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  #1  
Old 09-12-2011, 01:28 AM
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Default CEL not clearing, suggestions?

I have a 95 civic ex and I can't get the CEL to clear. I've been trying to troubleshoot a cranking but no starting issue and i think I've narrowed it down to the fuel pump not working. I've tried the jumper wire trick to get a trouble code but that doesn't work. Then I removed the fuse to clear the code and left it out for a good 30 min, all with the neg battery cable disconnected but the CEL still lights up and stays lit as soon as I plug everything back on and try to turn it over. Plus, I still can't get it to flash a code anyway. Any suggestions? I'm guessing the worst case is a bad ECU, and i'm hoping that's not the case. thanks for your help.
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  #2  
Old 09-12-2011, 01:42 AM
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The main relay is a common problem and it will do exactly that-- cranks but won't start, fuel pump doesn't run, and CEL stays on rather than going out after 2 seconds with key on but don't crank.

So it's a safe bet to resolder or replace the main relay.

You could also check the ECU grounds on the thermostat, and test if the spark plugs fire. With a bad main relay but everything else OK, the spark plugs will fire, but engine won't start due to lack of fuel.

Last edited by mk378; 09-12-2011 at 01:45 AM.
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  #3  
Old 09-12-2011, 10:59 AM
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I pulled the main relay out and looked for any cracks in the solder joints but i'll resolder it today and see if that fixes it. I suppose the solder joints could just be 'dry'. thanks for the suggestion. will report back when done.
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  #4  
Old 09-12-2011, 09:12 PM
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Ok, so I resoldered the main relay, and then tested it with different source of power. The relay works under the test, i can even hear it click. then I hooked up the jumper to the relay housing to test if there was power getting to the fuel pump, and there's no power getting to the pump. then I tested to see if there's even power getting to the relay, and had no luck. So, that leads me to believe that it's not the fuel pump nor the relay, but perhaps the ECU itself. there was an electrical fire that caused the whole thing with the speed sensor so I'm assuming that could have fried the ECU. I already replaced the main wiring harness and the speed sensor. I just want this car to start!!! So, would I be correct in assuming that it's probably the ECU? Just want to have some verification before I order one, and it's not like you can return them on ebay. Suggestions welcome and appreciated!
thanks,
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  #5  
Old 09-13-2011, 07:19 AM
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Oh, OK-- finally you mention that the car being ON FIRE is what led to this no-start situation.

Likely there is a wiring problem and no power to the ECU. Do the "oil" and "battery" lights on the dash come on when you turn the key on? Do the spark plugs fire? Do you have 12 volts at the yellow-black wire on the distributor with the key on? Look at a wiring diagram, there are about 3 pins on the ECU that must receive power (from different sources) before it will run. Also of course check those grounds on the thermostat.
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Old 09-13-2011, 04:40 PM
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The oil and battery lights come on when key is turned to 'on' position. I haven't checked the others yet, the car is about 30miles away and I don't know if i'll get back to it before friday. the car turns over, but does not start. I know I should have checked to see if there was spark, but thought that since there is no power getting to the fuel pump that it must be an ecu issue, especially after i tested the main relay and found it to be working. If no power is getting to the ECU, would the CEL even come on at all? is it not the ECU that puts out the lights and codes? But i'm assuming that if not all three pins are receiving power then it could give false readings. I replaced the entire main wiring harness as well. I'll check the other points when I get over there next. I guess I should wait to order a new ECU until those others are checked? Although I would imagine that a short from a fire might require replacing it anyway..
thanks again..
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  #7  
Old 09-14-2011, 04:48 AM
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Bad ECU's are rare so you should check everything else first. The ECU processes spark as well as fuel. It receives pulses from the distributor sensors, re-times them, and sends pulses back to the igniter module (which is inside the distributor, it's also called the ICM) to fire the coil. If sparks are firing, you can be somewhat confident the ECU is good.

Other tests you can do are check for 5 volt power at the MAP and TPS, it is supplied from a voltage regulator inside the ECU. Having this wire shorted to ground will probably disable the ECU for as long as the short exists, but not permanently burn it out.

Disconnect the solenoid wire at the starter so the starter won't turn. Since you know it won't start anyway, this is to save wear on the starter and battery and so you can hear the fuel pump. Next press the clutch and turn the key to the start position-- the fuel pump should run continuously. (I think that will happen even with no ECU participation, as there is a bypass from the starter circuit straight to the main relay, but would have to check diagram to be sure) Also with the key turned to start check for power to the distributor and fuel injectors.

And double check those ground wires on the thermostat housing, it is so easy to forget them during an engine swap or re-wiring job.

Last edited by mk378; 09-14-2011 at 05:00 AM.
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Old 10-05-2011, 01:27 PM
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Ok, so here's an update. I did some more testing, and have found that I'm not getting any spark. So, I tested the ICM and the ignition coil per specs in the Haynes manual and they all tested ok. I also replaced the ECU just to see if that may have helped, with no results. I checked the ground wires on the thermostat housing and the ground is good. For some reason I don't trust the tests on the ignition coil and ICM because it makes no sense that those would test fine, yet get no spark through the cap and wires to the plugs. And even if it was something as simple as the distributor cap, that still would not explain why there is no power getting to the main fuel relay and consequently the fuel pump. I'm stumped. any other suggestions? I guess i could just get a new icm and see if that's it? if not, return that and do the same with the coil?
-Frustrating.....
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  #9  
Old 10-05-2011, 01:56 PM
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so I just tested for power to the MAP and TPS and got only .2 volts for both with the ignition set to ON.
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  #10  
Old 10-05-2011, 03:15 PM
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Did you ever check for power to the distributor? Power for the MAP and TPS comes from the ECU, which in turn comes from one of the power circuits I think the one from the section of the main relay that doesn't run the fuel pump. The fuel injectors should also have 12 volts on both wires with the key on and engine not running. Sounds like an open circuit in the car wiring somewhere.
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Old 10-05-2011, 03:15 PM
 
 
 
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14, 95, cel, civic, clearing, code, fuel, honda, icm, main, plug, pump, relay, start, working

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