Can’t get yanmar 3GMF above 2200 rpm under load question

Jan 24, 2017
666
Hunter 34 Toms River Nj
Spoke to a diesel mechanic and he has given me a list of things to check
He is 85 percent sure that it is a fuel issue and not mechanical

Non mechanical:
1. Fuel return from transfer pump, fuel flow.
2. He thinks that with the low sulfur fuel that the fuel lines could be bad.(partially clogged, inner core breaking down)
3. Clogged pick up tube.
The fuel lines are thirty eight years old, so I’m going to change them regardless.

Mechanical:
Bad fuel pump
Governor
Things he didn’t think it was
injectors
compression issues
mixing elbow
Going to do some hopefully quick easy fixes and hopefully they fix the issue.

Thanks for all the suggestions
 
May 24, 2004
7,129
CC 30 South Florida
I agree with his theory about clogged filters causing low power issues, but I’m having a hard time wrapping my head around both filters clogging with less then 20 hours, and when I emptied my fuel tank and refilled it the old fuel and new fuel was clean.
I have seen a Racor filter clog within one hour with water and sediment. In 20 hours things can happen. Just drain the water separator and inspect the filter cartridge . Check the Microns size on that cartridge; the use of 2Micron cartridges quite often result in constrained fuel flow if there is sediment in the tank. It is also redundant as the secondary filter is usually a 2 Micron to get the smaller particles. Recommend the use of a 10 micron for the Primary filter. Check the vent to the fuel tank, sometimes critters nest in there and block the free flow of air needed. You may also check the fuel flow at the lift pump, a perforated diaphragm may reduce fuel flow. Check for any fuel leaks at the pump or fuel lines. Wherever fuel leaks out, air can leak in and air can cushion and reduce fuel pressure. It can sometimes be hard to properly bleed the air out of the fuel lines in these Yanmar engines, air can get trapped, so repeating the procedure a couple of times sometimes is necessary. You may also turn the Prop shaft by hand to see if turns smoothly or if an undue resistance is present. Lastly start the engine and remove the oil cap, hover your hand over the opening and feel the back pressure, it should be a steady tapping feel but if you feel hard thumps it means excessive compression is being lost as it blows by the piston rings. Sometimes the use of too thin a motor oil can cause blow-by, in contrast using a thicker SAE oil can usually increase the compression of a tired engine. I suggested it before, check the valves lash as it will affect compression. Check the air intake tube and air filter for obstruction or clogging. Do not discount anything even though you may feel they should be good, go back to the mixing elbow, filters, linkages etc. until you find the culprit.
 
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Jun 15, 2012
694
BAVARIA C57 Greenport, NY
Make up a test diesel fuel supply consisting of 1 gallon jug, fitting, clear fuel filter and hose. Hang jug above engine. Connect directly to fuel inlet on injector pump and let gravity feed. Now when you run engine you have completely eliminated fuel supply as source of problem.
 
Jan 24, 2017
666
Hunter 34 Toms River Nj
got onto the boat today to do some of suggestions from the group.
1. got rpms to about 2600 in neutral still not great and rpms in gear 2200.
2. Removed fuel discharge return line from last injector back to the fuel tank and basically no fuel flow, only a few drops. Diesel mechanic said I should have a steady flow back to the fuel tank.:huh:problem
So fuel circulation issue appears to be the problem.
3. checked for fuel from tank to fuel feed lift pump and all appears good.
4. Checked all bleed points to the injectors including the nozzle body and all appear to get fuel.
5. Checked the top nozzle spring nut and got
NO Fuel. Problem!:huh:

Fuel in tank appears goodpicked up some fuel from bottom of tank all clear no sediment.
Replacing all fuel lines because they are 38 years old and even if they are still good, I’m going to replace all of them just to eliminate possible issue.
Replacing primary and secondary filters even though they have less then 20 hrs on them, again to eliminate possible issue.
Plan to rig a external fuel can with new diesel and run it to primary filter.
If the issue still exists.

diesel mechanic suggested replacing the fuel feed lift pump. He said that inside the pump is a diaphragm that may have started to fail. If it has not completely failed he believes that it will produce enough fuel to the injection pump to allow the injection pump to operate enough for the engine to run however not supply sufficient fuel to get to the correct rpms under load. Therefore starving the engine of fuel to the injectors.

hopefully this works
 
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Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
Number "3" how did you check?
A negative pressure would indicate m a clogged pickup tube screen, you can blow through it and maybe loosen the stuff that's coating the bottom of it but it probably will return. see if you can remove the pickup tube to physically check (if you haven't already) but it looks like you're getting close to solving the problem!
 
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Nov 22, 2011
1,192
Ericson 26-2 San Pedro, CA
Number "3" how did you check?
A negative pressure would indicate m a clogged pickup tube screen, you can blow through it and maybe loosen the stuff that's coating the bottom of it but it probably will return. see if you can remove the pickup tube to physically check (if you haven't already) but it looks like you're getting close to solving the problem!
Or, he could have done what I suggested and purchased a small plastic gas can at Home Depot or Pep Boys for ~$15 to use as a temporary tank, together with two pieces of new fuel hose (one for pickup and the other for return), and bypass the tank and the pickup tube altogether. As it is, I think it's dubious that he has truly eliminated all the possible issues with step 3.
 
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Jan 24, 2017
666
Hunter 34 Toms River Nj
clear ridged tube into the tank until it bottomed out to pull a sample out from the bottom. Looks good. Can’t get the pickup tube out of the tank yet, corrosion on the fitting, letting some pb blaster soak on it for a day or two before attempting to remove it. Don’t want to break it off or damage the tank. If that doesn’t work, I’ll try a little antifreeze coolant on it. That’s always worked on really seized fittings before.
 
Feb 14, 2014
7,400
Hunter 430 Waveland, MS
I’ll try a little antifreeze coolant on it. That’s always worked on really seized fittings before.
Brake fluid works too and rated #2 in a test.

There was a test using many fluids to release corrosion. This was number #1
41dR99ShHhS._AC_.jpg

PB Blaster was 4th.
Jim...
 
Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
Or, he could have done what I suggested and purchased a small plastic gas can at Home Depot or Pep Boys for ~$15 to use as a temporary tank, together with two pieces of new fuel hose (one for pickup and the other for return), and bypass the tank and the pickup tube altogether. As it is, I think it's dubious that he has truly eliminated all the possible issues with step 3.
And for this you quoted me?
It's called a day tank and I just happen to know what you're talking about :biggrin: but he wants to troubleshoot his fuel system either way. Maybe you should quote some other people giving advice too because they may feel left out...
 
Nov 22, 2011
1,192
Ericson 26-2 San Pedro, CA
And for this you quoted me?
It's called a day tank and I just happen to know what you're talking about :biggrin: but he wants to troubleshoot his fuel system either way. Maybe you should quote some other people giving advice too because they may feel left out...
Sorry you took offense at this. None was intended.

I chimed in in relation to your post because it seemed to me that he really did not check point #3. (You question: "Number 3, how did you check?") My comment was not aimed at your advice--which seems just fine to me, by the way--but was more of a query as to why the OP (or anyone) who was troubleshooting a problem with the pickup tube, tank, and so forth wouldn't try the day tank route first as a cheap, simple, and possibly highly effective troubleshooting tool. That completely takes the tank and all associated plumbing out of the circuit, which makes sense as the first thing to try--to me, at least.

At any rate, as far as I can tell, it does not seem as though he has eliminated Step 3 as a potential problem.
 
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Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
No offense really it's just comical to me that almost always I'm the only one that gets quoted on these discussions, my boat is probably going have in the same problems it's a1986 H34. First issue is to deal with the forward aft bulkhead underneath the cockpit because no matter how I try it's going to be very painful for me to crawl in to the lazarette.
I can't imagine any old fuel tank not having sludge in it, been there done that with my Oday 30,
 
Nov 22, 2011
1,192
Ericson 26-2 San Pedro, CA
No offense really it's just comical to me that almost always I'm the only one that gets quoted on these discussions, my boat is probably going have in the same problems it's a1986 H34. First issue is to deal with the forward aft bulkhead underneath the cockpit because no matter how I try it's going to be very painful for me to crawl in to the lazarette.
I can't imagine any old fuel tank not having sludge in it, been there done that with my Oday 30,
I appreciate your graciousness, Denise.

Yeah, old fuel tanks do get sludge. But for whatever reason I haven't had that problem--yet--in my 1984 Ericson, even though it's the original tank, i.e., 37 years old! I do treat the fuel with biocide consistently, but who knows what the previous owners did or did not do? My fuel filters always come out really clean, but I still change them every so often "just because." I'm surprised by that, really, but not complaining!
 
May 24, 2004
7,129
CC 30 South Florida
Guys, we all post here, giving our ideas and recommendations with the best intentions, the questioner is free to use those those recommendations he may think are best. Unless the suggestion is something that may cause damage or dangerous no need to criticize or comment on others.
 
Jan 24, 2017
666
Hunter 34 Toms River Nj
Ran engine with new fuel lines and bypassed the fuel tank, changed both primary raycor and secondary filters. Both appeared to be clean. Still cannot get above 2200 rpm under load. Fuel pump should arrive tomorrow, and that is the next item on the list to replace. So far I have now been able to eliminate problem with fuel lines and clogged filters. Also read somewhere about a little ball check valve inside the housing of the raycor inlet could be stuck.
hopefully the new fuel pump will be the answer.
 
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Jan 7, 2011
4,727
Oday 322 East Chicago, IN
Some one (moderator) should have combined these 2 parallel threads (this one and the one in Engines and Propulsion)…

Greg
 
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Jan 24, 2017
666
Hunter 34 Toms River Nj
as you guys had asked about how I checked fuel tank and pick up tube, I still have not been able to get pick up tube removed yet due to corrosion. Pulled fuel from the pick up tube directly and by sticking a clear tube though the vent fitting into the bottom of fuel tank multiple times. All appears to be good.

I did set up a two gallon day tank as suggested with temporary new fuel lines. This test eliminates any possibility of fuel tank and fuel lines being the issue, which was a great suggestion. Going to replace fuel pump tomorrow and if all goes well, hopefully this will correct the problem :huh:
 
Jan 24, 2017
666
Hunter 34 Toms River Nj
replace fuel left pump with new one, still no difference :banghead:
Spoke to yanmar technician at Mac boring today and they suggested to look at an issue with the governor. They said that a bad injector could be a cause however they said that most like the engine would run rough and most likely smoke. I concur about injectors not being the issue.

Still could be the fuel injection pump,
Hopefully not, out of stock and has to be special ordered. List price was about $1,300 :yikes: Plus shipping !! They also said that my fuel return will not be a stream as I thought it should be, but more like a trickle. That is something that I have to look into again, as I was looking for a steady stream. Anyway going back to look into any adjustments that can easily be made on the governor this weekend. Unfortunately the boat is being hauled so for the winter layup, and running out of time before I have to winterize the engine.

looking like another spring project headache :banghead: