Change in engine tone

[dan brooks]

I've noticed something strange over the past couple days. After starting the truck the first time each day or after getting off work, for the first several minutes the engine tone will change - it almost sounds like the KSB is kicking on and off (rattle gets much louder, then quiets down). Once the engine is up to operating temperature it seems to be normal. Haven't noticed any difference in performance of fuel mileage.



Any ideas?

 

[LEggers]

I've noticed something strange over the past couple days. After starting the truck the first time each day or after getting off work, for the first several minutes the engine tone will change - it almost sounds like the KSB is kicking on and off (rattle gets much louder, then quiets down). Once the engine is up to operating temperature it seems to be normal. Haven't noticed any difference in performance of fuel mileage.



Any ideas?

Could it be your grid heater coming on and off. THis puts a load on and off on the altornator.

Maybe you have a bearing or bushing in your altornator going out? I know its a long shot could also be a idler pulley bearing.

 

[dan brooks]

It hasn't been cold enough for the grid heaters, and there is no indication they are cycling (voltage meter is rock solid, no familiar "click" of the relays). The noise is almost certainly a result of something to do with the injection pump - either timing or fueling - and doesn't cycle consistently like it would if it were the grid heaters.

 

[BushWakr - RIP]

That sound is pretty common for a KSB function... . it will sound more metalic (sometimes subtle and other times fairly noticable) then after a few seconds/minute it will "soften" in tone and be "normal". As the intake air begins to warm the sensor will demand less KSB cycle time and eventually stop altogether.

One way to test this is to get the engine up to running temp and use a jumper wire from the "+" side of the battery to the KSB terminal. If you detect a similar/indentical result, you've found the answer.

As an aside, in my case for example, I will apply the 12v to the solenoid contact/remove, apply/remove until I begin to hear the sometimes subtle difference.



pb... .

 

[dan brooks]

Is the KSB supposed to cycle? I thought it was on steady until the temp sensor hit 90*, then off for good.



It didn't do it this morning, so I'll see what it does over the next few days. I'm just worried about an internal problem with the injection pump - I'm leaving for Oregon mid-April and don't need to have any problems on the road... .

 

[CGauthier]

I'm not sure but I think our Cummins may be kinda the same in that regard as the 7. 3 Furd as far as when cold the injection pump advances the timing a bit-that's what a shop that I would trust to do my diesel work told me...



CarlG

 

[dan brooks]

Well, hopefully everything is fine with it and I'm just worrying for no reason. It's just strange that it just started doing this - this isn't a subtle change in tone, but is very noticable.

 

[carlwest]

I know what sound you are talking about. My KSB is not working and it still made the noise. It also now flucuates radically in RPM, like the govenor spring is broken. I don't have the answer to the metalic sound fluctuation, but mine did the same thing. Sounds like your engine is runnning behind a smoke screen. Anybody have the part# for the KSB? Dodge told me if I wanted one I would have to find the part #. Tell me what do we PAY Them FOR???