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tommildren · 06-22-2010, 12:34 PM

I was talking to the head mechanic at an old established shop that owns many of its own trucks and tractors and they service rv's alot and I told him the mechanic at an allison shop said he was worried about filling the second fuel filter with diesel fuel before installing it as it's attached to the engine next to the starter because of a spill/ fire possibility so he installed it dry hoping he wouldn't have a problem starting the engine. ( which turned out ok ) PS. I thought I had a trans shifting problem, thats why I was at the allison shop. ended up being pluged filters from algea contamination.

this other mechanic said in all his years servicing his companies trucks and customers rv's he has never filled the fuel filters with diesel fuel rather he fills them with ATF fluid. He said that ATF has the same ingrediants as those expensive diesel fuel additives for cleaning valves/ engines we buy in the stores and its cheaper and there is no fire danger

anybody ever hear of this?

Chuck 1935 · 06-22-2010, 12:43 PM

I always use ATF when changing fuel filters. The reasoning is that you don't want ANY dirt to contaminate the fuel. If you had any Diesel fuel sitting around you have no idea of how clean that fuel is. You know a nice fresh bottle of ATF is 100% clean.

Route 66 · 06-22-2010, 01:26 PM

Cummins does not recommend that, nor filling the fuel filters with anything on my ISL.

The risk of contamination is too great, however many shops will fill the filters to avoid the priming process which saves time.

Chuck 1935 · 06-22-2010, 01:55 PM

I agree with you Dirk, Contamination is the problem, that is why, if you prime, you use an unopened, fresh bottle of ATF. I am sure the reason that Cummins says don't prime is because of all the knuckle draggers out there that try and pass themselves off as real mechanics. That is not an aspersion of mechanics but of all the wanna be's.
If you are doing the job yourself and are confident in your ability, pre filling the filter can save you from having a problem.

MBnKen · 06-22-2010, 07:54 PM

Not all Cummins engines are the same so blanket statements like don't fill the fuel filter are not correct. The ISM has no lift pump and uses a single filter on the Spartan chassis. You must prefill the filter according to Cummins and Spartan. You can insert a brass threaded nipple in the center of the fuel filter and then slowly pour clean diesel fuel into the outer filter holes. The fuel is filtered just like when working on the mount. I can't speak to the ATF fluid, pro or con, I just prefer not to use it and have had no problems pre-filling the fuel filter as noted.
By the way, there is bold print on the side of the ISM filter telling you to prefill it before installing.

wa8yxm · 06-22-2010, 08:02 PM

The fire danger from a Diesel fuel spill is very small by the way..

I have seen a flash pan (This is a pan that is very shallow) filled with Diesel and a lit match thrown into the pan,,, What do you think happend.

Now, if you filled the pan with water instead of Diesel.... same thing would have happened.

Fill the pan with gasoline and..... You'd better jump back as you throw the match cause it's going to go WHOOOOOMPH!!

LindyT · 06-23-2010, 03:28 PM

I've always pre-filled filters. I did so with my ISC and I have to with my ISM.

ATF is old-school... the old timers have done that since the dawn of time. I don't like the idea personally, though I have no specific reason why... it just seems like a bad idea in a modern diesel.

Personally, I pre-fill with Sea Foam. Presumably uncontaminated (and don't assume because it comes in a sealed bottle that it's 100% contaminant free...) and gives a great shock treatment to the injectors. Great stuff.

Chuck 1935 · 06-23-2010, 04:04 PM

Lindy T............Old School are you kidding ? I thought I was on the cutting edge. Heck, I'm still driving my 33 Ford from High School thats how up to date I am. Next time I go to the beach I'll scoop up some of that there Sea Foam . I like to save money so thats a whole lot cheaper than that darned old ATF. Thanks for the tip.