802a Idle fluctuations

[Bcoffey1123]

I have a second 802a that I just brought home. Put batteries in and it ran perfectly (362 hrs). While it was running, a friend was tightening the battery terminal and pulled the negative off, killing the engine. I hooked it back up and now it runs very rough and hz are bouncing all over the place. Any thoughts?

 

[Ray70]

Hello, well for starters, pulling off 1 battery cable should not have killed the engine. The alternator should have kept it going, so in addition to the rough running condition you also have a charging system problem.
As to the rough running, I assume the engine rpm is fluctuating in tune with the Hz meter fluctuating? ( indicating a mechanical engine problem rather than an electrical issue with the Hz meter)
My first thought is a lack of sufficient fuel pressure or air in the fuel system.
Being the machine is new to you have you gone through the filters etc.?
I think you need to check the fuel supply and filters to make sure everything is ok there. Keep in mind that a fuel pump that makes noise doesn't mean it is working correctly.
If the pumps and filters are all ok its possible that just running the fuel pump in the prime / run position may clear it up, if you have air in the fuel system.
Likewise, running the machine a little may also clear it up if the problem is just air.
While doing this, it's always a good idea to add a little SeaFoam or ATF to you fuel to act as a cleaner / lubricant.
Once the fuel system is checked out, if the symptoms still remain we can move on to the next steps.

As to the possible alternator issue, first thing to do is check the fuse in the gray fuse holder located to the left of you AC selector switch, inside the control cubicle.

 

[Bcoffey1123]

Hello, well for starters, pulling off 1 battery cable should not have killed the engine. The alternator should have kept it going, so in addition to the rough running condition you also have a charging system problem.
As to the rough running, I assume the engine rpm is fluctuating in tune with the Hz meter fluctuating? ( indicating a mechanical engine problem rather than an electrical issue with the Hz meter)
My first thought is a lack of sufficient fuel pressure or air in the fuel system.
Being the machine is new to you have you gone through the filters etc.?
I think you need to check the fuel supply and filters to make sure everything is ok there. Keep in mind that a fuel pump that makes noise doesn't mean it is working correctly.
If the pumps and filters are all ok its possible that just running the fuel pump in the prime / run position may clear it up, if you have air in the fuel system.
Likewise, running the machine a little may also clear it up if the problem is just air.
While doing this, it's always a good idea to add a little SeaFoam or ATF to you fuel to act as a cleaner / lubricant.
Once the fuel system is checked out, if the symptoms still remain we can move on to the next steps.

As to the possible alternator issue, first thing to do is check the fuse in the gray fuse holder located to the left of you AC selector switch, inside the control cubicle.

Thank you for your response. I have checked all filters and all looks good. I will try the seafoam as well. It runs as it should when cold, once it warms it begins to fluctuate, and yes it is the engine rpm and hz. I do believe I have an alternator issue it is showing a negative on the charge, I have not verified with a meter yet. I agree the alternator should have kept it running and the fuse looks good it was the first thing I’ve checked. I am wondering if the alternator issue would cause the engine to fluctuate once running for a few minutes, seeing that is only pulling from the batteries and they are losing charge.

 

[Ray70]

It sounds like you are just running the machine without a load? If you are set up to apply some load to it, I would get the batteries charged up fully and then run it under maybe a 25% load and see what happens. You may have a weak fuel pump that is not supplying enough fuel to keep you going strong. This would result in it acting up quicker if you run under a bit of a load.
Is your primary pump square or round? The square pumps are notorious for going bad, the round E1074 pump was the military's "Better" replacement, but still prone to failure.
A square pump is easily swapped out with an Airtex E8035 available for about $40.
If your Alternator fuse is good and you are showing a negative on the ammeter, you probably have a bad alternator. You should see about 28V when running if the alternator is working. No output from the alternator is often caused by a bad regulator ( mounted on the back of the alternator, but they are hard to come by, so you may need to get a replacement alternator. For now you can put a battery charger ( or 2 ) into the courtesy outlet to charge them while running and testing the engine problem.

 

[America]

How much do the hertz change?