Pre-fill new Fuel Filters???

[clt_capt]

I was doing my spring maintenance today - Changing oil, Filters, etc

I get to the inline CAT fuel filters - unwrap them - and the instructions say to not pre-fill with fuel... I have always understood that air is a bad thing in a diesel's fuel system...

What is the possible logic???

Have I always been doing the fuel filters the wrong way???

If so, what is the correct way?

[Avenger]

Everything in life is a compromise. By pre-filling you are putting unfiltered fuel in the system. So you are taking a chance with your fuel injection. In a perfect world you'll have either a manual or electric priming pump to fill the filter after it is installed, then you open a line or bleeding port and bleed the air out of the system. Done properly there will be no issues with air.

Now in the real world, most manufacturers are... what does the birdie say? "Cheep, cheep, cheep" and have eliminated hand primers. So if you haven't installed your own you're very short on options. Another scenario, you're pitching around in heavy seas and the crud in your tank gets picked up and plugs a filter. You need to get running again in a hurry. Of course it will be hard to pour fuel in the filter while you're gettting knocked around, but it's much faster to fill, spin and go.

So the technically correct solution is to have a priming pump. An electric one makes life easier, but expensive and complex. Personally I'd also have a manual pump as a backup anyway.

BTW if you have a common-rail fuel system the tolerances for dirt are much less than older systems. Unless you're truly desperate i.e. willing to pop several grand to get out of the spot you're in, never put unfiltered fuel in a common-rail engine.

[JD5652]

I always prefill....but I have 671's and no common rail technology to be concerned with.... Avenger makes a good point about the common rail engines......

[clt_capt]

I have 3126s - No Common rail - I always get fresh diesel and filter it before pouring it into the fuel filter... Unfortunately I don't have a manual priming pump...

Thanks.

[seapower]

Common Rail engines are not supposed to be pre-filled, because of the contaminated fuel concern. If your CAT filter say's not to pre-fill then do not. The air should be vented from the fuel system by way of the fuel return system. There are a ffew fuel systems out there that "vent" this way. That being said, I ALWAY's pre-fill fuel (I know my fuel source and it is filtered) AND lube oil filter's when serviceing. Of course you can't pre-fill an inverted oil filter. It alway's amaze's me at the number of owner's (and so called mechanic's) that don't pre-fill lube oil filter's. By not pre-filling the lube oil filter, at crank-up your engine is running dry before the filter is filled by the oil pump. I know it may not take long to fill, but the cam shaft in most engines is the last in line for lubrication, then the oil is dumped back into the sump. I wouldn't want to run a "dry" cam in my engine. Frank

[clt_capt]

Thanks Guys.

Frank - I always pre-fill lube filters - thankfully they are not inverted.