How do I Clean Hunter 49 Fuel Tank, or the Fuel.

[ice breaker]

I had a problem once where the 90 degree barbed fittings that connect to the fuel lines got stuffed with the thick paper like bug stuff. I needed to use a strong wire to ream out the fittings. After that all worked well. On our 41 there were several barbed fittings on the pickup side including on the racor filter body. You may want to check them all.

As a side note, my genset was running fine too while I was doing this trouble shooting.

 

[jssailem]

You are on a reasonable path. Diesel engines need clean fuel, clean air, and compression to run.

Addressing Fuel

• You cleaned the fuel and fuel tank
• You replaced fuel lines
• Replaced fuel filter
• You found what you called white knobby stuff in the tank. Did you check all of the fittings to be sure no knobby things are caught in the 90 degree fittings? I found some in the inlet to my Racor. It floated in the fuel line intermittently blocking the line at the fitting

Compression

• The engine runs so I am ruling it out as ok

Air

• Clean filter?
• Clean air intake?

Hope this helps.

 

[senang]

Checkout this issue with the Racor filter HOUSING getting clogged.

Beware the check ball valve on your Racor! - Cruisers & Sailing Forums

Just a friendly post here to warn any who don't know about the wee little gremlin in your Racor filters that can shut your diesel down cold. I had my engine die in the Straits of Georgia , British

www.cruisersforum.com

Otherwise start your engine from clean fuel in jerrycan connected directly to Yanmar on engine secondary fuel filter (bypass Racor).

 

[Screen Saver]

Yes I am aware of the check valve . I bought a whole new Racor assembly & filaments recently in trying to resolve this problem and for a number of other reasons. One of those reasons was so I could remove the check valve and run that Racor in reverse via a lift pump, to effectively see how much the filter has collected by backwashing the filter, and to see how effective backwashing is.

As of yesterday Im changing my focus and pretending this is a new problem, starting from scratch, partly because the symptoms have changed a little, from originally stopping within 10min of getting fuel, to now running just fine for at least 2 hours and up to about 3 hours. I have been keeping a log with dates and times, filters are all numbered etc, and in reviewing my log, somewhere along the way after the very first filter change which was old past due etc, the motor then continued for 2-3 hours, also it went from stumbling and missing at the 2-3hour mark on for sometimes another hour, to now, as soon as it starts to stumble it will stop within the next 2-10 minutes.
Yesterday I decided to switch over to the new Racor assembly which has its own pickup and return point on the tank and try my last new filter. At least this will eliminate everything from and including the tank pickup, elbows, cut off valves etc, the hose from there to the engine is new. When I removed the engine return hose from the tank a quite long puff of air came out of the tank, so the tank was positively pressurized. How it got in that state is one question, I would expect if anything it would be negative/vacuum, and obviously this suggests there is a restriction in breather.

So next time I run the engine and it starts to stop, I will remove the fuel cap, thus proving the breather theory.
I will also measure the L/hr coming back through the return to the tank, when the engine is running fine, and when not.

Still I need to logically connect these dots and I am unable to link these
If pump the primer knob on top of the engines Yanmar filter, the motor regains any lost rev’s and cease’s to stumble
It has always started in 1-2 seconds, now takes 10-15 and winds its way up to idle
Why does it run fine for 2-3hours, how can this be a restriction in the supply.

 

[SycloneDriver]

My thoughts are:
1. Blocked tank vent.
2. Air leak.
3. Bad lift pump.

A blocked tank vent would starve the motor faster with more fuel in the tank. Sound familiar?

 

[jssailem]

. Blocked tank vent.

This could pressurize the tank. While your pump is emptying the tank delivering fuel to the engine, the fuel return lines are returning fuel to the tank. This is one of the ways the fuel remains cool. It could be possible to have more fuel going bak than is being consumed in the engine.

 

[Screen Saver]

Yesterday I measured the how many L/hr were being returned to the tank as in when the engine is working normally.
To my surprise about 60L/hr are going back to the tank at idle and at 1500 about 75L/hr So clearly the system can supply a lot of fuel.
Having now cleaned up the breather Im on another 4 hr run right now so if ( or I should say when) it stops I will remove the fuel filler cap, to confirm no breather restrictions and assuming that doesn't help I will measure the return L/hr again.
If the L/hr on the return side are much the same and its still stopping then as far as I can see it must be inside the injector pump assembly, which requires more skills and tools than I have as far as I know.
I can not possibly see the engine requiring a flow rate of more than 60-70L/hr through the system.

PS what did concern me a little was on measuring the return L/hr, there were very fine signs of air bubbles, perhaps smaller than a pin head. Im not sure if this is normal or not and perhaps as a result of injector pump compressing the diesel, for injecting pressure purposes. It as running fine at the time, but I don't know if its normal and not something generally people look at. I have been around every connection I can find multiple times

 

[jssailem]

I have not seen the bubbles, I have read about diesel foaming when under pressure. This is to be avoided. Would be a problem is the foam was near your fuel intake as in low fuel in the tank. With adequate fuel the foam should dissipate and you should draw in normal fuel. We have a few fuel specialists here on the forum. Perhaps one of them will share their insight regarding the bubbles or foam appearing in diesel.

 

[SycloneDriver]

A few years ago a coworker had a Cummins generator that had difficulty starting. I replaced the fuel return line with a section of clear vinyl hose. I was surprised the fuel being returned to the tank was extremely foamy. I noticed that the foam returned to solid fuel after traveling down the hose about 5 feet. I figured that might be an important clue. I thought the fuel must be cavitating inside the injector pump and then returning to liquid after exiting the injector pump. There was plenty of volume returning to the tank. I replaced the lift pump and the foam and starting issue disappeared.

It sounds like you may have solved your issue if its ran for 4 hours.

 

[Tally Ho]

So here is a rather long update as problem goes on:
Yanmar 4JH4-TE. Fuel issues. I admit Im not sure what to do next. Here is a summary

When did it start: Right after (10min) taking on a new load of fuel some 400L
Symptoms: Fuel starvation, it will start to stumble, miss a beat or two, gets slowly worse, revs drop, eventually it stalls. It used to start almost instantly, now its slow and you must grind for 10 seconds and it gradually winds its way into life.
Assumed cause: Bad fuel, or dirty filter, or sediment disturbed from filling process, clogging the filter.

Relevant information: The Hunter 49 has one fuel tank with multiple pickups, for Main engine, genset, & auxiliary. The genset is using the same fuel tank and its own filter has not missed a beat, and is running now as I right this.

What I have done:
Initially I replaced the external Racor filter, which was old, before replacement of this filter and after the fueling the engine would run maybe 10minuts and after the new filter it would last about 3 hours before the symptoms return

Then I replaced the Yanmar filter on the Engine, this made no difference

I decided it had to be bad fuel dirty fuel, so I bought a highspeed transfer pump and hoses, sucked some 500L out as quick as I could hopefully taking some dirt with it and then let it sit. Mean time as best I could through the fuel sender whole I cleaned out the tank and looked around with mirrors, pushed nice white microfiber cloth all around inside on a wire. The tank itself looked pretty clean to me. On the very bottom where it took the last bit of fuel out there was a small dirty track and three sticky knobs about the size of cigarette butt (which I understand is the fuel bug), the rest of the tank was brilliant white and clean

I bought an expensive Yanmar lift pump and put 80% of the fuel back via the yanmar lift pump and a new 30 micron Racor filter assembly. Not one drop went back into the tank that did not go through the 30 micron filter. I also replace the racor filter again . so Now I should have clean fuel, clean tank and another new filter was used. No change, didn’t fix it.


I bought another Racor Filter Assembly complete and ran that to the Yanmar lift pump I bought, with the output of lift pump going back to the return to the tank. Effectively fuel polishing. I ran this 24hrs putting about 1200 odd liters through the system.

In desperation I replaced the rubber fuel lines tank to filter, to Yanmar. ( didn’t replace the return) … no improvement.

I tested and measured how much fuel can the lift pump suck through the Racor. The filter that I used to put the fuel from my storage drums back into the tank, was pumping 1 liter every 72 seconds when I started and at the end 1L ever 2 ½ min, so from this I deduced the filter was doing its job and the fuel was indeed bad.

I then inserted my lift pump between the Racor and the Yanmar fuel line, to help it get fuel. So with a new filter and the lift pump, roughly capable of feeding my engine 1L 72 seconds (approx. 50L/hr) that should be more than enough.

Off course each time I opened any fuel connecting points I bleed both racor and yanmar, and keep in mind I have never ever until now had to bleed any of my fuel lines. But to be sure I did it anyway.

I then moved the pickup point of my Yanmar to connection point for the genset which did not help.

So now perhaps with tunnel vison as I have been on this over a month now. I see no other choice but to have two problems.
Given it started with 10min of fueling, and the fact that the filter used to put back the fuel into my tank could only pass fuel at half the rate it started with, I conclude the fuel was bad.

However moving on, given the fuel has all been through a 30 Micron filter, and the current filter on the engine ( that is still stopping) is passing fuel at the rate of a new filter, and I have added a lift pump it never had before, this must be a secondary problem within the very expensive and complicated Yanmar injector pump.??

The problem I have with this deduction, is it assumes two problems, or one caused the other, ie dirty fuel and bad Yanmar injector pump. Plus from cold (ok 30c) start in the morning, it will typically run fine for maybe 3 hours at 1500 and has no trouble (in this period) going to 2500 (9knts) The engine is well up to temperature in the first 10-20 min. So how come it runs for 2 or 3 hours. This is not typical of a mechanical problem

I am not sure I fully understand, but if you say that the engine will run for several hours before having fuel issues, it COULD be a blocked vent line…after a while, you get a vacuum in the tank that the fuel pump cannot overcome.

It could, after sitting for a while, relieve the vacuum, allow the engine to run again…until the vacuum once again gets too strong.

Why would the generator not suffer the same fate…? Well, maybe the fuel consumption rate is less than the auxiliar, so it doesn’t generate the same vacuum (or it takes longer). Or maybe you are not running the genny for hours.

I once had what seemed like an intermittent fuel problem on my John Deere tractor. I could run it hard for about 1 hour, and then it would die out…a definite fuel starvation issue. When it first happened, I pulled the fuel filter and opened the tank. Put it back together and it ran fine for another 30 minutes until I was done cutting the grass.

A few weeks later, same thing happened, but this time I realized that when I pulled the fuel filter, fuel was being pulled back into the tank…by a vacuum.

The tank cap is vented, to prevent a vacuum, but mine was plugged up. So, cleaned the vent hole, and have not had a problem since.

Maybe I have not understood the current state of the engine, but if it runs fine for a while, and then dies, I woukd check for a plugged vent.

Greg

 

[Screen Saver]

Guys thanks for the thoughts much of it is good new ground:
Basically any restrictions in the vent have not solved this. My trip yesterday, the motor again stopped between the 3 and 4 hour mark..
To be sure it was not tank or vacuum pressure related I then removed the tanks filler cap and there were no obvious signs of either pressure or vacuum., and with the filler cap off it did not help. Once this problem starts after the 3 or 4 hour mark it gets progressively worse, running maybe 1 hour if your lucky then 30 min till eventually you get down to only a few minutes. How in every case, pumping the primer pump on the engine if you get to it quick enough spurs the engine back into life.

The comment about why the genset keeps going is probably true, it would never have been run for 3 hours continuously and would consume less fuel., so as suggested this is probably why it keeps going. I have not looked at the genset return, either volume or bubbles, so I will try to run this test as well.

The comment about foaming is new and could well fit, and I will investigate this. The reason I like this concept is it could explain the 3-4 hours, possibly from the small bubbles I see in the return.. Where I saw the bubles was as it re-enters the tank at least 8 to 8ft from the engine. It would be nice to know if the small bubbles in the return are normal, or if this is a sign of small air leak somewhere I haven't found ? I am in Indonesia where they use BIO/Sulphur based fuels, although I have used these before without a problems
The tank is about 10” (250mm) deep and is just over half full. The return comes out right above the pickup, so probably they are 5” apart.

The engine never had a lift pump, I have added one in trying to solve this problem, but it means that inside the injector pump there must be a conventional/high pressure pump inside the injector assembly. However I would expect any failure in here would not constantly surface after 3-4 hours.

 

[Screen Saver]

Seems air in the return line is normal, back to injector pump.
ie: I just found this quote on a yanmar engine faq "the fuel aerates under high pressure at the injectors and this aeration cannot escape unless it is dumped into the top of the fuel tank", via the return... Perhaps it is normal?

 

[splax]

I made a fuel polishing system by connecting a furnace filter to the fuel line, and then to an electric fuel pump before going to the return line.

 

[SycloneDriver]

I think some air in the return may be normal. I remember seeing air in the lines of an old VW diesel. I don't remember how much air, it's been a long time since I had that car.

Some injector pumps have a low pressure pump inside them and do not have a traditional lift pump. Example late 1970s to early 2000s VW diesels.

I wonder if there is a screen on the fuel pickup tube. I had a car with rust in the tank and it ran fine until the filter screen clogged up. If you parked it for a few minuets you could drive it again for a short time. If you left it parked for hours it would run fine for a long time. It also got progressively worse with less fuel in the tank.

I know some fuel pumps and maybe injector pumps have a very fine screen inside them. Seems unlikely that this is your issue but...

 

[Screen Saver]

The injector pump is a Boch VE injector pump and your right it has a low pressure pump inside it, hence no lift pump and sucks fuel directly from the tank. I found quite good youtube clip on them

Now looking for parts breakdown to check for any filters/screens internally. It would seem the governor could well create this problem as well. The Yanmar manual also says. "For supply restriction excluding fuel filter loss pressure - 1000mm Aq(40in Aq)" Im not sure I understand this. If it sucking, then its a negative vacum, how one measure that is another question. It would seem this equates to about 1.422 PSIV.... (or negative PSI in lay terms) now getting out of my depth

 

[SycloneDriver]

I think I would try bypassing all the current filters, engine mounted filter included, and use a separate high quality filter. Use new line and new clamps. You may have a small air leak in a filter assembly or the primer pump. You could have a hose that has failed internally, happened to me once on a lawn mower and was difficult to diagnose.

 

[jssailem]

Reading the thread, I feel your investigation of the high pressure pump details, while interesting, is leading you down a rabbit hole. These systems need not be seen as complex. I see them as more simple then is being considered.

Air in the return fuel line.
Most likely. You have compressed the fuel to 2000 or so psi (purpose of the High Pressure Pump). When passes through the injectors it becomes an aerosol as sprayed into the cylinders, which is again compressed, and explodes. Excess fuel flows out the return line back to the fuel tank. Where is cools and gives up the air (foam dissipates)

See this list of engine parts. It shows 2 "fuel" pumps. And a single on engine fuel filter.

There should be no internal filters in your high pressure fuel pump.

Do they foul up. Most definitely it is possible. Bad fuel can do it. I under stand it is sensitive and easy to mess up the timing. Why it is generally recommended an experienced tech do the service work on the high pressure pump.

Here is the link to your engine manual. https://www.yanmar.com/marine/wp-content/uploads/2020/05/0AJHM-EN0025_2019.12.pdf

Most boats, I have seen, have an additional electric pump to move fuel from the tank to the engine when the tank is located below and distant from the engine.

 

[SycloneDriver]

I could be wrong but I think the priming is just that, a hand pump only. The lift pump is internal to the injector pump.

There is something small, maybe 2, causing all this.

 

[Screen Saver]

THOUGHT IT WAS FIXED.
Most people told me basically 9 out of 10 fuel related or starvation problems were air leaks, assuming the filters had been replaced. I felt I had exhausted this possibility, but the next step was the internal pump within the injector pump assembly. In my case there is a suction pump inside the main injector pump, that drags fuel from the tank, that option sounded expensive.

In desperation I decided to start again from the pickup hose inside the tank and work my way through every connection, hose, nipple, elbow, O-ring, and seal.. Again in my case 99% of hose clips are doubled, for any underwater, fuel or gas fitting.

When I finally got to the Yanmar filter on the actual engine, on the base of the filter is a water in fuel sensor. Given I was now checking every option I pulled this out and examined the o-ring and surfaces closely. Unlike most O-rings I have seen before, this one sits in a deep “U” shape of the plastic fitting, so if the o-ring was even a little low in its profile it could easily bind or try to seal on the “U” and not the o-ring . In order to seal it needs to stick above the “U” shape to seal on the surface. While it was sticking up just above the “U” shape by maybe less than 1mm, it was also no longer round but had two flat spots where the sealing surfaces meet. Of course I never had a new one , so I cut a larger one and superglued it, to form the right size and shape.

So figuring I found something, time for one more test run. Typically it has not gone for more that 3-4 hours before. So the first 2 hours at 5 knots, next hour at 6 knots, next at 6.5, then hour 5 at 7knots and the last 1/2hour at 8.5 and no signs of problems.

In summary I was convinced this all started with bad/dirty fuel. Another vessel who also filed up where I did dumped 500L because of the same problems. So when I initially changed the filter at the tank, this didn’t fix it because the fuel itself was dirty. Then I changed the filter at the engine , which has the water in fuel sender. That didnt help because the fuel was contaminated. But me disturbing the water in fuel sender when I changed the engine filter I believe disturbed the sealing of the O-ring which was hard and flattened. From there on after I cleaned the fuel and put it all back replacing the filters etc, the problem showed up between hour 3 & 4, probably due to engine heat and different expansion rates, so it mad some sense to me.

Having motored all day yesterday and again today as I go down the East side of Indonesia and head to the East side Papua New Guinea I’ was convinced its fixed..
However day 3, after a couple of days amounting 31 hrs of motoring, bugger me if it didn’t die again. This time rather sharply it didn’t stager as it had done, and did a lot more hours. Of course it stopped at the wrong time when a squall was approaching and I had just reefed for what turned out to be 40 knots on the nose, When I looked at the primer pump which is what I was typically pushing down/pumping to bring it back to life, it was already all the way down, as if someone or something was holding it there. In desperation inserted my Yanmar lift pump in place of the yanmar primer pump/filter, which then completely eliminated the yanmar primer pump and filter. It wasn’t ideal, and I was loathed to remove the Yanmar filter form the circuit and thus relying on the Racor 30 micron filter for any filtering from the tank. Since doing that it has now run 20 hours at quite high load, (2100 rpm) and not missed a beat.
Having now removed the manual primer pump, the only thing I can see that will hold down the plunger is any blockage or restriction on the inlet side of that pump. Ie if I push it down, and hold my finger over the inlet site it will stay down and as soon as I lift my finger of the in the inlet side, it pops up, as it should. So my current deduction is something is blocking the inlet side from time to time. The unit cant be disassembled and it must have some sort of one way valve inside where I assume it blocks So I have cleaned washed blown through as much as I can and we will see what happens next.


Thankyou to all whom contributed, once I get 50 odd engine hours up I will make another update.

 

[Screen Saver]

I have now clocked up 100 Engine hours without a problem... If the above primer filter/pump is not in circuit. So I'm now 100% sure what ever is the problem is, its in the sealed non serviceable unit.
Thanks again for everyone's contribution.