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yurkym
Joined: 15 Apr 2006
Posts: 18
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| Posted: Tue Jan 02, 2007 6:24 pm Post subject: why loss of power |
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| When we start the truck lately, when shes cold, the speedometer wont register and it will only tach to 1600. This has just started recently and after a while it will kick on. We have a n14 Cummins. Any ideas |
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marylandkw
Joined: 06 Sep 2005
Posts: 474
Location: Maryland
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| Posted: Tue Jan 02, 2007 8:02 pm Post subject: |
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This is an easy fix.......Get rid of your Cummins and get a nice big yellow motor. :lol: :lol:
I had this problem a few years back, was interment at first and then became steady after about 300 miles (I was going to limp home but had to goto the dealer) Turned out to be a speed sensor on the back of the transmission. If I remember correctly, and I seldom do, the motor goes into a protect kinda mode when it can't sense all the things it wants too. |
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yoopr
Joined: 01 Dec 2004
Posts: 12866
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| Posted: Tue Jan 02, 2007 10:32 pm Post subject: |
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| try putting on a new Fuel filter |
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yurkym
Joined: 15 Apr 2006
Posts: 18
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| Posted: Tue Jan 02, 2007 11:14 pm Post subject: |
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| changed the fuel filter right off, but the sensor................ah |
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bob h
Joined: 15 Oct 2006
Posts: 664
Location: Nb
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| Posted: Wed Jan 03, 2007 5:31 pm Post subject: |
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yurkym wrote: changed the fuel filter right off, but the sensor................ah
what sensor ? |
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yurkym
Joined: 15 Apr 2006
Posts: 18
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| Posted: Wed Jan 03, 2007 11:23 pm Post subject: |
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I put her in the shop today to check all fuel lines and that sensor( the speed sensor on the trans)
Will let you know if thats the problem....thanks. |
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bob h
Joined: 15 Oct 2006
Posts: 664
Location: Nb
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| Posted: Thu Jan 04, 2007 7:57 am Post subject: |
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yurkym wrote: I put her in the shop today to check all fuel lines and that sensor( the speed sensor on the trans)
Will let you know if thats the problem....thanks.
before you change it ;
back off the jam nut,
turn it all the way "in", careful not to break
then back it off 1/2 turn, tighten jam nut.
this re-sets the sensor air gap. as long as you have a threaded sensor, you will have to set the new one as well. |
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marylandkw
Joined: 06 Sep 2005
Posts: 474
Location: Maryland
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| Posted: Fri Jan 05, 2007 8:29 pm Post subject: |
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yurkym wrote: I put her in the shop today to check all fuel lines and that sensor( the speed sensor on the trans)
Will let you know if thats the problem....thanks.
Any answer yet? |
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Splitshifter
Joined: 19 Jun 2006
Posts: 644
Location: Right here
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| Posted: Fri Jan 05, 2007 8:48 pm Post subject: |
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marylandkw wrote:
I had this problem a few years back, was interment at first and then became steady after about 300 miles (I was going to limp home but had to goto the dealer) Turned out to be a speed sensor on the back of the transmission. If I remember correctly, and I seldom do, the motor goes into a protect kinda mode when it can't sense all the things it wants too.
I will second that.
Had that happen a few years ago on a Mack.
Speed sensor on trans output shaft failed. Speedo registered zero MPH, engine was totally devoid of power.
I would assume that without a MPH signal, the ECM thinks the truck isn't going anywhere, and wont allow the engine to receive full fuel.
Replaced the speed sensor and all was well. |
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yurkym
Joined: 15 Apr 2006
Posts: 18
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| Posted: Sun Jan 07, 2007 1:21 am Post subject: |
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I appreciate the responses, but she is still at the shop . We are going to get her on Monday. The shop did replace the sensor and all the fuel lines were fine. So we'll let you know>
Thank you |
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bob h
Joined: 15 Oct 2006
Posts: 664
Location: Nb
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| Posted: Mon Jan 08, 2007 7:55 am Post subject: |
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yurkym wrote: I appreciate the responses, but she is still at the shop . We are going to get her on Monday. The shop did replace the sensor and all the fuel lines were fine. So we'll let you know>
Thank you
it doesn't make any sense whatsoever that the fuel lines could be causing this problem. |
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bob h
Joined: 15 Oct 2006
Posts: 664
Location: Nb
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| Posted: Mon Jan 08, 2007 8:35 am Post subject: |
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Splitshifter wrote: marylandkw wrote:
I had this problem a few years back, was interment at first and then became steady after about 300 miles (I was going to limp home but had to goto the dealer) Turned out to be a speed sensor on the back of the transmission. If I remember correctly, and I seldom do, the motor goes into a protect kinda mode when it can't sense all the things it wants too.
I will second that.
Had that happen a few years ago on a Mack.
Speed sensor on trans output shaft failed. Speedo registered zero MPH, engine was totally devoid of power.
I would assume that without a MPH signal, the ECM thinks the truck isn't going anywhere, and wont allow the engine to receive full fuel.
Replaced the speed sensor and all was well.
it's irrelevant to know this, but; the ecm is still aware that the truck is moving, even without the vss. it simply has lost a parameter that allows the engine to operate efficiently. this is a programmable parameter in most ecms, meaning that it can be disabled. |
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marylandkw
Joined: 06 Sep 2005
Posts: 474
Location: Maryland
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| Posted: Mon Jan 08, 2007 11:49 am Post subject: |
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Bob, just out of morbid curiosity, How does the ECM know I am moving without the VSS?
I sat here and thought about it and I can't figure it out. I am not saying you are wrong, I am saying I am slow :lol: |
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bob h
Joined: 15 Oct 2006
Posts: 664
Location: Nb
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| Posted: Mon Jan 08, 2007 5:43 pm Post subject: |
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marylandkw wrote: Bob, just out of morbid curiosity, How does the ECM know I am moving without the VSS?
I sat here and thought about it and I can't figure it out. I am not saying you are wrong, I am saying I am slow :lol:
hmmmmmm, there's a question i've never been asked :)
i'm only gonna attempt to turn the lights on ...
when you press the accelerator pedal down, the ecm sees this as "fuel demand"; if you push the pedal all the way to the floor, this is seen as 100% fuel demand.
if a truck is unloaded, 100% fuel demand will take the engine from 700 to 1600 rpms in X seconds. if the same vehicle is fully loaded, it will require Y seconds (longer than X) to get to 1600 rpm with 100% fuel demand... ...this is (sort of) how the ecm calculates engine load...,
and the vehicle must be moving to load the engine ....... ........ ....... ........ right?!?
now, if that same vehicle is sitting still in neutral, and you push the accelerator pedal all the way down (100% fuel demand), how long will it take for the engine rpm to reach 1600? ... much quicker than the loaded vehicle at 100% demand, correct?
this would only be one basic strategy, i'm sure there's more. |
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yurkym
Joined: 15 Apr 2006
Posts: 18
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| Posted: Sat Jan 13, 2007 3:59 pm Post subject: |
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Thank you Thank you Thank you....one and all. It was the speed sensor. And she is up and running.
Sorry I took so long to thank you all but we picked her up Monday morning and just got home with her today. We changed out the fuel lines because they were lookong old...we try to do as much preventitive maintance as possibble.
Again "love you guys" |
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