Cummins 6bt wont get up to WOT after fuel line blockage

[Joseph Byrne]

Hi All

i just got the motor (Cummins 6bt 250hp) running after a fuel blockage (massive build up of gunk in the fuel line and the primary fuel filters).

I primed the system and got fuel going through, cracked the injectors and waited for the bubbles to stop.

just took it out for a quick run to see how it was going and it runs smoothly and is smoking a lot less than it was! But won’t rev past 2200 RPM 

Any ideas? 

Topic

[Rob Schepis]

Leave the fuel fill caps off when introducing air pressure into the fuel lines.

You should remove the fuel pickups and check the tubes for clogged screens, etc.  Any screens on fuel pickups are bad, you want the pickups to act like vacuums and allow the filtration system to get the junk and filter it out.  Therefore, pickups should be large diameter and very close to the bottom of the tank.

[Joseph Byrne]

I had a quick look in the tank through the small sender unit hole and it looks reasonably clean.

it does have a couple of baffles in it and I can’t see the fuel pickup. <br />I have the professional tank cleaning guys coming to have a look and give me a quote to clean it and as part of that add in an inspection port.

I’m also heading up to the boat tomorrow to blow out the lines including the return line this time and check the filters again, maybe look at replacing the old fuel lines while I’m at it

 

[pwrobert]

What is your fuel tank made of? Does it have a clean-out port?  If not consider installing one in the most accessible place in the section that has the fuel pickup. Likely you can’t get directly to all areas because of baffles but if you make a 6 inch opening you can likely direct some jetted fuel or scrubbers through some of the holes at the bottom of the baffles. <br />even with scrubbing the bottom of the tank there will likely be some gunk clinging to baffles. But since the issue came up when the level got lower most will be below that level. When fuel sloshes in a partially filled tank the greatest agitation is in the top few inches of liquid. Think of waves on the surface not doing much to divers. <br />anyway you don’t have to get at the whole tank but using a fuel polisher for a while would be good. Best to only put In a few gallons and run in some rough water on purpose and keep a eye on the vacuum gauges. first sign of it getting in the yellow – stop and change them and repeat until everything is good for a reasonable interval.  pita. But better when your under control and not when cruising.   Been there done that. 

[Joseph Byrne]

I didn’t clean out the tanks, I have a fuel filter system running between the tanks and the engine filter.

I did put a diesel bug killing additive in but I’m guessing that’s not going to be enough.

one other thing is the fuel lines are old copper lines, thinking it would be wise if I replaced these with new ?

 

[donald roth]

Have you cleaned the tanks?  Thats where the crud is coming from, your efforts will be futile until the tanks are clean, or you install a filtration system that has a high enough capacity to accomplish that, and a water separator. 

[Joseph Byrne]

Hi Tony

it was running fine until we came back in some rough ish seas with only 200l of diesel left in the tanks and I think it sucked all the gunk up from the bottom. Maybe had 15-20 minutes running in that rough.

I don’t have the last chance filter anymore, I threw it away. I look in it and the fuel was clean. The fuel in the first filters was black with gunge, the fuel looked like old oil 

 

[Tony Athens]

Not making RPM?

Exactly how long was it “BEFORE”?   

Did you cut open the old “last chance fuel filter to “see” what was in it?  May you stll have in in the trash can?

[Joseph Byrne]

Hi Rob

i blew back through the main line but didn’t blow back through the return line.

filter on the engine itself was totally clean but I replaced it anyway.

never had a problem before this getting to WOT of 2600rpm

i also added a fuel treatment to the tank and filled it up with fresh diesel

[Rob Schepis]

How about the on engine filter?  

Did you back flush ALL of the lines back to the tank?

Is this the first time you every had an RPM issue?  What was max RPM before the fuel issue?

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