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Primary fuel filter location 2004 HR Neptune 36PDQ 300 ISB


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Stuck on the side of the road.  Have fuel filters but can't seem to locate the primary fuel filter. Does anyone know where it is?

Edited by RBRODDER
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  • RBRODDER changed the title to Primary fuel filter location 2004 HR Neptune 36PDQ 300 ISB

Not sure if we have the same coach setup- but the fuel/water separator should be on the passenger side of the motor toward the front. The main fuel filter for me was in the radiator bay. 
 

Best of luck!

 

Nick 

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On my HR the "primary/main" fuel filter is mounted in a compartment on the drivers side, behind the A/C condenser.  My condenser swings out to open after unlatching it with a special key.  My primary filter had a clear bottom....  the secondary filter on my 8.3 Cummins, is mounted to the passenger's side of the engine (as engine is mounted in coach).  That filter has a electric sensor plugged into it (that detects water).  I am not familiar with a Neptune....  hope you get it going

Ken

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Neptune is on an R4RR chassis with a ISB engine.  Could be quite different than the R8RR / ISC Endeavor.  Just sayin

RBRODDER, when you do find the primary filter don't forget to pre-fill the new filter and go through the key-on for 30 sec, key-off then 30 sec key-on again for 5x before starting the engine.  This gives the lift pump a chance to suck fuel from the tank, finish filling the fuel filter and pressurizing the engine fuel pump.  Good luck. 

What symptoms led to parking the coach on the side of the road?  This might not be a clogged fuel filter . . . .

- bob

Edited by cbr046
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2 hours ago, cbr046 said:

Neptune is on an R4RR chassis with a ISB engine.  Could be quite different than the R8RR / ISC Endeavor.  Just sayin

RBRODDER, when you do find the primary filter don't forget to pre-fill the new filter and go through the key-on for 30 sec, key-off then 30 sec key-on again for 5x before starting the engine.  This gives the lift pump a chance to suck fuel from the tank, finish filling the fuel filter and pressurizing the engine fuel pump.  Good luck. 

What symptoms led to parking the coach on the side of the road?  This might not be a clogged fuel filter . . . .

- bob

Bob, 

A little back history, we purchased  the M/H about  a year ago and had fuel gauge issues and I changed the sending unit which seemed to solve the fuel gauge issues.  While doing that I looked in the tank and didn't see anything obnoxious, however I had added some Diesel 911 to be on the safe side as I didn't know the condition of the system (microbial contamination) we had just filled up and was about 5 miles or so cruising down the road about 55 mph and started losing power, I pulled off the side of the road and the engine died.  I thought that I may have purchased bad fuel even though I have purchased fuel at the same station through the years as the station is close to my home and I also have a diesel pickup.  I had intended to change the filters and had them with me. The first thing I did was drain some fuel from the secondary filter to see if I had possible water in the fuel. I didn't see anything obvious but, I had nothing to catch the fuel in to examine it and didn't want to create a fuel spill on the side of the road. Cleared the codes and fired it up and seemed fine. Albeit the oul pressure seemed low at idle but would be around 60 psi off idle. We drove around 10 mor miles and it started losing power again.  Made it to a truck stop and parked it. Ended up having a friend come out as I didn't have a filter wrench and couldn't get the secondary filter off. I searched everywhere for the primary filter to no avail.  Got the secondary filter off and it was literally clogged with what appears to be microbial growth. Clean up the filter base and blew everything off with air. Installed the new secondary filter and got it primed and fired it up. Made it down the road about 25 miles and it started to surge...pulled off the road again and pulled the secondary filter which had some junk in it but not as bad as previously.  Same thing, cleaned up the filter and managed to finally make it to our destination...I crawled and searched everywhere and still have not found a primary filter. Which if there was a primary filter....how is all the crud making to the secondary filter...  and yes, I flipped when I saw the condition of the secondary filter... 

Resized_20220826_200055.jpeg

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Rich,

The filter in the photo that you posted is (by part number) the primary filter.  It has a drain valve on the bottom..??  Is it mounted on the engine??

My secondary filter on my 8.3 Cummins is mounted on the engine between the lift pump and the injector pump, it has electrical wires and connector plugged into it, not a drain valve. That wire/plug senses water and lights a light on the dash.  In theory, the primary filter should not allow water to pass to that filter... so that light should never come on. 

I believe you have found your primary filter... and it's ugly!

Ken

Edited by Cubflyer
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That's bizarre . . . . if I recall correctly those holes are on the output side of the filter.  This would be an upside down image:

fuel-filter-fuel-flow-diagram-001-jpg.298745

I couldn't find any info on the CarQuest 96277 filter (like micron filtering size).  https://shop.advanceautoparts.com/p/carquest-premium-fuel-water-separator-spin-on-with-drain-96277/11312261-P  I'd replace with Fleetguard (OEM), Donaldson or Wix if you can, but we need to get you down the road again . . . . . 

The primary filter will be mounted on the chassis . . . . somewhere.  Our ISC's are on the drivers side toward the rear.  A new filter should be pre-filled (at least 3/4). 

The secondary filter will be somewhere between the lift pump and CAPS fuel pump.  All 3 will be attached to the engine.  On the ISC it's on the passenger side.  I think the ISB is similar.  The secondary filter will have a clear bowl at the bottom with drain.  That's for the OEM filter.  It should be filled by the lift pump (on-off-on proceedure).

I'm wondering if something isn't chemically reacting to the fuel from the last fillup . . . .

Don't be afraid to use one of momma's glasses to capture and look at the fuel.  Keep changing filters. 

This is probably the biggest reason many of us have installed the FASS fuel pump / filter system.  That and to keep our expensive CAPS pumps pressurized and not sucking fuel from the tank.

Good luck,

- bob

 

 

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13 minutes ago, 96 EVO said:

Nope!

Those are inlet holes.

I hope so!  Makes sense that a filter would have pressure on the media from the outside -> inside to keep the filter from exploding.  Harder to implode.

- bob

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