GW mentioned cleaning the OS, did you try that? Your responded to everything else clearly as done except that is why I ask. With it having sat three years the fuel that would have broke down in there will dirty it up bad, especially if it was off road dyed, or bio mix.
The good side of this is if you do go new ip with everything else sounding positive should be a lot of miles in the future.
Well, it's not quite as simple as pull the sensor out, clean it and pop it back in.
The OS is not supposed to be a "field serviceable" part as a DS4 is supposed to be set on a test stand, but it can be done if you're careful enough.
One way is to remove the top of the IP, scribe a line on the advance ring and then remove the sensor. Reinstall against the scribe and hope it's the same as it was.
The other is to frig with it until the calculated idle fuel rates are within spec.
Even with the scribe line, you should verify with the idle fuel rates once reinstalled. It's literally fractions of fractions of an inch in the difference between in and out of spec.
This is how gents used to do the "optic bump" (move the sensor on the advance ring) and if done wrong all sorts of odd throttle and fuel behavior can result. Primarily; overly touchy throttle.
You have to clean in behind the LED "eye". Which means you need to get a jet of cleaner up in there and flush the coke out. The stuff that gets in there is just in the diesel fuel itself and it accumulates over time. Sitting is no guarantee that it is a "dirty sensor" as I've pulled one out of a pump that had been sitting with fuel in it for more years than I know and it worked just fine without cleaning.
As much as I don't want to say it, the OP is getting more and more corralled into the bad OS paddock.
If I didn't know my own pump had the ceramic upgraded bits, I would have put the 300 or so bucks the OS is going to cost towards buying a new pump. Mine was worth saving though.
To the OP: if you were to ask my advice on which pump to buy, I'd go with a new unit from Stanadyne. it's going to cost somewhere around 1500 bucks, but it will last another ten years or so. Stanadyne will have a list of authorized dealers near you. Failing that, they will have a list of authorized rebuilders in your area and it should cost somewhere around a grand. At least you can be reasonably sure you will get the updated components from an authorized rebuilder. Not guaranteed, but better chance than anywhere else.
Of course, if you don't plan on keeping the truck that long, you can buy and OS from someone like Kennedy diesel and swap 'em out if you feel you are "savvy" enough to get 'er done yerself....
