HELP!!!...95 SL1 sedan no fuel going in cylinder #3

[donrob42]

I really need your help guys on this one. I have a 1995 Saturn SL1 4 door 5-speed sedan with 130k miles. The car has been well maintained over the years. Yesterday I noticed hearing the engine missing so the first thought was I had dropped a cylinder or had a burnt valve. I did a compression test on all 4 cylinders and to my surprise I got 150 psi on all four cylinders. I then tested the coils, ignition module, spark plugs, and spark plug wires. I even tested the fuel injector electric plugs with my multimeter on all four plugs to make sure I was getting voltage to all lines and it was getting 10.4 volts on each. All those other things checked out fine. I then said it have to be a bad fuel injector for cylinder #3 so I went out and purchased a new fuel injector and installed it. Still, the car is missing on cylinder #3. The bottom line on this is the engine starts right up but for some reason injector #3 is not spraying fuel into the cylinder. There are no check engine light but cylinder 3 is not getting fuel. Its getting great spark but no fuel. Does anyone know why the injector is not spraying fuel into cylinder 3? Is there any other componet that needs to be replaced that tells the fuel injector to spray?

P.S. There is a green plug-in at the end of the fuel injector harness lines that plugs into a little square box on the opposite end of the throttle body. Im not sure what that little box is for but it is connected to the fuel injector harness wires. Could that cause this problem?? I really need your help on this guys because I have done everything that I know to do to get fuel to that cylinder with no luck.

[fdryer]

1-Fuel injectors should have 12v on either wire to each injector. The pcm switches ground to pulse each injector on/off.

2-Is this green plug connected to the throttle position sensor or not? The tps is opposite the throttle lever/cable and should have an electrical connection to the harness. No connection means the pcm has no idea of throttle position.

3-What's the fuel pressure? Measure it with a fuel pressure gauge as guessing is not an option at this point in troubleshooting. Maybe Autozone has one for loan?

[donrob42]

Originally Posted by fdryer

1-Fuel injectors should have 12v on either wire to each injector. The pcm switches ground to pulse each injector on/off.

2-Is this green plug connected to the throttle position sensor or not? The tps is opposite the throttle lever/cable and should have an electrical connection to the harness. No connection means the pcm has no idea of throttle position.

3-What's the fuel pressure? Measure it with a fuel pressure gauge as guessing is not an option at this point in troubleshooting. Maybe Autozone has one for loan?

The TPS plug is connected to the TPS....the plug I was referring too is the green plug that feeds off the end of the fuel injector wiring harness. It plugs into the bottom of that small square box that is positioned at the opposite end of where the throttle body is (passenger side of the engine compartment). Im not sure about fuel pressure?? The car starts right up and runs and there is no check engine light but no fuel is going to cylinder 3.

[donrob42]

What componet controls and tells the fuel injectors to work? Im think that may be my problem??

[madpogue]

The PCM fires the injectors by grounding them, as said above. If the engine is running, the odds of a PCM failure are millions to one. Most likely it's the switched ground wire between that injector and the PCM.

Did you have the throttle wide open when you did that compression test? All plugs out? Fairly warm engine? Fully charged battery? If so, the compression is below the service limit of 180 psi.

[donrob42]

Originally Posted by madpogue

The PCM fires the injectors by grounding them, as said above. If the engine is running, the odds of a PCM failure are millions to one. Most likely it's the switched ground wire between that injector and the PCM.

Did you have the throttle wide open when you did that compression test? All plugs out? Fairly warm engine? Fully charged battery? If so, the compression is below the service limit of 180 psi.

To see if that #3 injector was working, I disconnected the fuel rail from the the back of the head with all fuel injectors still in the fuel rail. I disconnected the fuel injector harness from all injectors except the #3 cylinder. I had someone turn the key as I watched the fuel injector and it is spraying a mist of fuel on and off as it is suppose to do....I just cant figure out why that cylinder is missing once I put everything back together?? Good Spark, Good Compression, but it just isnt any fuel going to that cylinder to be burn. Is it possible for something to be blocking the fuel from going into the cylinder since I know the injector is working by seeing it function??

[td1238]

Could you perhaps have a bad intake or exhaust lifter? I'm not sure how this would affect compression. I'm guessing that it might lower it, as it would restrict the intake of air. If the exhaust were failed, this wouldn't restrict the intake of air, so it wouldn't likely affect compression numbers, but it would prevent the expulsion of exhaust gasses, and would probably destroy combustion during actual operation.

What makes you think that the #3 cylinder is misfiring? Does the plug look different than the rest. Is there no change when the plug or injector for #3 is disconnected?

150psi is low, but the engine should run.

Are you sure that you have the plugs connected properly? Should be 4,1,2,3.

[donrob42]

Originally Posted by td1238

Could you perhaps have a bad intake or exhaust lifter? I'm not sure how this would affect compression. I'm guessing that it might lower it, as it would restrict the intake of air. If the exhaust were failed, this wouldn't restrict the intake of air, so it wouldn't likely affect compression numbers, but it would prevent the expulsion of exhaust gasses, and would probably destroy combustion during actual operation.

What makes you think that the #3 cylinder is misfiring? Does the plug look different than the rest. Is there no change when the plug or injector for #3 is disconnected?

150psi is low, but the engine should run.

Are you sure that you have the plugs connected properly? Should be 4,1,2,3.

Spark plug wires are in correct order and the engine isnt effected when I pull the #3 wire off. I have great spark and good compression, but cylinder not getting fuel.

[fdryer]

Originally Posted by donrob42

To see if that #3 injector was working, I disconnected the fuel rail from the the back of the head with all fuel injectors still in the fuel rail. I disconnected the fuel injector harness from all injectors except the #3 cylinder. I had someone turn the key as I watched the fuel injector and it is spraying a mist of fuel on and off as it is suppose to do....I just cant figure out why that cylinder is missing once I put everything back together?? Good Spark, Good Compression, but it just isnt any fuel going to that cylinder to be burn. Is it possible for something to be blocking the fuel from going into the cylinder since I know the injector is working by seeing it function??

Turn the key to ON or START? What did the other injectors do when the ignition switch was turned ON? START?

[donrob42]

Originally Posted by fdryer

Turn the key to ON or START? What did the other injectors do when the ignition switch was turned ON? START?

I un pluged all of the injectors except for cylinder number 3 and tested it individually since it was the only cylinder not working. I could see a mist of fuel spraying from the injector. But as I stated for some reason when I plug everything up cylinder number 3 does not get fuel.

[fdryer]

One more time. Turn the key to ON or START? What did the other injectors do when the ignition switch was turned ON? START?

If I recall correctly, injectors do not spray until the engine is turned over. Simply turning ON the ignition should not have any injector spraying at all. If you insist on dwelling on just injector #3 without testing or assessing how the other three injectors work will tend to give you tunnel vision.

[donrob42]

Originally Posted by fdryer

One more time. Turn the key to ON or START? What did the other injectors do when the ignition switch was turned ON? START?

If I recall correctly, injectors do not spray until the engine is turned over. Simply turning ON the ignition should not have any injector spraying at all. If you insist on dwelling on just injector #3 without testing or assessing how the other three injectors work will tend to give you tunnel vision.

I did have someone spin the car over while I observed the injector spraying. The only reason I didnt check the other three injectors is because #1, 2, and 4 are working perfect when the engine is running. The only cylinder that doesnt idle down when I pull the spark plug wire of the spark plug is cylinder #3.

[td1238]

Observe all injectors and compare.

Might also be a good idea to remove the valve cover and observe the valves while turning the engine over slowly, either with the crank motor or with a socket (do not leave socket on engine while cranking electrically).

Make sure that exhaust valves open and close.

[td1238]

Also try moving spark plugs around, or try a new set of wires. Perhaps one of the plugs is shorting out under high tension (perhaps there is a fine crack that you can't see, etc.).

Try swapping ignition coils. Maybe one of the coil terminals is shorting or arcing to ground.