I had a brief moment to start some very idle equipment the other day. I had 3 of my Caterpillar D2 and D4s not wishing to start; I discovered the fuel racks having a stuck plunger in each one. After getting out my tools and some loose juice, I got them all running. All of these machines are indoors and have not been ran in months.
My Kenworth truck with the small cam "400" won't start either!
Some of us think it has something to do with the new diesel blends being sold here in California?
I normally add some type of conditioner in my fuel such as some ATF fluid, Seafoam additive or Stanadyne fuel treatment for additional protection. 
Did I just get unlucky from lack of use, or is it because of the fuel? Not the end of the world, but an annoyance to say the least.
Any recommendations besides starting them each week or selling them off?
TIA as always, JM.

I don't have any recommendations for you other than to sell them all to me 😆

CrawlerAddict 

lol buy 100% diesel fuel with no blend, or if you buy blend I cut mine with kerosene.

we use flash lube diesel conditioner in our diesels. solves the lubricity problem for older engines. and yes juiceman you need to play with your toys more often.

Mr Juiceman I will try to not write a novel here but yes, in my opinion we all need to use a quality additive package for our fuel nowadays. Mandatory, no questions asked for me. You can almost eliminate DPF issues with a quality additive and now that we all have no choice but to buy the renewable diesel on the west states, I always pick one with a water dispersant which I dump in the bulk tank at the delivery. Will eliminate the condensation water, which eliminates the growth medium where algae forms.
The newer common rail diesels really benefit from the added lubricity as well. Superior wear scar prevention to old traditional 2-stroke oil, ATF, etc.
My current favorites are the Archoil products, and Schaeffer's Carbon Treat. I also occasionally run some Pittsburgh Power fuel catalyst in our DPF stuff, but I think it's not likely necessary when using the Archoil products.
Anyways, even this old stuff I treat the tanks so everything gets the additive. Due to tax breaks, we as consumers get no choice. Basically all 3 West Coast states we all get renewable diesel which isn't bad by itself, but has some extra tendencies to attract moisture, and it's extra cleaning power will break loose films in existing tanks, and potentially cause filters to dirty for awhile when changing over. Usually that problem clears up once the fuel storage tanks aren't "dirty" any longer. But that is what gave biodiesel a bad name at first around some operations at least.

Hi, juiceman.
If you cain't taykem out-n-exercise 'em more reg'lar like, maybe you should GIVE them to CrawlerAddict so that they can have a CARING home. LOL.

Just my 0.02.

Thanks for the responses everyone. I generally only take delivery of 2000 gallons at a time here, and that varies during the season. I will have to be more diligent about adding something to my bulk tanks. Generally, each machine still gets a special dose of Seafoam additive, Marvel's, or something added to the tank, plus the pony fuel if so equipped.
I ponder using the contents of a barrel of kerosene that we have tucked away in the corner for 40 some years.
Has anyone used any "Jet A"? Is it not just highly refined diesel fuel? Same about aviation fuel for starting motors, does it really make a difference?
I agree wholeheartedly about getting them all out of mothballs and giving them all a good run.
As soon as the "Play Pen" is ready, it will give me a chance to let them work some. One of my outside wrench people made the comment that my building(s) should be a tad full by now. (If he only knew).
Deas got me thinking, I just did a count of D4's here, and it wasn't pretty. I need help... Thank goodness that CrawlerAddict relieved me of a few over the course of a year. I am "down" to 15 here. My sexist thought was it is just like a woman's wardrobe... Geez, I don't know what to wear...In this case, what to drive!
I am really having a strange thought about my dad; prior to his passing he told my mother to gather up his "fleet" of D4's (which he had none) as they were scattered about throughout the state. Maybe he channeled that through me??? Creepy!
Sorry for the ramblings, but that is what happens when I have a good cup of coffee and having a great day! JM

For my ponies I use the 100 Low Lead I can get over at the small airport by my farm. Just drive over and pump a couple 5gal cans at the self serve. The care taker doesn't care since he knows I'm not running it in my pickup truck. That stuff lasts a long time if it doesn't evaporate. But if it does; there's nothing left in the tank and it dries up clean.
In a pinch; I've put the Tru-Fuel 50:1 chainsaw fuel in my pony tank when I can't find any other gas. That stuff at least puts a oil film in the tank keeping the rust down.

the reason to use avgas in these old petrol engines is aviation fuel still has lead in it.
but you can use flash lube valve saver instead. very economical as 1 gallon treats 1000 gallons as its a 1 percent mix ratio. their diesel additive is the same ratio.

the problem with using avgas is you need a friendly pilot or lame to obtain it and dont get caught as its for aviation use only. fines do apply if caught.

and dont use kerosene that will make it worse as its a cutting agent not a lubricant. kero is used in machine shop for surface grinding and honing operations we have to add oil to it so its not so dry.

the one place biofuel isn't allowed is maritime operations due to its higher wax content. you don't want wax plugging issues on a ship. as most large vessels use centrifuges to clean the fuel the wax get separated in the centrifuge and is a pain in the arse to deal with. according to a marine engineer I've known for years. apparently because the fuel tanks are below the water line for stability the cold from the ocean makes the wax form.

biodiesel  is fine in land based equipment provided it was made correctly. as it is made by blending vegetable oils with caustic soda and methanol if the ratio is not calculated correctly and/or the ingredients not measured correctly you can get a incomplete reaction and excess methanol or caustic can be left behind in the resulting fuel which causes corrosion and dissolves seals and hoses. so only by from reputable sources. the first half is the same as soap making then its a transesterification process to get the fuel once the gylcerine is separated off.

it's a interesting process if you a science and engineering buff like me.