Community Forums

danes-on-tour · 02-06-2008, 06:31 AM

Hi again

I am itching to have a go at changing the primary and secondary fuel filter my self. This is on a 400HP Cummins in my 2007 Diplomat.

On one hand it would be nice to able to do this if I should ever need this in an emergency.

On the other hand I have no experience with this type of work or with diesel engines. To the best of my knowledge I could have some problems with trapped air and I obviously don't want to cause my self a problem that I can't solve.

I am a technically minded person but would I (again) be better of leaving this to the professionals? I have been looking for a step-by-step manual on the Internet but I haven't found one yet.

Thanks

danes-on-tour · 02-06-2008, 06:31 AM

Hi again

I am itching to have a go at changing the primary and secondary fuel filter my self. This is on a 400HP Cummins in my 2007 Diplomat.

On one hand it would be nice to able to do this if I should ever need this in an emergency.

On the other hand I have no experience with this type of work or with diesel engines. To the best of my knowledge I could have some problems with trapped air and I obviously don't want to cause my self a problem that I can't solve.

I am a technically minded person but would I (again) be better of leaving this to the professionals? I have been looking for a step-by-step manual on the Internet but I haven't found one yet.

Thanks

gizmo · 02-06-2008, 06:45 AM

Changing filters is not hard to do. Most important, is to change one filter at a time.after replacing filter.turn on ingnition . let filter fill.(do not start) do this a couple of times.then start engine. let run a few minutes . repeat procedure for second filter .

SilverBlivit · 02-06-2008, 06:58 AM

I am not familiar with 400 but have a 350 Cummins which is similar. If the fuel filters are vertical, screw-on type, then it is a very simple task.

Remove old filter.

Fill new filter completely with diesel fuel.

With a steady hand, screw new filter in place without loosing any of fuel. Wipe clean any excess fuel.

Re-start engine and idle for 2 minutes.
Should be ready for road.

Don't forget to drain or replace the water separator.

Same as above with gen set. Also,Gen set can be purged of air with starter if required. I use starter duty cycle; 10 seconds on ,30 seconds off; 10 seconds on, 5 minutes off.

I have done the above successfully. However, there are probably Cummins experts on the forum who can give you, a more correct, "by the book" method.

Route 66 · 02-06-2008, 07:44 AM

Cummins specifically DOES NOT recommend filling the ISL filters before installing them.

You would be putting unfiltered fuel in the system.

Gizmo has it right.

SilverBlivit · 02-06-2008, 08:10 AM

Good Point, Dirk.

Too many years with Dozers and Big Iron, and too many years away from the precision of airplanes.

Route 66 · 02-06-2008, 09:26 AM

Of course, this is not to say that some/many/most shops prefill the filter because it's faster.

Latitude · 02-06-2008, 03:47 PM

I have always filled mine with fuel prior to installing. Put a bit of grease on rubber gasket put on hand tight and snug up with filter wrench.

Dirk The dirt/water etc stays in filter so I 'Think' the bit you put in filter would go thru filter.

Rick

SilverBlivit · 02-06-2008, 04:15 PM

Thanks Dirk, Latitude, for the rescue, you are both right on all points.

Route 66 · 02-06-2008, 04:24 PM

One would normally fill the filter by pouring fuel in the large center hole, however, that is the outlet of the filter.

There is just too much of a chance for contaminated fuel to be introduced into the system. We're talking micron sized particles.

With the stakes so high (price of an injector pump), installing filters dry is preferable.

Gary RVRoamer · 02-06-2008, 04:43 PM

Dirk is right - I got the same advice direct from a Cummins rep at a rally last fall. DO NOT pour unfiltered fuel into the big hole in the filter body - that is the outlet side. Of course, if it is the primary filter that fuel is going through the secondary anyway, so any goof will get caught. But if its is the secondary it is going straight to the injection pump without further filtering. On that one, pour the fuel into the small holes around the rim so that it goes through the filter media.

Better yet, leave it dry and cycle the key on/off several times and let the electric fuel pump push the fuel through the filter for you. Then up can start it.

On older mechanical pump engines, you have to prefill or use a manual priming pump (some filters or fuel systems have a priming pump built in - your mileage may vary)

Camelot Camper · 02-06-2008, 05:13 PM

I new to desiel engines also, so I'm curious how the trapped air in the filter leaves the fuel system without creating an airlock?

CC

gizmo · 02-06-2008, 06:08 PM

i always wondered where the air go's.
a good source for air/oil/fuel filters is filterbarn.com

SilverBlivit · 02-06-2008, 08:25 PM

Oh boy!!! I am the newbie here, and was trying to eat crow and let this die gracefully, but you guys....you gotta ask all the correct relevant questions.......so here goes.

Fill the freakn filter with good clean, thrice filtered diesel fuel, screw it in place, start the engine, let it idle a couple of minutes, and move on to a glass of wine.

Why add the worry of whether the pump completely fills the filter, and if, and when, it does, where did the air go, when you already know you have filled it with good, clean, thrice-filtered, liquid, diesel fuel and there is no air to be a problem.

This is done hundreds of times every day by competent mechanics all over the world. It is common practice in the earthmoving business. The filters are carried on the service truck, it is done in the field weekly on heavily used machines.