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Diesel Mafia #67
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Discussion Starter #1
A buddy of mine has a 99 If you hop in the truck (desnt mater how cold it is..) IT wont fire... all it does is try and try.... cycle the key it fires right up.....

Or you can just cycle the key twice and if fires up... his pumps took a crap on him so we replaced them and it still does it... Its not hurting anything I was just wondering WHY his does it but no other one I know does it..?
 

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Professional Grouch
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A buddy of mine has a 99 If you hop in the truck (desnt mater how cold it is..) IT wont fire... all it does is try and try.... cycle the key it fires right up.....

Or you can just cycle the key twice and if fires up... his pumps took a crap on him so we replaced them and it still does it... Its not hurting anything I was just wondering WHY his does it but no other one I know does it..?

Could be a grid heater issue but doesn't sound like it. Cycling the key on and off as you describe may be commanding the ECM into CEL/malfunction code analysis which could conceivably come into play here but I am doubtful of this as well. How fast is your friend cycling the key switch and in what fashion.

If he is cycling the key switch twice and each time he turns the key to the on position he waits for the wait to start light to go out and does this twice, it would stand to logic and reason that it does start especially when it is very cold out and the engine is cold. The grid heaters are operated by the ECM with senses intake air temp via the IAT sensor. When the IAT sensor senses less than approx. 60 degrees F; the grid heaters are commanded to active prior to each start attemp, and cycle on and off until intake air temp as sensed by the IAT sensor is approx. 60 F.

Is that clear as mud? The Cummin 5.9 B series engine does not employ glow plugs, they use a grid heater system.
 
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Diesel Mafia #67
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11,283 Posts
Discussion Starter #5
Could be a grid heater issue but doesn't sound like it. Cycling the key on and off as you describe may be commanding the ECM into CEL/malfunction code analysis which could conceivably come into play here but I am doubtful of this as well. How fast is your friend cycling the key switch and in what fashion.

If he is cycling the key switch twice and each time he turns the key to the on position he waits for the wait to start light to go out and does this twice, it would stand to logic and reason that it does start especially when it is very cold out and the engine is cold. The grid heaters are operated by the ECM with senses intake air temp via the IAT sensor. When the IAT sensor senses less than approx. 60 degrees F; the grid heaters are commanded to active prior to each start attemp, and cycle on and off until intake air temp as sensed by the IAT sensor is approx. 60 F.

Is that clear as mud? The Cummin 5.9 B series engine does not employ glow plugs, they use a grid heater system.

I left some thing out.. IF you DONT wait to start... itwont start.. if you wait.... start...... cycle the key again waiting...... it fires right up.... It does this weather its hot or cold( motor) you could driv it for an hour strait and walk into the gas station, an you would have to cycle the key...

So you think it could be the IAT?
 
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