Engine Idle Rolling

CaptDave

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Well, some days are better than others, engine has had a slight rolling recently at idle and the other day got worse. Changed fuel filters to eliminate the possibility of not getting enough fuel and low and behold no change. Mechanic says it sounds like the fuel injection pump is going and found out there is no buffer spring inside pump to adjust. Could be a two to three thousand dollar repair and now whoever purchases the boat will get a newly rebuilt fuel pump. Oh well, part of owning a DE boat with a diesel engine. I can not complain because the John Deere 6076 AFM30 has trated me well.

Dave
 

Beamie

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Dave,

When you say rolling are you saying hunting? Is this just at idle? Warm or cold engine or both times? Is the fuel position on the rack (throttle) at the pump changing position when this is happening or is it steady?
 

captainlarry84

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Try a good double dose of a quality fuel conditioner. It could be fuel related if it just started to happen. What was the condition of the old fuel filters? Did you open them up to see? Also if it is fuel related maybe top off with fresh clean graded A diesel. Does it also happen on either tank or just one tank? Is it also possible that a little water got by the filters and it is laying in the injector pump? I would not be so sure on the pump going based on the problem. Lastly what are the idle specs? Is your boat idling at less than 50 RPMs below spec? If so that will make the motor hunt.
 

CaptDave

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It has been a slow roll for a while at an idle but now is doing it all the way to 1000 RPMs. The pump is coming off and headed to the shop for an inspection. The filters were changed and including the two after the primary. The fuel was purchased at our marina where we have had no issues with it this season. They have a brand new above ground tank and just started pumping diesel this summer. I want to make sure whoever purchases the boat has no issues with the boat. I know this is not the easy or cheap way out but at least we will have a much better idea if something internally in the pump is wrong.

John and Larry, thanks for your response.

Respectfully,

Dave
 

Fechmup

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I have a JD 6076 in a 32' Carolina built hull and my motor will "lug" in gear unless I give the throttle a little touch. I'm thinking you're describing something a little different with roooolllllllinnngggg, but I'm curious if I have a similar situation. I look forward to an update.

Thanks,
Kevin
 

CEShawn

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Dave, atleast you dont have TWINS, wondering when the other shoe will fall...
 

samhop

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Dave
before you look at the fuel rack, take some more time noodling.

check your fuel return flow i dont know what it should be for your JD but its a constant to rpm, so if you are idling at 6500rpm no lode your fuel pump should return X gpm, a JD service rep should be able to give you an idea. so if the rep tells you your eng. should return 1/2 gpm and your getting 1/4 you got a flow issue.

if your using a racor filter, brake it down and make sure the float ball and water spinner are clear. you would be amazed at how much mung can build up there. i have seen 1000hp shut down while towing, stopped by mung in the racor Assembly, not the filter.

after braking down cleaning and reassembling your racor, assuming your using that filter system. if you still have a flow issue think about your fuel lines. or plugged stinger - pickup. if your stinger is clear run a new temporary hose from pickup to filter. old fuel lines brake down and collapse internally so the line looks ok but the liner in the fuel line separate and blocks the line often only one way like a check valve.

if you have been running your fuel system for a long time with a air leek or restricted fuel flow or run dry often or have over 10,000 hr on the rack and have checked all above, then get the rack looked at.

hope that helps im sure others that run that eng. will also have insight
jest a little diesel deaf A

sam
 

Brooksie

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Dave
before you look at the fuel rack, take some more time noodling.

check your fuel return flow i dont know what it should be for your JD but its a constant to rpm, so if you are idling at 6500rpm no lode your fuel pump should return X gpm, a JD service rep should be able to give you an idea. so if the rep tells you your eng. should return 1/2 gpm and your getting 1/4 you got a flow issue.

if your using a racor filter, brake it down and make sure the float ball and water spinner are clear. you would be amazed at how much mung can build up there. i have seen 1000hp shut down while towing, stopped by mung in the racor Assembly, not the filter.

after braking down cleaning and reassembling your racor, assuming your using that filter system. if you still have a flow issue think about your fuel lines. or plugged stinger - pickup. if your stinger is clear run a new temporary hose from pickup to filter. old fuel lines brake down and collapse internally so the line looks ok but the liner in the fuel line separate and blocks the line often only one way like a check valve.

if you have been running your fuel system for a long time with a air leek or restricted fuel flow or run dry often or have over 10,000 hr on the rack and have checked all above, then get the rack looked at.

hope that helps im sure others that run that eng. will also have insight
jest a little diesel deaf A

sam

You are right, the Racors have some tricky right angle passages in them. It don't think partial fuel blockage would effect idle though, it would only starve at load condition. One time I got a set of injectors back from the injector shop, all new nozzles they claimed, the engine loped (rolled) like mad. Took them out and back, this time watched while they pop tested them, one seemed very different spray pattern, come to find out, they had installed wrong # nozzel in one. Moral= bad injector can cause loping too.
 

samhop

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fwiw
"It don't think partial fuel blockage would effect idle though, it would only starve at load condition."

from my experience that statement is not true.

i have rolling and missing that smoothed out with increased rpm, as a result of plugged racor at the float. and i have seen bad lines that will flow with a pump on them but will not siphon.

cleaning a filter assembly and checking stinger and lines is way cheaper than getting a rack overhauled. if your fuel supply checks out definitely pull your injectors an have them tested.

this is what can happen IMG_0971.jpg if you run a bad injector to long

IMG_0971.jpg
 

traditions

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You need to adjust the buffer screw on the injection pump.If you have a mechanic that is going to remove the pump for inspection and doesn't know how to adjust the buffer ,than I suggest that you find another mechanic.The 300 deeres have a tendancy to roll and are hard to adjust,One that we had was hard to stop the roll,you could make it stop at idle and when you put it in gear and the load was on,like the hauler engaged at idle it would roll,and was hard to adjust.This can be remedied by raising the idle a little higher when adjusting the buffer.Both adjustments are double nuts on the back end of the pump.We tried to keep the idle speed a little lower than the manual suggest ,for hauling reasons ,and when the idle is low,say 650 or so ,its hard to stop the roll.I think the manual wants the idle at 800.
 

CEShawn

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I was having RPM issues this year. So I decided to put in Seaboard Marine's unit and was very happy with it. I had the guy running my boat saving the Racors and they didnt seemed so fouled. I looked in the bottom of the bowl and only saw a little bit of stuff. When I totally drained the unit and took it down it was CLOGGED SOLID with this crap.

I'm very happy with my bulk filter from Seaboard.

1. Next year I am going to redo my fuel lines and filter placement to put them in the cabin to be easier to change.

2. I am still going to keep the Racor filter and might put a bypass on my main filter set with another SB marine filter. Of course the only filter problem I had in 450 hours since my filter change was coming back into the harbor at midnight blowing SW.

3. Going to put something different on my generator than the small Racor.

photo (36).JPG
 

traditions

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You cant blame that shit on the racor.It did what it was designed to do.When you plug up them spin on filters they will bypass and you will have a real mess on your hands.What you have there is a bad case of algae caused by water in your tanks.
 

CEShawn

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Yup, worse case I ever had just taking the boat over. Then I think once the heat came it came out of hand. I think I have it nailed now, again 450+ hours without any problems...

I think its because I was keeping my tank pretty low for such a long time until I started doing offshore trips. But I honestly am not sure if condensation for half a summer can do that, that I dont know...
 

traditions

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We have a lot of algae here in midcoast Maine.I don't think it matters if the tank is full or not.The tanks that are on deck,under the stern seem to be the worst.The fuel we get is dirty and troublesome to say the least.I use a FPPF fuel power treatment to disperse water and it seems to do the job.The racors with out the heat shield have the drain glued into the bowl and are impossible to drain.The spin on from out west is kind of what was on my Deere from the factory,but I also had a racor ahead of it.It had a small aluminum bowl for water to collect,but no water ever got past the Racor.
 

Fishinengineer

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Shawn, when you get back on your ship order a 25liter pail of the Drew Amerstat (biobor). Fill up a few sample bottles and bring them home. Two ozs treats about 300gals. When you finally kill those little critters is when the real fun starts, have plenty of spare filters on hand. Get rid of the diesel clap.
 

CEShawn

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Ha! Imagine the damage would do to your luggage? We use Drew all the time but not taking it home. I used this and it solved the problem.

image.jpg
 
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