Ok, yes, I read through my Newmar, Cummins and every other piece of paper in the 1567 pages of FSM handouts in my coach as well as searched exhaustively for answers on this forum that I routinely lurk on (enjoyably) and I'm coming up with about a 95% confidence level that on my 2008 Newmar KSDP 400 ISL I should simply spin off the old fuel filters, spin on new ones (dry), cycle (without starting) my ignition 4-5X to purge air in the lines, then start normally...Constructive comments will be appreciated...TIATodd

That's what I do on my '03 400ISL, works for me.

I had a 400 ISL in a Monaco and changed the filters once a year for ten years and never liked putting them on dry, at least not the primary. The two times I tried, it didn't start. To me, it's not worth the aggravation. I like to put the primary filter on after filling it. Use your thumb or a plug to block the center hole and fill around the outer edges. Install the filter and start the coach. Once you know it's running properly, shut it off and install the secondary filter. My new coach has a hand primer, so it's a little different.

You should have a shut off valve so you can shut off fuel to the filters. Turn it off and remove the filters one at a time and replace. Turn on the fuel valve and use the ignition to prime the filters. Do this 6-10 times, do not engage the starter. If it doesn't start, then repeat the 6-10 times prime.Works for me with a ISC

I always fill my filters before installing, it's in my manual. Cummins ISM.....Dennis

it is ok to prefill the primary filter (the first one from the tank)install the secondary filter dry. the common rail fuel systems have a lot closer clearances in the high pres pump and the injectors and that little bit of dirt that may get into the filter when filling it can cause fuel system issues. also if there are clearance issues getting the filter in position to install it is a good idea to cover the filter with a clean cloth until it is in position to install then remove the cloth being carful not to let any dirt that may have fell on it drop into the filter.

Primary & Secondary Fuel filter change question

gmctoyman
Explorer
May 24, 2016
That's what I do on my '03 400ISL, works for me.
DSDP_Don
Explorer
May 24, 2016
I had a 400 ISL in a Monaco and changed the filters once a year for ten years and never liked putting them on dry, at least not the primary. The two times I tried, it didn't start. To me, it's not worth the aggravation. I like to put the primary filter on after filling it. Use your thumb or a plug to block the center hole and fill around the outer edges. Install the filter and start the coach. Once you know it's running properly, shut it off and install the secondary filter.

My new coach has a hand primer, so it's a little different.
dons2346
Explorer
May 24, 2016
You should have a shut off valve so you can shut off fuel to the filters. Turn it off and remove the filters one at a time and replace. Turn on the fuel valve and use the ignition to prime the filters. Do this 6-10 times, do not engage the starter. If it doesn't start, then repeat the 6-10 times prime.

Works for me with a ISC
Executive45
Explorer III
May 24, 2016
I always fill my filters before installing, it's in my manual. Cummins ISM.....Dennis
11178adm
Explorer
May 24, 2016
it is ok to prefill the primary filter (the first one from the tank)
install the secondary filter dry. the common rail fuel systems have a lot closer clearances in the high pres pump and the injectors and that little bit of dirt that may get into the filter when filling it can cause fuel system issues. also if there are clearance issues getting the filter in position to install it is a good idea to cover the filter with a clean cloth until it is in position to install then remove the cloth being carful not to let any dirt that may have fell on it drop into the filter.
smlranger
Explorer
May 24, 2016
I always pre-fill mine. The one time I did not, I had issues getting it started in spite of following the instructions.

I use Fleetguard filters and they come with the plastic plug for the center hole so easy to pre-fill.

As Don noted, not worth the aggravation of having issues getting the coach started if you install them dry.
Blaster_Man
Explorer
May 24, 2016
Executive wrote:
...I always fill my filters before installing,...

That's what I did on my ISL 400. I used a boat fuel filter to filter the fuel prior to putting it in the two spin on filters.
YC_1
Nomad
May 24, 2016
Yes my manual says to install dry. Never again. I believe it may be due to gravity draining the fuel lines back into the tank but cycling the ignition switch 30 times will not do it for me.

As Don says. Prefill and you will get it started.
SpurHntr
Explorer
May 24, 2016
Much thanks to ALL who replied.
Good info.
Leaning towards the prefilling using an inline filter to do so.
That seems like a win win seeing many seem to have had issues installing em bone dry?
Ivylog
Explorer III
May 25, 2016
My ISL is the only diesel I put the filter on DRY. Turn the key on for 30 seconds (length of time my electric lift pump runs). Do this 4-5 times... 2+ minutes run time. Starts every time as I change my primary filter when I cannot maintain 65 mph up a long hill... usually 25K+ miles.