do:

NO START TEST 1 (non-risky)

Note: this applies to fuel injected gasoline engines. Most all engines made after 1990 are fuel injected.

Get a friend to sit in the driver's seat. Go to the gas filler cap. Remove the cap and listen to the open gas filler pipe. Have the friend turn the ignition switch on, but don't turn the engine over ( the rrrrrr sound, like you were trying to start the engine ). You should hear a whirring sound from the gas tank for a few seconds, then it should stop. This is the electric fuel pump running. No whirring sound, no running fuel pump, no start! This means your fuel pump is either bad, or the relay powering it is bad, or the computer which runs the relay is bad, etc. There are some vehicles with electric pumps where the pump only runs when the engine is being turned over by the starter. Have your assistant turn the engine over and listen again. If there's still no "whirring" sound, there's no pump action.

See my article on FUEL PUMPS for more fuel related no start information.

NO START TEST 2 (COULD BE DEADLY if you have a pacemaker, otherwise unpleasant if you get a shock: careful now!!!)

Remove a spark plug wire. Insert a screwdriver or other metal object in the plug wire end. Hold this wire about 1/8 to 1/4 inch from a metal part of the engine. Have the friend turn the motor over. (making the rrrrr sound like you were trying to start the engine). There should be a nice blue spark jumping off the screwdriver to the engine metal part (pick a part: any part).
DON'T LET THE SPARK GET NEAR THE BATTERY: IT WILL EXPLODE!!!!!!!!!!!!!!!!!!!!
CAREFUL!!!! IT CAN BITE!!!!!!!!!!!!
No spark can be from a bad coil, rotor, distributor cap , electronic igniton module, pickup coil assy., or wiring defect.

TIMING BELT NO START CHECK: MOST CARS

Remove oil filler cap. Should be able to see the camshaft. Have a friend crank the engine: No cam turning, timing belt gone for sure! If you can't see the cam, remove the distributor cap. With only a few exceptions, the distributor is driven off the camshaft. Distributor doesn't turn with motor, probably the belt is bad.

A NOTE ON BAD TIMING BELTS

When the timing belt goes bad the engine will have LOW COMPRESSION: Often it will have NO COMPRESSION! No compression, no start!

Easy way to determine low compression

An engine with LOW COMPRESSION will spin over really fast compared to an engine with good compression. As you try to start it the engine will sound differently: higher pitched, spinning a lot faster than normal.

WHAT CAUSES LOW COMPRESSION

The most common causes of low compression:

BAD VALVE TIMING, usually from a bad timing belt or chain

A BLOWN HEAD GASKET, usually from overheating. Engines with aluminum heads are especially "delicate". Get one hot and it will blow a head gasket QUICKLY!

If you do everything right on your engine it still won't last forever. Eventually the piston rings or valves will wear out and it just won't have enough compression to start anymore.

If you've got the right genes and live right, you might just live to be over 100 years old. Eventually, though, you'll die: of heart failure. The old pump just goes on for so long.

If you take care of your car and it's a good make of car you very likely will go 200,000 miles or more. Some go 300,000. One day, though, it won't start anymore: dead from low compression.

AN OLDTIME TRICK

On older motors you can sometimes squirt some oil in the cylinders and it will bring the compression up enough to start. This used to happen to the old "Detroit Iron" V-8's back in the 60's and 70's when someone would overheat them. Those motors could overheat enough to burn all the oil off the piston rings and not blow a head gasket. Newer motors blow a head gasket LONG BEFORE they get hot enough to burn the oil off the rings, so unless you've got a classic with low compression this probably won't work.

NO FUEL NO START TESTS

If you have spark and compression but the car still won't start you probably have a fuel supply problem.If in the first no start test you did above you could hear the fuel pump "whirring" then you still could have a FUEL INJECTION problem.

A QUICK FUEL TEST FOR ALL GAS ENGINES

Get a can of engine starting fluid. Any parts store has it. Spray some in to the intake manifold (removing a vacuum line is a good way) CAREFUL!!!! THAT STUFF IS HIGHLY FLAMMABLE!!! DON'T PUDDLE THAT STUFF ON THE MOTOR!!!

If the motor "tries to start" then you have a fuel supply problem.
See my articles on FUEL INJECTION, FUEL PUMPS, and COMPUTERS for diagnostics and more information on fuel no start problems.

Here's a good article on Toyota ignition and coil tests: Here's a good "no start" diagnostic flowchart

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Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment. We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry! Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.

George G. Scott, Jr.

What to do if your CAR WON'T START