WX64 running VED 7, fuel issue leading to missfire/stall

Hi guys,


We've got a real problem on our hands, had a new driver in an older truck the other day for the first time on his own. He went and bought fuel from the one place in the Cleveland Metro area we told him not too (their storage tanks are disgusting, every time we've gone there, they've had water/rust in the fuel) and he got a nice amount of rust in his fuel, which somehow, bypassed the fuel filter. Absolutely zero clue as to how this happened, it's since been replaced and the new one is catching all the flakes.

So here's the deal, with the filter replaced and the lines flushed we're getting a misfire (ECM reads as cylinder 2 premature) which leads me to believe something is stuck open, somewhere, by this lovely little rust situation we have on our hands. The boss disagrees. I'm willing to believe just about anything he says- he was a diesel mechanic for 20 years prior to starting this buisness and a driver for about that long, but this is one of two Volvo's in our entire fleet and he has limited experience on them.


Anyone have any ideas about this that might be able to save a bit of money before we ship this out to a dealer?
Thanks!