Home       FAQ Main Page      Contact       Search






My car won't start, starts then stalls, stalls a lot while driving, or just runs badly
you came from Master Index > Start/Running problems




Introduction
The basics: How to check for spark and fuel
Symptoms (choose the specific problem you have)

Credits to those who provided  invaluable help in the construction of these pages.



Introduction
back to top of this page

Starting/stalling problems can be difficult to diagnose, since there can be many confounding variables, such as poor maintenance, and/or cheap aftermarket parts. With this in mind, I've decided to set up this page by listing symptoms, along with their most likely causes. There are two basic categories:

By the way, ANY time you try diagnosing a problem, try the BASIC, cheap, easy stuff FIRST! The worst thing you can do is randomly throw money and parts at the car, hoping a shotgun approach will fix it. "Spray-and-pray" usually doesn't work.


The basics:
back to top of this page

A car needs five things to start and run:
The first item is easily eliminated: If the starter turns (the normal "chugga-chugga-chugga" noise when you turn the key), then this part is most likely fine. If all the other engine systems are in decent shape, the engine can be turning as slowly as 6 rpm and still start. The other items have to be present in the right amounts, at the right time. A failure of amount or timing in any one will prevent the car from operating correctly. Air supply is usually a given, and usually not problematic in most cases (EGR aside).

Issues are most likely to arise with the spark and fuel (and 90% will be spark), so solving starting and stalling problems should begin there, after you've made a general inspection to make sure all hoses and wires are connected, and that the air filter isn't clogged solid with dirt.

A warning here before we go any further: If you're using an aftermarket distributor cap, rotor, igniter, coil and/or plug wires, be aware that quality is variable and they are unlikely to be anywhere near OEM standard, even if they're sold as "premium". There's a reason such parts are cheaper. Poor-quality aftermarket parts can (will) cause their own problems that can greatly complicate diagnosis of starting problems. For the little extra cost, new OEM is always the safest. Also, never crank the engine with the plug wires removed, or with the distributor cap off, except for brief (very brief) testing purposes. Doing so can overheat and damage the ignition coil.


The symptoms:
back to top of this page

Click one or all that apply:
(Causes marked with an asterisk * are the most likely ones you'll encounter)

You turn the key to START, and all you hear from under the hood is a "click" or "click-click-click...", or dead silence
Car cranks (you hear chugga-chugga from under the hood), but it never feels like it wants to "catch" and fire up
Car cranks and feels like it sort of "catches" once in a while, but never actually gets running
Car starts when cranked, but stalls as soon as you release the key. Will restart if you let it sit a while
Car cranks, starts, but runs poorly and roughly, then stalls
Car starts and runs fine, but once on the move stalls suddenly and randomly. It restarts with no trouble
Car is fully-warm, stalls suddenly while driving, then won't restart unless you let it cool down for a while
Car starts, runs, but runs poorly with low power and lousy gas mileage. Smoke or raw-fuel smell may be present


You turn the key to START, and all you hear from under the hood is a "click" or "click-click-click...", or dead silence
back to Symptoms

Honda-specific
Ignition switch

Generic to all cars
* Battery discharged
* Battery internally shorted (dead silence only)
* Battery positive/ground cables dirty, frayed, loose, or disconnected
* Starter defective or worn
Fuse/fusible link blown (dead silence only)
* Poor maintenance, neglect, incorrect servicing
Starter solenoid bad

Car cranks (you hear chugga-chugga from under the hood), but it never feels like it wants to "catch" and fire up
back to Symptoms

Honda-specific
Igniter
Coil
PGM-FI Main Relay
Distributor rotor resistor blown
Dirty/worn distributor cap

Generic to all cars
Spark plug wires old and leaky
Poor maintenance, neglect, incorrect servicing
Ignition wires disconnected or installed incorrectly
Engine flooded with fuel
Out of gas (don't laugh, it happens more often than you think)
Low or no fuel to injectors
Timing belt incorrectly installed
Dirty or oil-soaked spark plugs


Car cranks and feels like it sort of "catches" once in a while, but never actually gets running
back to Symptoms

Honda-specific
Ignition switch

Generic to all cars
* Spark plug wires old and leaky
* Poor maintenance, neglect, incorrect servicing
Engine flooded with fuel
* Low fuel pressure to injectors
Dirty or oil-soaked spark plugs


Car starts when cranked, but stalls as soon as you release the key. Will restart if you let it sit awhile
back to Symptoms

Honda-specific
* PGM-FI Main Relay
Ignition switch

Generic to all cars
none


Car cranks, starts, but runs poorly and roughly, then stalls
back to Symptoms

Honda-specific
Coil

Generic to all cars
* Spark plug wires old and leaky
* Poor maintenance, neglect, incorrect servicing
Engine flooded with fuel
EGR valve stuck open
Dirty or oil-soaked spark plugs


Car starts and runs fine, but once on the move stalls suddenly and randomly. It restarts with no trouble
back to Symptoms

Honda-specific
* Ignition switch
* Igniter
Coil
Loose wire

Generic to all cars
Loose wire


Car is fully warm, stalls suddenly while driving, then won't restart unless you let cool down for a while
back to Symptoms

Honda-specific
Ignition switch
* Igniter
* Coil
Loose wire

Generic to all cars
Coil
Loose wire


Car starts, runs, but runs poorly with low power and lousy gas mileage.
Smoke or raw-fuel smell may or may not be present
back to Symptoms

Honda-specific
Coil

Generic to all cars
Coil
* Spark plug wires old and leaky
* Poor maintenance, neglect, incorrect servicing
* EGR valve stuck open
Timing belt installed incorrectly
Dirty or oil-soaked spark plugs





Battery discharged
(use your browser's "Back" button to return to where you were)

Most people think that if they check the battery's voltage and they get around 12V, that the battery' is charged up. It may NOT be!

A standard automotive lead-acid battery measures 12.65V. If you get less than that, it's not charged properly.

Test it using Bill Darden's famous Battery FAQ advice:
http://www.batteryfaq.org/



Battery positive/ground cables dirty, frayed, corroded, loose, or disconnected
-or-
Starter defective or worn
(use your browser's "Back" button to return to where you were)

Easily diagnosed:
Turn the headlights on. Go stand up front while a helper cranks the engine.
(If you have no helper, use the interior dome light as your tell-tale.)


When key is turned to START:
By the way, it's normal for the lights to dim slightly as the starter operates. If the starter sounds like it's otherwise working normally, then you can disregard slight dimming of the lights.

You can check the starter's internal resistance with an inductive ammeter. Any more than a couple of hundred amps means starter motor trouble.

A "click" or "click-click-click" means the solenoid is trying to grab and hold, but it can't. If it can't, the motor can't turn, since it gets its current through the connected solenoid. A solenoid that won't grab is either defective or the battery is too discharged to allow it to grab.

It's easy and cheap to disconnect the battery ground cable and the live feed to the starter, and clean all the connections back to bright metal. Don't forget the engine-to-chassis ground cable! If this gets broken, it can cause starting electrical problems in itself.

Engine flooded with fuel
(use your browser's "Back" button to where you were)

A "flooded condition" may be accompanied by wet spark plugs, and/or a strong fuel smell from the exhaust while cranking.

Occasionally, injectors leak. It's somewhat rare, but it does happen. No-starts due to this seem most often to occur after the car sits overnight. Brand-new injectors will sometimes need to wear in, to "seat" properly. Older cars, especially those not driven much, that have had poor maintenance, or that have been allowed to run out of gas once too often, can have gummed-up injectors whose pintles don't fully seal the spray hole when closed. When this happens, the fuel/air mixture in the cylinders can become so rich that the spark plugs have trouble igniting it.

Flooding can also happen if the ignition wires are in poor enough condition that they fail to allow the spark plugs to ignite the fuel in the combustion chamber.

The cure? Push the accelerator pedal to the floor and hold it there while cranking. The computer recognizes your action as an attempt at clearing a flooded condition, and shuts off the injectors. You might have to crank for a minute for it to work its magic. This method is listed in your Honda Owner's Manual.

If your flood control worked and the car started, run some high-octane gasohol (Sunoco 94 is good) for a couple of tanks, or add a bottle of Chevron Techron (about $12) to a tank of gas. It may be just enough to clean up marginal injectors.



Spark plug wires old and leaky
(use your browser's "Back" button to return to where you were)

This subject really ought to go in the "Poor maintenance" section, but it's prevalent enough that I thought it needs its own writeup.

Spark plug wires have a hard job. They must reliably conduct 30,000 volts or so to your spark plugs from six to 60 times per second. They have to do this no matter the weather, heat, or vibration under your hood. Keep in mind that modern plug wires don't actually have a solid wire inside, but a sort of carbon paste, which is easily damaged from mishandling. An actual copper wire would cause too much radio interference, and your favorite music would be inaudible.

Usually the first thing to go bad, at about five to seven years or so, is breakdown of the insulating rubber. Once this happens, moisture will seep into microscopic cracks in the rubber and provide a leak path for the current before it manages to reach the spark plugs. You've probably gathered by now that problems involving old wires would show up mostly in wet or humid weather, and you'd be right. This gives us a clue to diagnosis, and a clue to a solution.

Diagnosis:
Cure:
Yes, I know OEM seems overpriced compared to what you can get from the aftermarket, but what's reliability worth to you? Wires need to have a certain specified resistance to play nicely with the other components of your ignition system. Bad wires (and other interruptions of HT current flow) can kill your coil, and aftermarket wires can break down much faster than OEM. Resistance should be below 25,000 ohms for most Honda wires. Honda does not specify a minimum.

You can test your wires with a Volt/Ohm Meter. When you do, wiggle the wire around while testing to make sure there are no spikes in resistance caused by dead spots in the carbon core. VOM testing will not flush out bad insulation though. Only the diagnosis steps above will.


Poor maintenance, neglect, incorrect servicing
(use your browser's "Back" button to return to where you were)

Now THIS is one big, BIG, BIG subject, encompassing everything from running out of gas, to old plug wires, to failure to change the engine oil and other fluids, to use of cheap aftermarket parts.

I was going to use this section as a pulpit to excoriate those who would be so irreligious as to generally maintain their vehicle improperly, but thankfully for you I've successfully resisted that impulse.  I've limited my comments to those specific issues that prevent your car from going vroom when you need it to go vroom for you.

So...what sort of neglect/abuse makes your car not start or run?



Low fuel-rail pressure
(use your browser's "Back" button to return to where you were)

Quote from John Ings, founder of this FAQ: "The normal 2-second fuel pump run [when turning the key to ON] is only sufficient to pressurize the fuel rail if it's already full of gas. If the system is empty (you just changed the filter, an injector is leaking, etc.) then it can take a dozen ON/OFF cycles of the key before the rail fills up and the injectors get gas under pressure. By that time, if you've been turning the engine over, the battery is flat!"


Credits
(use your browser's "Back" button to return to where you were)

Some credits are in order here. Some individuals have helped mightily in providing information for these pages. In no particular order are: Jim Yanik, Curly Q Links, remco, motsco, jim beam, Graham W, Kevin McMurtrie, jpoy, Randolph, tomb, Mike Pardee, Matt Davies, KC Casey, (and one person who wishes not to be named, but has been by far the primary source and force behind the igniter pages). Hope I got everybody. Thanks to one and all. Your input makes all this possible.


EFI Main Relay (PGM-FI Main Relay)  back to top of this page    back to Start/Running problems

On older Hondas, this is the most likely cause aside from the ignition switch. Testing and fixing is involved enough that it needs its own pages.

The Main Relay will click three times during the starting process. When problems arise, one of those clicks (usually the third) is missing, making those clicks a handy diagnostics tool.

If you consistently hear/feel all three clicks, the Relay is fine. DO NOT REPLACE IT.

The most common symptom is that you crank, the engine starts, but as soon as you let go of the key, it stalls. If you listen carefully, you'll hear the clicks as they happen. If your ears are poor, or surroundings are noisy, reach behind the dash and put your hands on the relay to feel the clicks. A description of the clicks and when they occur is found under "How does it work?".

Where is the PGM-FI Main Relay and what does it look like?
How does it work?
How does it break?
How can I test it?
How can I fix it? (1) (external link)
How can I fix it? (2)


Bad igniter backto top of this page    back to Start/Running problems

Where is the igniter and what does it look like? (part I) (external link)
Where is the igniter and what does it look like? (part II)
How does it work?
How does it break?
How can I test it?
How do I replace it?



Bad coil
 
back to top of this page    back to Start/Running problems

Where is my coil and what does it look like?
What can cause a coil to fail?
How do I know it's bad?
What does it look like when the coil goes bad?

Honda's ignition system is a very conventional variant of Charles F. Kettering's original design from 1908 (click here to see Kettering's original patent sketch). The coil is charged by current admitted by the igniter (see above). The igniter then breaks the current, and according to laws of physics, an enormous voltage results, which fires the plugs. For more on the Kettering system, Mustang Sally's is the place to go.

What can cause a coil to fail?
In a word, heat.

The old-style cylindrical, oil-filled coils (as mated to Kettering and early electronic systems) would withstand pretty much anything so long as they were protected from vibration. You could easily subject them to the sort of electrical abuse that will kill modern "potted" solid-state coils.

Once the igniter (or points) breaks the current from the battery and 20,000 volts are created on the high-tension side, it cannot simply die where it is. It HAS to go someplace.
Specifically, this means that the high-tension side (or  "secondary side")  of the ignition (rotor, cap, wires and plugs) MUST be in sufficiently good condition to allow that current to travel to the spark plugs and jump the gap there. The entire ignition system and all its parts are designed with no other purpose than to strike an arc across the spark plugs' electrodes, allowing the electrical energy to be dispersed in the sparking action.

Now what happens if the current can't go to the spark plug gap? What if the wires are disconnected or the cap is off? It tries to find a ground someplace else, that's what. It can dissipate into the air or into the oil of an old-style coil, or it can expend its energy heating up its own iron core, or it can try to burrow its way into its own insulation. Any of these things generate heat, and lots of it. The old oil-filled coils would act as heat-sinks, and were able to absorb lots of heat before failing. Modern solid-state coils have far less tolerance for heat, so stranded current is far more likely to overheat and destroy the insulation.

Once the heat has damaged the insulation, the coil is wrecked. Current will tend to follow that path through the damaged insulation even once the proper path has been restored. You can actually see the damage heat can cause if the lighting is juuust right. See a picture here of an excellent pic showing that damage.

Now, having said the paragraphs above, it is true that your coil will withstand brief abuse, such as pulling a plug to test for a misfire. For brief moments the spark can dissipate into the air, o
r leak flux into heating the iron coil core, but continued abuse or poor maintenance will overheat the coil enough that it will eventually die. So keep your "testing" to a minimum!

A common problem is a car that will not start in the wet. Usually that's due to plug wires that are too old. When the wires get old, their insulation begins to break down, and coil current finds a persistent ground through the insulation of the wires. You can wipe them off, and this may improve things, but replacement is the only sure cure. Unfortunately, a proper fix usually involves replacing the entire high-tension side, plugs, wires, cap and rotor, since each part may have had a partial ground established through it. If you replace only one part, you run the risk that current will still be leaking off through another part. And ground CAN be established through ANY part that carries the secondary current, even if it's made of plastic or rubber.

Dirt and carbon tracking inside the distributor cap will have the same grounding effect, preventing current from going where it should, even when the coil is working fine, so check all that before condemning the coil.

The ignition system is a hard-working and finely tuned system that is designed to last many tens of thousands of miles without significant wear. Honda's engineers ensured that all the parts they designed or specified will play nicely together. Parts that are left installed beyond their useful lives will eventually wreck the coil. Aftermarket parts may or may not have build quality or electrical characteristics that are compatible with the rest of the Honda system, and often destroy other components. Such as coils.

Poster J. Poy has recently had an interesting experience with aftermarket parts that appear to have wrecked the coil in a 1991 Integra. More pictures there, so a separate page for that.

With a bad coil, you'll get no spark, just like a bad igniter, or a weak spark.

First thing is to check for spark, to make sure you're not actually getting any. Coils can work fine when cool, but then refuse to work properly when hot. Letting the car cool down wil allow the coil to work again, which is annoyingly similar to igniter failure.

Collected from rec.autos.makers.honda is
How to tell if your coil is bad,
from Rob Relf:
"The simple test to diagnose most no-spark conditions is this:  Connect a dwell meter to the negative coil terminal and to ground.  Crank the engine: No dwell, [likely a] bad igniter; Dwell but no spark, [likely a] bad coil.
"Many coils are ruined by cranking the engine with the cap off or the plug wires disconnected.  The high voltage seeks a path and it is often through the plastic shell of the coil.  Once this path is established it will always want to go that way and results in a spark too weak to start the engine."

If you don't have a dwell meter, an ordinary Radio Shack 12V bulb will do for a test that's also used to check the coil.

Note about paragraphs above: The coil wires do NOT have to be disconnected to perform this test, but:
Never allow the coil to receive power from any source without grounding its high-tension lead!

How do you prevent coil damage and starting problems due to secondary-side parts problems? Maintenance.
Replace all the parts at regular intervals. With OEM.
Cap, rotor, wires: Replace every five years.
Plugs: Replace every two to five years.

If you like, you can listen to the naysayers who say "plug wires last forever", or that "my Brand-X aftermarket parts are just as good as OEM and cost half as much". But just remember, they won't have to help you pay for that damaged coil, or help you troubleshoot a starting problem, or rescue you when you're stranded in the middle of nowhere in a snowstorm...




Ignition switch
 
back to top of this page    back to Start/Running problems

Newer Hondas ('94 and up) are prone to ignition switch failure. Earlier cars are getting old enough that simple wear and age are enough to begin causing problems. If the switch is failing, you may not hear any clicks at all from the Main Relay, and you would mistakenly think it's that. Other symptoms are similar to those of a failing Main Relay. There was a recall on ignition switches for certain years (1997 and up).
Here is the TSB on that recall.

A giveaway for a bad ignition switch is the behavior of the dashboard warning lights when the car stalls, or when the key is first turned to "II". If the switch is bad, the oil, brake, charge and other warning lights will NOT come on. A quick-and-dirty test that is intended to point up a switch that's going bad is this: Turn the key to the start position. As soon as the starter starts to turn, let go of the key, allowing it to snap back to the run position. If the instrument warning lights go out as the switch rotates back, the switch is bad.

The ignition switch actually consists of two parts: 1) The lock cylinder, and 2) the ignition switch itself, installed at the opposite end from the key, and held by two small Phillips screws. The images here are from the factory manual and are for the '91 Integra, but will hopefully be close enough for reference on later vehicles that still have non-chipped keys. Here is a page from the factory manual, showing a diagram of the ignition switch.

Two warnings:

  1. Make sure your "starting problem" isn't actually due to a worn key! Keys do wear, and when they do it can cause all sorts of odd problems that can be easily misdiagnosed as lock/switch problems. At the very least, it's a good idea to get a new key made from a good original master, or order a new one from the dealer before tearing your steering column apart.
  2. A too-heavy keychain can cause the switch to rotate ever so slightly, just enough to kill the power. Try removing the ignition key from your keyring so there's nothing dangling, then see if the stalling still happens. 
If you've already tried these or your key is still good, keep reading...

 
E. Meyer tells how know if your ignition switch is bad:
The surest way is to take it off and pop it open.  The burned contacts are a
dead give away.  It is screwed to the back of the ignition key cylinder with
two small Phillips screws.  The other end of the cable plugs into the fuse
block. 
When it is starting to fail, the "run" contact will overheat and open,
causing the car to stall.  A usual symptom is the dash will also go dark
when it dies (no warning lights, no shift indicator, nothing).  Attempts to
restart usually result in the engine starting and running while you hold the
key in "start" and it immediately shuts down as soon as you release the key.
Wait five or ten minutes for the switch to cool down and it will start and
run normally until the "run" contacts overheat again.  The cycle gets more
frequent as time passes, until it just won't run at all.
Some people have reported they can get it to run for a while by holding the
key between "start" and "run" - try to find the sweet spot where it [the engine] keeps
running, but the starter doesn't.

Kevininiowa has supplied some great data on replacing the switch. He has also included very educational photos of the bad switch itself.
Click here for that page.




How to check the ECU for correct operation
(use your browser's "Back" button to return to where you were)

Just observe the action of the Check Engine light.

When the ECU is behaving normally, the Check Engine light will work this way:

If the Check Engine does EXACTLY what's listed above, the ECU is fine, regardless of whatever other problems you may experience. If the fuel pump fails to run during the two seconds of Check Engine illumination, the PGM-FI Main Relay may be bad.

If the Check Engine light does ANYTHING other than the above, something may be wrong with the ECU.
See here for much, much more detailed info


How to check to see if your timing belt is broken or has slipped
(use your browser's "Back" button to return to where you were)

DO NOT remove the distributor cap to watch the rotor turn. You will destroy your coil. If for some reason you must do this, unplug the distributor's electrical connector block, so power cannot reach the coil.

To check for belt breakage, remove the oil filler cap, and either turn the engine over by hand with a wrench, or crank the starter. If you look down the oil filler hole, you'll be able to see the camshaft. If the belt is still whole, the camshaft will turn when you turn the crankshaft. Watch your clothes, oil may splatter.

Much more common than actual belt breakage is slippage, where the belt jumps a tooth. For this you will need a timing light. Since the distributor is mounted to the camshaft, any belt slippage will manifest as severely mistimed ignition. Normally, when cranking, ignition should be slightly retarded from the normal position but still before TDC. If the belt jumps a tooth, timing will be after TDC.

If the timing is extremely far off, it is possible for the valves to hit the pistons and get bent, which means a head off repair. If you suspect that this is the case, check the valve clearances. If one or more is much, much bigger than spec, a bent valve is likely.



How to check for spark
(use your browser's "Back" button to return to where you were)

Spark problems make up almost 90% of starting/running problems. Luckily, it's very, very easy (falling-off-a-log easy) to check to see if you have spark. Unfortunately, any checks kind of require that you have a helper to turn the ignition key while you watch what happens at plug level. WARNING: Never crank the engine with the plug wires removed and ungrounded, or with the distributor cap off and ungrounded, except for brief (very brief) testing purposes. Doing so can overheat and damage the ignition coil. This test grounds the spark plug, and ungrounded intervals are short, so you're OK here.

A good spark is blue or yellow. A bad one is orange to red. However... it depends on how you checked it. Keep reading.

It's always best to check for spark in a dark area, like a garage with the lights off, or at night. The darker the better. At night, a good spark will be purply-blue with the normal spark plug gap. In daylight it may be difficult to see at all, but you'll sure feel it!

To start, you'll need a spare spark plug. Go to your favorite auto parts emporium and buy a spark plug. Any plug that fits your car. In this case, you can throw any quality concerns happily out the window and buy the cheapest thingy that fits your motor. All you need is something to stick into the plug wire you pull off your installed spark plug. If it will convey a spark, that's all you need. Actually, even any old, used (but not too used) plug you may have lying around will do as well.


Bend ground electrode so gap is very big Some suggest bending the plug's electrode so as to increase the gap to make the spark easier to see. This is OPTIONAL, but does help when attempting to see the spark in bright daylight.

You don't have to increase the plug gap to see the spark, If you bend the gap so as to open it up (like in the picture) to make the spark easier to see in daylight, the spark will be more visible, but will also be yellower in color. If you see a yellow spark with the big gap, don't panic. The bigger the gap, the yellower the spark.

Using loose plug to force spark to jump Now take your plug and install it into the nearest convenient plug wire, which has necessarily been disconnected from its normal plug.

Touch the assembly to a convenient ground so the current has somewhere to go once it jumps the gap. Here I'm using a valve cover hold-down nut.


If you do this with the engine running, you will receive shocks as you insert the new plug and hold it to the valve cover nut. Once you touch the plug to the nut, the shocks will stop. They hurt, but do no harm! Unless you have certain medical conditions, I guess.

Checking for spark with no plug
Alternatively, if you wish not to use a spare spark plug or can't get hold of one where you are, you can simply hold the spark plug cable end close to an engine ground and have your helper crank the starter. (Don't worry; no damage will result from this short-term test of only a few seconds.)

Hold the plug wire as close as you can to the hold-down nut or other grounded object, but make sure you're still able to see the spark's arc. The spark will have to jump a very large gap with this method (over an inch), so it won't be purply blue, but will be a deep yellow.

If there's no spark at all, or it's intermittent, or red and very quiet, then you've got a spark that may be too weak to start the engine.

A bad battery or starter can cause a weak spark. The starter ends up drawing so much current in an attempt to turn that there's not much left for the ignition system. The dome light test will help find that out.

If you see the correct spark appearance, and you see it at all plug wires, then your spark is fine.


Yet one more way to check for spark (although this one will tell you nothing about the quality of the spark):
If you have an inductive timing light, simply clip the pickup to each plug wire in turn and see if the light flashes. If it does, you've at least got some kind of power coursing through there, which ought to be enough to help the car start.


How to check for fuel
(use your browser's "Back" button to return to where you were)

Firstly, let's restate: 90% of starting problems have to do with the ignition. Go make 100% certain that's OK before you play any sort of blame-game against the fuel side.

Secondly, fuel delivery trouble is usually flagged by a Check Engine light (MIL) and an ECU/ECM error code. Injector non-function is usually the PGM-FI Main Relay. If the Main Relay malfunctions, either the fuel pump won't run or the injectors will not receive power.

Checking for fuel with a carbureted car or an older car with throttle-body (dual-point) injection:
(First, do make sure the engine isn't flooded...)

Iit's easy to see if fuel is being delivered. Just peek inside the throttle body while you crank. Gas ought to be being visibly sprayed into the throttle body. If no gas is present at all, you've got a no-fuel situation. Sorry to sound obvious, but do check to see if there is actually gas in the gas tank. You'd be amazed how many people run out of gas and figure there must be something wrong with their car.

If you definitely see no fuel being delivered, put some gas into a small cup, and pour it very slowly into the throttle body as you crank. If the car now starts, you know for sure gas isn't getting to the carb/throttle body.

If this is a carbureted vehicle, make sure you're holding the choke plate open (at the very top of the air horn) with your fingers, then pump the throttle crank and see if the accelerator pump is delivering a shot of gas. If it's not, there's a problem.

The opposite can happen too, where too much gas is sprayed in. You'll recognize this by the fact that gas is literally dancing on the brass-colored throttle plate and is dripping off the edges. The exhaust will smell weird, idle will be high, and your gas mileage will be terrible.


Checking for fuel delivery to multi-port injected vehicles (no injector in the throttle body):
(First, do make sure the engine isn't flooded...)

If you have a good spark, but suspect that fuel is not being delivered, get a can of Starting Fluid from your favorite auto parts emporium. With the air hose disconnected from the throttle body, and with the throttle plate held part-way open either by hand or by your helper pressing the gas pedal part-way, spray starting fluid into the throttle body while cranking. If it now starts, you have a fuel delivery problem.

Fuel is delivered to the injectors via the fuel pump. In order to achieve the correct spray pattern at the injectors, it has to hit the injectors at the correct pressure. That means the fuel pump must run (of course), and must pressurize the system to its operating pressure (roughly 35-40 psi). A fuel pump in good shape is capable of sending far more fuel to the engine than it will ever need. The pressure itself is controlled by the regulator, which bleeds off excess gas back to the tank  to prevent the system from over-delivering fuel.

The sequence is this (for return systems):
  1. Pump operates;
  2. Fuel passes through the pump check valve;
  3. Fuel goes through lines to the filter;
  4. Fuel passes through filter, past the pulsation damper into the fuel rail;
  5. Fuel that's needed sprays through the injectors as the ECM operates them;
  6. Excess fuel passes through the pressure regulator and is returned to the fuel tank;
  7. Repeat from #1.
(Returnless systems have the pressure regulator in the fuel tank, so excess fuel is returned to the tank before it even leaves it.)


What to check, in order, from the tank up to the engine:
Anything that goes wrong with any part of the fuel system will result in delivery problems.
Start with the pump, and continue downstream. You can do the following steps backwards, if you like, from fuel pressure regulator back to the pump. Your choice.

Pump: Is it running? When you first turn the key to II (ON), the ECM and Main Relay cause the pump to run for two seconds.  If you listen very carefully, you can hear it hum while the Check Engine light is on. A fuel pressure gauge will tell you for sure if the pump is generating correct pressure. It's plumbed into the service bolt hole that located on top of the fuel filter's outlet. If you haven't got a gauge, clean off the service bolt, loosen it one turn and see if fuel seeps out (have a rag handy). If it does, at least some fuel pressure's getting through the filter. But is it enough? Only a gauge will tell you for sure, but there are some things you can try further on in this article... Fuel filter connections

Pump check valve: The fuel pump check valve is supposed to keep the pressure from draining back to the tank when the car is shut off. If it happens to stick, pressure will bleed down and the pump will have to work to boost it back up again. Turn the key from  0 (OFF) to II (ON) a dozen times in a row (leaving it in II until the Check Engine light goes off) will compensate for any problems with the check valve. If the car now starts, the check valve becomes one of your suspects.
In case you were wondering, the pump runs at all times while the engine is running.

Filter: Crud can build up in the fuel filter, especially if the fuel tank is regularly kept at a low level. Water can enter the lines and freeze in the winter, blocking things solid. If you have no fuel pressure gauge and are unsure of the age of the filter, replace it.

Fuel rail: If you've discovered fuel's getting past the filter, it's time to look further downstream. checking the fuel rail itself is difficult without removing it. However, you can remove a spark plug
(make sure the wire is grounded to the engine or chassis so as not to cause damage to the coil!! or pull the ignition fuse), then crank the engine over. If fuel is being delivered, you may see (or smell) it being sprayed out of the spark plug hole as you crank. If there's no gas smell at all, then you know no gas is present at the injectors. Even if there is gas, there may not be enough to fire the engine up.
Note: If you've just replaced the filter, or have run out of gas, it may take up to a dozen key on-off cycles as outlined above to boost fuel pressure back to the correct level.

Injectors: Not really possible to check these by eye without pulling the fuel rail. Generally speaking though, faulty injectors are not likely to cause a no-start, but more likely to cause driveability problems once the car's running. If the injectors are not actually functioning, they won't make a click noise, and this can be determined with a mechanic's stethoscope, or it may be felt with the fingers, as the engine is cranked
. I've been told that at least some ECMs will refuse to pulse the injectors unless they see an ignition event. This would mean an ignition failure would lead to no fuel, a bit of a chicken-and-egg situation.
If you suspect your driveability problems are due to dirty injectors, running a can of Chevron Techron additive to a tank of gas might help, as may a Motorvac service. If Techron isn't available in stores in your area, you can try a few tanks of super-premium gas, which may have more detergents than your regular fuel (or so I'm told). These things will also help reduce heavy valve-face deposits, also a cause of driveability problems.


Pressure regulator: This device can freeze with water and plug up. Its spring can get weak, allowing too much fuel to return to the tank too quickly, presenting too little fuel pressure to the injectors. If all your previous checks turn up no problems, do two things:
1) Disconnect the return hose from the regulator, and place a length of spare fuel hose from the the regulator's outlet to a jar. Now crank. Is fuel shooting into the jar? Then the regulator is at least passing fuel. But is it passing enough? Step 2 will help determine...
2) If you suspect too low pressure, get a pair of pliers, and pinch the return hose shut with them. This will force injector pressure higher by preventing a weak regulator from bleeding off pressure.
3) A perforated diaphragm will result in aflood of fuel into the intake manifold through the regulator's vacuum line. Pull the lne and check for a strong fuel smell, or perhaps even liquid gas.
Fuel pressure regulator

And  a final gotcha, just to keep you on your toes: I encountered an odd one recently: An owner had replaced his fuel pump and the car wouldn't start. The Check Engine light wasn't coming on, but no fuel was getting to the injectors. The car started with a spray of starting fluid. It turned out he had managed to swap the fuel lines around. This meant the pump was sending fuel down the low pressure return line instead of through the proper high pressure line to the fuel filter. According to him, the fuel was getting as far as the regulator, but not to the injectors, as the regulator wasn't letting it pass to the injectors. Changing the connections back fixed that. I'm not sure how this could happen, but that's what he reported to me.