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Old 09-04-2006, 04:51 PM
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nwebie needs help calling techs

Hi all,

I have a 95 elf buss with a 7.3 my problem is that I am loosing the fdcs(fuel deliverly command singal) interminttaly and the injector PW goes to .6 a no fuel command and runs really rough.From what i understand it gets it through the pcm from crank sensor.i have a new crank sensor in it and I know there are 3 different types so I ran the vin and got correct 1 from ford.the only thing i see is when i watch the singal pattern it goes strait up and acroos but goes alittle zigzag at top coner befor comming down all else is fine with patterent shows tdc.I have pinned all wiring and resistance is good,tried new PCM and IDM didn't make a difference, dodne injector buzz test all fine.Just wondering if anyonelse came acroos this or has any suggestions any help you can give me would be appericated.

Thanks
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Old 09-04-2006, 05:09 PM
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Sounds like the same thing that happened to mine, change the valve cover gaskets they control the injectors, the wiring inside the valve cover melts and causes a dead miss that is horrible, it will run but it runs very rough right? The wiring harness that plugs into them on the inside of each valve cover there should be one on the front as well as on the back and if I remember correctly the gaskets were somewhere around 100 dollars each and the plugs werent cheap either. Let me know if this is the same problem you have.
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Old 09-04-2006, 05:18 PM
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i would definately pull the valve covers next and inspect the connectors. The obs motors have four, two on each cover.....and they do sometimes burn a pin and go intermittant....
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Old 09-04-2006, 06:01 PM
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thanks mark for clearing up the termanology that is necessary for this problem but I do think that it is very possible that this is his problem.
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Old 09-04-2006, 06:03 PM
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Quote:
Originally Posted by chancelor View Post
thanks mark for clearing up the termanology that is necessary for this problem but I do think that it is very possible that this is his problem.
I agree with ya, sometimes its just "make it a little simpleer" to make it read better...lol
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Old 09-04-2006, 06:36 PM
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I don't think its in the valve cover harness I have checked all wiring in the system from PCM to IDM to all sensors,injectors,glow plugs and through all harnesses the resistance is all ok and no shorts to ground.The problem I have is the injector plusewidth(injector on time) usally should be about 2.3 milliseconds while running but it drops to 0.6 wich is a no fuel command from the PCM then it runs rough. It does it intermintally runs good for 10 min then rough for a while and sometimes runs good for only 30 sec and then rough it does it cold or at normal operating tempature All other sensor data is normal.i cant figure out why the PCM is sending a no fuel command.I have tried 3 PCM all the same and 2 IDM.
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Old 09-05-2006, 03:47 PM
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Is the signal from the MAP good? There may be an intermittant fault in it making the truck defuel.
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Old 09-05-2006, 05:33 PM
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I'm not a tech by any means but it seems to me that if you tried 3 PCM's with the same result, i would start looking at inputs. What does the PCM use to determine pulse width modulation????
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