Cm2250 Won't prime/no fuel in water separator
06-09-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #1
Cm2250 Won't prime/no fuel in water separator
Ok, I've searched high and low and I can't find anyone who has posted about my exact issue.
First,
2012 Cm2250
Freightliner Cascadia
Davco 382 water separator
New check valve in separator
New cap and seals separator
New primer/lift pump
New filters twice

My truck will not draw fuel into the water/separator. It occasionally will and did with the new water separator filter today. If I fill the bowl and run the truck, I can feel when It gets back down to the edge of the housing. It draws just enough fuel to pull but not great. Boost drops under load from 35 to 30 then after a while will go from 30-25.

The check valve had some trash in it and I changed it. I also replaced the fuel primer pump. I have checked fuel pressure with the primer pump and it's around 30psi. I let the pump run and pushed in the compucheck fitting and a ton of air came out of the high pressure filter. When I let the primer pump run and then shut off, I can hear air ( possible being drawn in) around the high pressure filter-ish area. There are no leaks under pressure though.

The truck has always had a weird howl noise on the driver side and the best I can figure is, it's something to do with the fuel filter. It only does warm and from 1400 rpm and up. I also have been fighting filters getting black in 5k miles or so. I've been using fppf killem and not really any results. I would imagine the fuel is just getting really hot.

Now, what I have done is verify that the lines to and from the tank are clear. They flow just fine. I have not checked the check valve In the intake side of the primer pump, nor the screen on the gear pump.

I don't have any codes. The truck just runs a little weak. It has a newer gear pump and injection pump. It also has that locomotive sound like one cylinder is either hitting harder or weaker. It's uncomfortable to me and I know it needs fixed. Please help!
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06-09-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #2
RE: Cm2250 Won't prime/no fuel in water separator
Maybe pressurize the fuel tanks to 10 psi (via the bleeder tubes) and let it sit for an hour... see if there are any fuel line leaks. CAUTION: whatever you do ... If you have pressurized the fuel tanks up to check for leaks ... NEVER try to open the fuel caps if the tanks are pressurized. It is usually enough force to break bones in your hand or severely injure someone as the cap jumps off.


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06-09-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #3
RE: Cm2250 Won't prime/no fuel in water separator
which filter are you using in the davco? I've had similar issues with my davco unit, old and a new one, where the fuel level would drop below the clear housing. Never did find an actual, definitive cause, but so far since I switched to the smaller filter I haven't had any issues. I have to look up which number it is, there's actually 4 that are compatible with that housing, 2 larger and 2 smaller.

Also, you need to double check that the o-rings are installed correctly. Check ALL the fuel lines going into/out of the main fuel filter.

Maybe try Biobor JF for a fuel treatment. There are a few causes, including 2 different groups of biologicals that respond differently to different products. I use the Biobor in the first tank of fuel after a davco filter change. If it does the job you will know very fast as the dead junk collects in the filter resulting in another filter change.

It could also just be soot collecting in the fuel. After my inframe my davco filters no longer turn black and the current one has over 30,000 miles and is only half way up the filter - and it's the smaller filter too.


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06-14-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #4
RE: Cm2250 Won't prime/no fuel in water separator
(06-09-2021 )Rawze Wrote:  Maybe pressurize the fuel tanks to 10 psi (via the bleeder tubes) and let it sit for an hour... see if there are any fuel line leaks. CAUTION: whatever you do ... If you have pressurized the fuel tanks up to check for leaks ... NEVER try to open the fuel caps if the tanks are pressurized. It is usually enough force to break bones in your hand or severely injure someone as the cap jumps off.

Ok, pressurized tanks for a few hours and it never dropped but 2psi and there were zero leaks. I did a laundry list of testing. I tested the fuel pressures for the gear pump and basically had nothing. So, I replaced it. It drew fuel into the separator and everything seemed good....... until today. No fuel in the separator again. Great. It has zero codes, no trouble starting and seems to run ok (other than not building enough boost and lower power). I have checked just about everything. It doesn't seem to have any air in the system. I think my next step will be to block off the ports to the separator and pull a vacuum on it to see if air is getting in it somehow.

Rail pressure isn't dropping either, its perfect.
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06-14-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #5
RE: Cm2250 Won't prime/no fuel in water separator
Maybe one of the soft fuel lines have degraded inside and there is restricted flow. My brother had a truck that acted just like that, much older though. But we replaced ALL the soft fuel lines from the tank forward and was fine again.

Also check for hairline cracks in the davco housing???


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06-15-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #6
RE: Cm2250 Won't prime/no fuel in water separator
[/quote]
no trouble starting and seems to run ok (other than not building enough boost and lower power).

Rail pressure isn't dropping either, its perfect.
[/quote]



Maybe the davco is working fine and your low boost, low power problem is something unrelated. Its not uncommon for the fuel level on a new davco filter to be very low and still work just fine.

Just a thought


User's Signature: Warranty??? Yeah right, I am the warranty!!!
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06-15-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #7
RE: Cm2250 Won't prime/no fuel in water separator
What is the filter part number you are running?
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06-15-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #8
RE: Cm2250 Won't prime/no fuel in water separator
(06-14-2021 )JMBT Wrote:  Maybe one of the soft fuel lines have degraded inside and there is restricted flow. My brother had a truck that acted just like that, much older though. But we replaced ALL the soft fuel lines from the tank forward and was fine again.

Also check for hairline cracks in the davco housing???

What soft lines?
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06-15-2021, (Subject: Cm2250 Won't prime/no fuel in water separator ) 
Post: #9
RE: Cm2250 Won't prime/no fuel in water separator
no trouble starting and seems to run ok (other than not building enough boost and lower power).

Rail pressure isn't dropping either, its perfect.
[/quote]



Maybe the davco is working fine and your low boost, low power problem is something unrelated. Its not uncommon for the fuel level on a new davco filter to be very low and still work just fine.

Just a thought
[/quote]

Yes, I have heard that as well. My low boost under heavy load and empty water separator happened together. I've always had an inch or so of fuel above the retaining ring every time I change it. Now I don't.
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