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Topic: Any discussion of a cause of a1993 U300 rough idle?  (Read 1154 times) previous topic - next topic

Re: Any discussion of a cause of a1993 U300 rough idle?

Reply #20 –
Hi Cedric,

Pierce and others were a big help in getting my hydraulic pump belt alignment in good shape ( Hydraulic Pump Belt Alignment - 6V92TA ).

I'm curious about the fan "cutting in and out". My basic understanding from working on the system is that there is is not an on/off condition, only a slow/fast condition that is controlled by a hydraulic solenoid. The PO of my coach removed the electric head on my solenoid so it would default to high speed setting at all times.

If your fan is cycling back and forth between high and low speeds, it could be a solenoid issue too. Perhaps a simple test would be to remove the wiring block head from the solenoid?

Either way, it sounds as if a belt alignment and new tensioner are in order.

Chip

Re: Any discussion of a cause of a1993 U300 rough idle?

Reply #21 –
Quote from: Chip7 –
Hi Cedric,

Pierce and others were a big help in getting my hydraulic pump belt alignment in good shape ( Hydraulic Pump Belt Alignment - 6V92TA ).

I'm curious about the fan "cutting in and out". My basic understanding from working on the system is that there is is not an on/off condition, only a slow/fast condition that is controlled by a hydraulic solenoid. The PO of my coach removed the electric head on my solenoid so it would default to high speed setting at all times.
If your fan is cycling back and forth between high and low speeds, it could be a solenoid issue too. Perhaps a simple test would be to remove the wiring block head from the solenoid?
Either way, it sounds as if a belt alignment and new tensioner are in order.
Chip
With the fan in the high speed position, a huge amount of energy is wasted and your fuel mileage has to suffer. The U300 is already slow off a stop sign because of the "no smoke" setting on the ECU and the power robbing high setting on the fan will make it worse, especially up at altitude.  Perhaps a new "solenoid" is needed. You can always wire in a dash light with one of the extra wires that go from the engine compartment to the front so you can tell when it changes to high speed.

Pierce

Re: Any discussion of a cause of a1993 U300 rough idle?

Reply #22 –
This sounds similar to a condition I experienced with my 6V92, I call it a galloup when the hydraulic pump causes a pulsing of the tensioner actually causing it to jump and snap the belt. I had a post on here a while back about this condition. you can hear and see the strain being placed on the engine and pump. ::)

Re: Any discussion of a cause of a1993 U300 rough idle?

Reply #23 –
Gerry,

I looked but could not find your old post. Sounds as if that may be the problem. What did you do to cure the pulsing? Pulsing is going to eventually cause failure of the other components.

Pierce
 

Re: Any discussion of a cause of a1993 U300 rough idle?

Reply #24 –
I don't think the fan is changing speeds It acts more like every time the pump snaps in the fans spin a little. I think pulsing is a better description of the activity. Mileage was 7.5 from Maine to Virginia down 84 and 81.  Pulleys are lined up and tensioner spins freely.
Cedric