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C15 fuel bleeds back...
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bleedred
Posted 1/9/2015 15:34 (#4299768)
Subject: C15 fuel bleeds back...



East Central Ia		Have a 2001 KW T800 with a C15 and sometimes the fuel bleeds back and makes it hard to start.

It only does it when it is less than 1/2 full of fuel. Never does it when it is full.

But it does it randomly when it's less than 1/2 full.

Any ideas what to check?

Makes for a bad day when it does it and it's cold out!

Takes several 20-30 sec intervals cranking it over to get it running.
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4WD
Posted 1/9/2015 16:03 (#4299813 - in reply to #4299768)
Subject: RE: C15 fuel bleeds back...


Between Omaha and Des Moines, 7 miles South of I80

bleedred - 1/9/2015 15:34 Have a 2001 KW T800 with a C15 and sometimes the fuel bleeds back and makes it hard to start. It only does it when it is less than 1/2 full of fuel. Never does it when it is full. But it does it randomly when it's less than 1/2 full. Any ideas what to check? Makes for a bad day when it does it and it's cold out! Takes several 20-30 sec intervals cranking it over to get it running.

1: Makes sure it has a hand priming pump, on the secondary fuel filter base  = that has two additional one-way check valves inside and it helps "hold" fuel in the system.

2: Change your fuel return check valve, and don't overtighten the new one; needs only to be snug.(red arrow)

3: Some worn fuel transfer pumps (lift pump) can allow a small amount of air, to get into the fuel system, thus allows the fuel to possibly drain back to the tank and that creates an air pocket, which makes the "next start-up" hard to get fuel pressure built up to help injectors fire. (you need quite a few "test sight glasses" to actually t/s this exact problem, and let engine set over night) You may just want to install a new one, verses paying for mechanics time and trouble-shooting dollars, if doing your own repair = that's your call

4: Sucking air somewhere = need to get test equipment, on engine and troubleshoot. (Small possibility of injector seal problems and seating problems, too, but this are rare) Again, a number of fuel sight glasses help find the problem and fuel pressure gauge/s.



Edited by 4WD 1/9/2015 16:14




(Later 3406E _C-15 fuel filter base design_right photo_in paint program.jpg)



Attachments
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Attachments Later 3406E _C-15 fuel filter base design_right photo_in paint program.jpg (34KB - 895 downloads)
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Corn Field Cadillac
Posted 1/9/2015 16:54 (#4299898 - in reply to #4299768)
Subject: Put a "loop" in your new fuel return to tank


Center of the Universe, Huron County, Ontario. Can		It will prevent fuel from siphoning back to tank,
Just make sure the new line back to tank is a couple feet longer.
Poor mans check valve, NEVER fails as nothing to fail.

Good luck
Chris
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bleedred
Posted 1/9/2015 17:50 (#4300016 - in reply to #4299813)
Subject: RE: C15 fuel bleeds back...



East Central Ia		Thanks for the info. Looks like the fuel return check valve is a good place to start.

We do have the hand priming pump. Question on that... I tried to hand pump it to help prime it to get it started and you have to pull it out and hold it or or sucks back in. Just like filling a syringe. It creates a lot of suction and you have hold it for 3-5 secs and then push it in.

The other ones I have done this on you could just pump away.
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bleedred
Posted 1/9/2015 17:52 (#4300025 - in reply to #4299898)
Subject: RE: Put a "loop" in your new fuel return to tank



East Central Ia		I am not following you here. Put a loop in the fuel return line where at?
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4WD
Posted 1/9/2015 19:16 (#4300311 - in reply to #4300016)
Subject: RE: C15 fuel bleeds back...


Between Omaha and Des Moines, 7 miles South of I80

bleedred - 1/9/2015 17:50 Thanks for the info. Looks like the fuel return check valve is a good place to start. We do have the hand priming pump.

 Question on that... I tried to hand pump it to help prime it to get it started and you have to pull it out and hold it or or sucks back in. Just like filling a syringe. It creates a lot of suction and you have hold it for 3-5 secs and then push it in.

The other ones I have done this on you could just pump away.

 

That is usually a sign of a restriction somewhere, or it could be that one of the one-way hand pump check valves, has come loose and flipped over. (See photo, for correct view = one check valve is pressed in , in one direction; and the other check valve is opposite. Note: Flow would enter the right side check valve, in this photo; then exit the left side.)

Was the truck outside, with cold fuel{gelling}, or older fuel filters (= more restriction, right there, than Summertime) Was -12F just the other night, here.





(CAT fuel hand priming pump_check valves_in paint program.jpg)



(3406E fuel filter base_with red line casting.jpg)



Attachments
----------------
Attachments CAT fuel hand priming pump_check valves_in paint program.jpg (40KB - 886 downloads)
Attachments 3406E fuel filter base_with red line casting.jpg (31KB - 818 downloads)
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bleedred
Posted 1/9/2015 19:38 (#4300364 - in reply to #4300311)
Subject: RE: C15 fuel bleeds back...



East Central Ia		No it's been sitting in my heated shop since before Christmas.

I needed to move it but it didn't want to start.

I'll look at your pics on my computer but that might be a good place to start.

The truck runs fine and doesn't seem short on power. If it has a restriction wouldn't it lose power?

We had a heated see through type filter installed before the secondary filter last year and it has a Che I valve so we were hoping that would help our problem but it has not.

So I wonder if we don't have a problem in that hand pump assembly.
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Corn Field Cadillac
Posted 1/9/2015 19:44 (#4300377 - in reply to #4300025)
Subject: RE: Put a "loop" in your new fuel return to tank


Center of the Universe, Huron County, Ontario. Can		4wd seems to be on top of this,
I'm speaking from Detroit Diesel experience.
There's a line that returns from back of head to tank.
That Line had a restrictor fitting in it,,later ones a check valve.
To prevent fuel draining back to tank.

You can do the same with a longer hose ,
Wrap it in a loop,so it acts like a trap beneath your sink.
Will always have fuel in it and can not siphon back to tank.

My 2 cents

I'd pay more heed to 4wd though, he has some great insight.
Well done,

Thanks
Chris
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catmendoo
Posted 1/9/2015 23:21 (#4300820 - in reply to #4300377)
Subject: RE: Put a "loop" in your new fuel return to tank


Northern edge Mahnomen County		I'm not sure if truck engines are the same as tractor engines, I have a tractor with C15. In between the fuel/water separator and the fuel pump there is steel line. This line is held to the block with a clamp that wraps around it. Vibrations wore a hole through the line inside this clamp. It never leaked fuel out, but it allowed air in.
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