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89 Cutlass No Start


Rodger E.'s Avatar
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10-05-03, 04:34 PM   #1  
Rodger E.
89 Cutlass No Start

89 Cutlass Supreme; 2.8 V6; Auto Trans

I posted on this problem a couple months ago. People here were kind enough to send schematics which I've referred to for my diagnosis.
The car won't start because the fuel injectors are not firing. Ignition is fine. I have an Actron Fuel Injection Testor which I can check the fuel injector harnesses, the fuel injector inself, and I can fire the injectors remotely with the unit. With the use of this unit I have determined that the injectors are good; the harnesses are good, but the injectors are not recieving a signal to fire. I have checked all fuses, relays relating to the fuel injection system. I am getting over 40 psi fuel pressure. I have manually gone over the harness, even though the testor determined it was good, and found nothing wrong. When I use the Actron testor to fire the injector manually, the engine will fire. (It will not start though, because I can only fire one injector at a time.) I have tried a new computor, but I get exactly the same problem. If I spray gasoline into the intake while turning it over, it immediatly starts up. Does anyone have any more ideas?

 
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YamahaWolverine's Avatar
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10-05-03, 04:50 PM   #2  
Start with a test light. See if you have power at either side of each injector connector. If ok install the test light in series and crank the engine. See if the light flashes. Let us know what happens from there.

 
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10-05-03, 05:36 PM   #3  
Joe_F
Sounds like you have a ground problem. Check your wiring/grounds again.

 
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10-05-03, 05:39 PM   #4  
That was a great symptom description. It really is refreshing to hear from someone who has done his homework

My thinking is clearly that a sensor is faulty, thus the computer does not know it is time to fire an injector. I can only think of one sensor that could allow the plugs to fire without the injector receiving the twin signal.

If the TPS (throttle position sensor) is faulty, it could cause this problem. The reason for this is that at WOT (wide open throttle, detected by the TPS) during starts, the computer will not fire the injectors intentionally. Perhaps your TPS is shorted in such a way as to imitate this condition?

On difficult problems like this, I am reminded that often we can't see the problem because we have previously incorrectly eliminated it. In other words, reconsider the validity of all your test results so far. For example, be sure you are getting 40psi fuel pressure on the injector side of the fuel regulator, etc.

Lugnut

 
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10-05-03, 07:24 PM   #5  
mike from nj
the next step for me would be to 'ohm' the wires from the injector harness to the computer.

injectors receive power from a fuse or two, the computer grounds the other wire to fire them, very simple system.

if you have consistent spark on all the wires, then you can assume the crank sensor is functioning

 
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10-05-03, 07:40 PM   #6  
you should check everything that everyone has posted as any of those things could cause the problem that you describe and you also should check the ignition module as it can also cause no injector pulse and still have fire.

 
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10-05-03, 07:50 PM   #7  
mike from nj
you're right BJ, the crank sensor is hard wired directly to the ignition module, then through the ignition module to the computer, i forgot about that.

never assume!

 
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10-06-03, 07:15 AM   #8  
U SHOULD HAVE A GOOD SUPPLY OF POSITIVE BATTERY ON ONE SIDE OF THE INJECTOR. IF THAT IS GOOD, CHANCES ARE THE IGNITION MODULE IS NOT SENDING THE ENGINE SPEED SIGNAL TO THE ECM, BUT IT IS MAKING SPARK BELOW THE THRESHOLD WHEN THE ECM TAKES OVER.

 
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10-06-03, 09:54 AM   #9  
Rodger E.
Thanks everyone for the replies. Some very good info me for me to look into and learn from.
Where is the ignition module located on this vehicle? It has a distributorless ignition and I know where the three coils are located on the side of the block.

 
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10-06-03, 10:16 AM   #10  
Joe_F
The module is under those coils you describe.

 
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10-11-03, 03:51 PM   #11  
Rodger E.
I still have the same problem but discovered something else. The fuel pump will not come on when the key is turned on for a few seconds which it is supposed to do. The fuel pump will run using the test lead at the fuel pump control relay and will produce almost 50 psi. Using a service manaul, I went thru the entire fuel pump flow chart diagnosis and it comes up telling me that the PCM is faulty. I also checked continuity and connections on the wires relating to the fuel pump, relay, and it connection at the PCM. I've jumpered the fuel pump at the test connector and tried starting the engine but still no firing of the injectors.
Can the fuel pump not running when the key is turned on, or when cranking the engine cause the injectors not to fire? (When I ground the injectors manually, I can hear them click)
I have installed a known to be good PCM, but no difference.
As recommended by Yamahawolverine, I checked with a test light at the injectors and they have power. As I diagnosed previously, the injectors don't get a pulse when I put the test light in series with the harness and injector.
I have installed another ignition module and coil assembly that is known to be good, but no difference.
I get strong spark from each plug wire which indicates that the crank sensor is functioning.
I have checked the throttle position sensor and it has a smooth voltage transition throughout the entire rotation.
So the mystery goes on. If anyone has any more ideas or sees a flaw in my diagnosis, I'll welcome your reply.
Thanks, Rodger

 
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10-11-03, 06:09 PM   #12  
".... (When I ground the injectors manually, I can hear them click)..."
Does that suggest that you have a ground problem?

 
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10-11-03, 06:26 PM   #13  
Joe_F
Yes, I would agree you still have a ground issue.

 
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10-11-03, 06:58 PM   #14  
should note that not all test lights are capable of telling you wether or not you have injector pulse the proper light to use would be a noid light as some test lights will not light on the small pulse it recieves from pcm.
if you have a schematic for the ecm look for your grounds and powers wires for the ecm and to check both the power wires and ground wires at the ecm connectors with ecm unplugged using a headlamp that you make into a test light the reason for using a headlamp is to put enough amperage through the wire to indicate if it is bad that may normally wouldnt show up using a test light or ohm meter.

 
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10-11-03, 07:54 PM   #15  
Rodger E.
What about the fuel pump not running when the key is turned or while cranking the engine? Does that have anything to do with the injectors not firing or do you think that is also a ground issue?

 
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10-11-03, 08:14 PM   #16  
both the fuel pump relay and the injectors are grounded by the ecm so if the ecm is lacking a power or ground it could be related that is the only way it would be related.
in your first post you stated you had 40 psi pressure now im assuming you dont have none unless you power up the fuel pump using a jumper wire which seems a little odd that you used to have pressure now you dont perhaps one of the parts you changed is faulty.

 
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10-12-03, 12:59 PM   #17  
Rodger E.
Yes, in my initial post I stated that I had 40+psi fuel pressure but that was measured when I put 12v to the test lead at the pump relay. I don't believe that the fuel pump was running when the key was turned back then either, being that I don't remember hearing the pump run. Since then, I've aquired a service manual therefore enabling me to perform the diagnostics printed in the book.
Thanks everyone for plugging along with me on this. I'm going to continue trying to find grounding problems but if anyone has more ideas, feel free to post.
Thanks again, Rodger

 
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