Air in Fuel System -- Yanmar

[sartorst]

Also note that the people who say there engine starts right up with no bleeding most likely have electric fuel pumps as opposed to manual engine driven pumps and those who have electric fuel pumps prior to manual pumps have a catastrophe waiting to happen as in-- when the diaphragm in the manual pump starts to leak into the crank case and dilute the oil and cause bearing problems OR worse oil level raises to a point that it begins to hit the crankshaft and the fuel/oil mix is ingested a run away occurs its a helpless feeling !!
"My Last boat was set up that way and it has worked for years on this boat " The sick owner says

[kmcshane]

My engine started stalling mid-run.
The Yanmar repairman, Bo, here in St Augustine suggested I get rid of my electric fuel pump to my 3GM30F. Reason: (I'm paraphrasing: 'If your primary fuel pump diaphragm tears (leaks), the electric pump will continue to pump fuel past the pump leading to overfilling the combustion chambers (cylinders).'
You all may differ or offer alternatives.
He also said the electric pump can get clogged up or gritty with contaminated fuel, since it's before the Racor.
I replaced the electric with a squeeze bulb. Also, I have a small diesel canister for quick Racor refills.
My engine kept stalling. Fuel tanks pristine, fresh fuel, new Racor, but it came equipped with a 2 micron filter. The suction gauge was pegging, and then stall. At Bo's suggestion, changed it to a 30 micron primary Racor filter. Problem solved

[Cheechako]

Originally Posted by kmcshane

My engine started stalling mid-run.
The Yanmar repairman, Bo, here in St Augustine suggested I get rid of my electric fuel pump to my 3GM30F. Reason: (I'm paraphrasing: 'If your primary fuel pump diaphragm tears (leaks), the electric pump will continue to pump fuel past the pump leading to overfilling the combustion chambers (cylinders).'
You all may differ or offer alternatives.
He also said the electric pump can get clogged up or gritty with contaminated fuel, since it's before the Racor.
I replaced the electric with a squeeze bulb. Also, I have a small diesel canister for quick Racor refills.
My engine kept stalling. Fuel tanks pristine, fresh fuel, new Racor, but it came equipped with a 2 micron filter. The suction gauge was pegging, and then stall. At Bo's suggestion, changed it to a 30 micron primary Racor filter. Problem solved

Yes, that's a downside if you leave your mech pump in the system for sure. .... except I think he meant it may fill the oil sump with fuel...? I doubt it will go thru the injection pump and injectors...?

[Dockhead]

Originally Posted by Cheechako

Yes, that's a downside if you leave your mech pump in the system for sure. .... except I think he meant it may fill the oil sump with fuel...? I doubt it will go thru the injection pump and injectors...?

Not relevant in any case on my boat, as I have not a diaphragm lift pump, but a roller cell fuel pump integral with the injection pump, so it can't put fuel into the sump.

[transmitterdan]

4JH series engine is self bleeding from pressure pump to injector. You should never have to bleed injectors. I have never needed to do it. If engine starts and dies just start again and it will eventually self bleed.

Most likely cause of slow top speed is restriction in fuel flow or problem with lift pump. Next most likely is tiny air leak on suction side of lift pump. Bleeding is not the problem if the engine runs smoothly at idle. If it needs bleeding it won't start.

[David Clark]

Had an air in fuel system last season with our 3GM30F Yanmar Changed filters checked all hose connections at filters and engine.
Finally checked fittings on top of fuel tank and found a crack in fuel pick up elbow on top of the tank,this was sucking air in but no apparent fuel leaking out.
Replaced pick up tube and fitting did a quick bleed no further problems
FYI this was on our 1997 Beneteau 321

[01kiwijohn]

Question; why are you bothering with fuel flow sensors on such a small engine? Top off the tank, run at hull speed for a few hours, top off again and record "fuel used". After that, record hours, in the log, do a little simple math and bingo, you'll know what you are using and how much is left. Close enough for all the sailboats I've been associated with, and no moving parts.

Use proper MARINE fuel hose (it's much thicker than the usual automotive hose) and the correct sized clamps, to be sure you have NO suction-side leaks.
Racors are great filters but, you do need to replace the O rings and seals (provided in the kit) and top them off with CLEAN fuel.
On this engine model you should not have to bleed the injectors, as I recall, the excess fuel return line should take care of that. It may miss and stutter, initially, but will clear up after a few moments.
You probably can't bleed the injectors, with the stop control activated, because that shuts off fuel delivery from the injector pump thus there should be no fuel delivery to the injectors.

Now, you don't say how many hours on the engine so, assuming the external system integrity is good, the problem could be the in the delivery check valves, in the top of the injector pump; not usually a job for a home-handyman type. This usually shows up at over 3000 hours or so.
Good luck, and let us know if that helps.....or not.

[lordgeoff]

Originally Posted by twinboat

I think your getting close with the low filter level on the Racor. Air would be getting before or on it.

Adding fuel pumps shouldn't be nessessary. It worked since new, so something changed.

Adding pumps just adds things to give you trouble and could mask other problems.

If it ain't broke, don't fix it.

Have you checked the filter at the bottom of the main suction pipe coming from the tank before the Racor filter. You may have an intermittent blockage that is restricting flow. Is your fuel and tank clean? No bits of gunk floating around in your fuel tank? Just an outside chance.

[Stu Jackson]

Originally Posted by sartorst

<SNIP>
My dock neighbor changes his filters and just grinds away on his starter until it starts and when I recommend bleeding he tells me "It's self bleeding " "Well you don,t have to but there are only so many starts in a starter and I will save mine for the day I am close to the rocks" Is my response

That's the advantage of an electric fuel pump. For those engines that are self bleeding, it simply gets the fuel there faster.

[Stu Jackson]

Originally Posted by kmcshane

He also said the electric pump can get clogged up or gritty with contaminated fuel, since it's before the Racor.

Wrong place for it then.

Many electric fuel pumps are called LIFT PUMPS.

Why?

'Cuz the fuel tank is below the engine.

[Dockhead]

I remade the connections, but the problem is still there -- and even worse.

This is pas bon.

Could be a leak in the sensors themselves, or maybe the hose bibs aren't fitting right (I used sealing compound as per the instructions), or maybe the hose bibs, which have very sharp barbs and are the very b**** to get the hoses on, are wrong. Or maybe the hoses developed a crack or hole with all the handling I gave them.


It's not as easy as I thought to bypass the sensors as I thought since the Racor end has a crimped on compression fitting connector so I can't just slap on a different hose. It looks like I might be able to use a bit of copper tube with an olive as a hose barb.

Tomorrow I want to try to rig up such a bypass, using clear hose so I can see if there are any bubbles.

I guess any 3/8" ID PVC clear hosing will do for this? Any one try it?

[twinboat]

Originally Posted by sartorst

Also note that the people who say there engine starts right up with no bleeding most likely have electric fuel pumps as opposed to manual engine driven pumps and those who have electric fuel pumps prior to manual pumps have a catastrophe waiting to happen as in-- when the diaphragm in the manual pump starts to leak into the crank case and dilute the oil and cause bearing problems OR worse oil level raises to a point that it begins to hit the crankshaft and the fuel/oil mix is ingested a run away occurs its a helpless feeling !!
"My Last boat was set up that way and it has worked for years on this boat " The sick owner says

I have a disaster waiting to happen engine. I remove the old spin on filter, put a spot of oil on the gasket of the new one and screw it on, hand tight.

Next, I stroke the little lever, fitted to the 32 year old engine mounted, camshaft driven, diaphragm pump until I feel some resistance. A few more strokes and I turn the key and the engine starts quickly, as usual.

I have run the engine until it stalled from clogged filters many times and either switched the dual Racor or changed the spin on. A few strokes on the disaster pump and off I go. I don't have air leaks in my fuel lines.

In the 8 years I have owned the 1984 boat, I loosened the fuel injector lines one time. That was to replace one due to failure. Still didn't bleed it to start it.

For 30 years I serviced and repaired diesel powered equipment. In that time I recall bleeding a hand full of engines. That was because I had done major work on them. Of course I always primed the fuel system according to the manufactures recommendations.

And as a said before, I would get enough cylinders firing to keep it running until the rest bleed out by themselves.

There are only so many times you can loosen and tighten injector nuts before they crack and leak.

Your engine may be a rare one that needs bleeding every time you service it but it is not the normal way to start most.

It sounds like you don't or can't prime your system. If that's the case, starting it with empty fuel filters, will cause it to run on the fuel remaining in the high pressure lines until it is gone. Then bleeding may be nessessary.

All diesels are not alike.

Have a good day.

[Dockhead]

Originally Posted by twinboat

. . . It sounds like you don't or can't prime your system. If that's the case, starting it with empty fuel filters, will cause it to run on the fuel remaining in the high pressure lines until it is gone. Then bleeding may be nessessary. . . .

??

I don't understand this. If the system weren't primed, it wouldn't start, would it? Or at least, it wouldn't keep running?

I don't have that problem -- it starts instantly and runs happily and smoothly 1500 RPM or less.



I think what I have is either a tiny air leak at the new fuel flow sensors, or which I created in one of the hoses with all the handling of them I did, or else the slight resistance from the sensor on the supply line is exacerbating a tiny leak I have always had.

I'm going to go through the diagnostic list today, but if it doesn't work, I'm just going to install a new fuel hose and forget about the sensors for now. I'm running out of time to get through the rest of my list. It's staggering how much time I've lost on this.

One problem I have is the crimped on compression fitting on the Racor which I doubt if I will find here in Cowes. I'm sure hoping that I can just use a bit of copper pipe with an olive.

[transmitterdan]

Dockhead,

You may be able to find the location of the problem by creating a small "day tank" using a plastic jug with a hose fitted. Put a couple liters fuel in the jug and connect the hose directly to the engine fuel input connector thus bypassing all the boat side fuel system. If the engine runs normally the problem is not the engine. If it still runs bad the problem is with the spin on filter or lift pump (least likely is the injection pump).

If it runs normally back up one joint at a time through the fuel system until you can duplicate the problem. Then you have found the source of problem.

[Dockhead]

Originally Posted by transmitterdan

Dockhead,

You may be able to find the location of the problem by creating a small "day tank" using a plastic jug with a hose fitted. Put a couple liters fuel in the jug and connect the hose directly to the engine fuel input connector thus bypassing all the boat side fuel system. If the engine runs normally the problem is not the engine. If it still runs bad the problem is with the spin on filter or lift pump (least likely is the injection pump).

If it runs normally back up one joint at a time through the fuel system until you can duplicate the problem. Then you have found the source of problem.

Thanks -- yes, that's in my plan.