Yanmar Question

[sailaway78]

I'm still having a problem with my 3GM yanmar getting air into the fuel system, after it sits for three weeks or so. Will not start after this amount of time without bleeding the fuel system. I posted up on this pretty good while back, and got lots of answers/suggestions. What I have done so far is replace all the fuel line from the tank forward. Put a "t" in the system with shut offs on both sides to isolate the electric fuel pump. Checked/replaced all the gaskets on the fuel filters. Replaced all banjo washers. Gone over every fitting and hose clamp making sure all is tight. And of course visually inspected every inch of the system for any sign of fuel leakage anywhere. I can turn on the electric fuel pump, put 4 lbs of pressure on the system, and it will hold pressure indefinately. My question for you Yanmar guys. Is it possible for the lift pump to have a bad check valve or a pin hole in the diapharm, that will allow air in, but not allow fuel pressure to leak off. The air is definately getting into the system before the high pressure pump. I can bleed it there, get air bubbles, and the engine will start and run fine, so it is NOT in the high pressure pump, or that side of the system. Only thing left that I can think of is something in the lift pump, but the fact that it will hold pressure doesn't fit with that either.

 

[jimbooth]

Ok, so you are bleeding the air out at the inlet to the hi pressure pump? I think it is possible for the pump to suck air and not leak, however usually that leads to no fuel pressure. I think you could put an automotive generic low pressure pump in place of your existing lift pump. Then see if the problem is still there.

 

[Roger Long]

Your engine has the injector fuel return to the engine mounted filter instead of the fuel tank like the earlier Yanmar's, right? I'm wracking my brain to remember the details but someone went through a long diagnosis of a similar problem and uncovered a generic problem. You could search back through rec.boats.cruising but it probably would be quicker to go to Yanmar. They may recognize this problem immediately.

 

[sailaway78]

Fuel Return

My engine has the return line going back to the tank. Before this problem started the return line went into the fuel line at the tank before this problem started. When trying to figure out the problem, I replaced the return line also, and rerouted it so it goes directly back to the tank. Since I have an electric pump in place, that I normally only use for bleeding when needed, the next step is to by pass the Yanmar lift pump, at least temporarily, and see if that solves the problem. The biggest problem now is the boat will probably not sit that long untill winter. So, I guess it is a moot point till next winter, when it will sit at times for three weeks or more.

 

[Cpt. Jon]

I don't know if this will help or not, but I can only share an experience that I had.

I would have problems once in a while where I would get air into my fuel system, I would have to bleed it on the bleed screw on top of the fuel filter/strainer. After a while it would have the same problem and I would have to do it again. Of course since most of my engine use is coming into our channel between the riprap and sandbar it seemed that of course that's when the engine would quit. After going through this for over a season, and using my boat substantially less last season because of this, I replaced the fuel filter/strainer unit (torreson marine had the part cheap). Turns out that the fuel filter/strainer unit was a little bit stripped from having to bleed the lines there. It's aluminum and the bleed screw is stainless steel or something stronger than aluminum so the filter was giving a little everytime. After replacing that unit and bleeding the whole system once more, I have not had a problem since.

Last weekend we went out for an overnight on the boat... we motored the whole way there and back due to time constraints and comfort and stress for my 7 month pregnant wife. It was great to go out and not have a problem where I had to run up front to drop anchor, troubleshoot/bleed the engine and pray the rest of the way in. The part wasn't pricey and I learned a lot from the whole thing the hard way.

Just one thought though, the screw would seem to seat well even though the housing was a little stripped and it would basically rattle itself loose on the 1GM10, I have no experience with the 3GM, but since they are similar, you may consider this if you haven't.

 

[Dan Johnson]

Easy...

did you replace the copper washers under the bleed screws as well as the banjoe washers? There is (at least on my 3GM and by the shop manual) a nylon type washer under the screw closed to the engine on the filter top. I had a similar problem and found that washer had a crack in it, replaced it, and the problem went away.

If only it were that simple...

 

[Benny]

You lost me with the mention of an electric fuel pump. Does it serve as a fuel transfer pump from the tank? Does it substitute the mechanical transfer/lift pump? I concur that your problem may lie with the pump. It does not make sense that the diaphragm would leak without spilling fuel but when dealing in minute amounts over a three week period pehaps it is not noticeable. You indicate that once the system is pressurized it will remain indefinitely but it seems to me that if that was the case the engine would start even if it died soon after. If it does not start at all after three weeks It is my guess you lost pressure during that time span. If it was me I would go ahead and replace the diaphragm on the lift pump. You may not know how long it has been in service and it would be one less item to worry about in the future. Electric pumps may add more complications not found in mechanical ones.

 

[NYSail]

Try asking the question on the yanmar group site:

yanmardiesel@yahoogroups.com

Good luck.

 

[kloudie1]

Yeoow, Easy.. that is unusual. Do ya have to bleed the filter and the HP pump inlet , or the HP pump outlet at the injectors? I am listing thoughts over a cupof coffee this morning.. One thing to check is the packing of your new shut off valves around the electric bleed pump. A way to check it is to put a drop of oil at the valve shaft/body gap. After you’ve run the engine and everything is bled out. If the oil bead around the shaft disappears over a day or so, you’ve got it. I would suspect something strange like that because the valves are in a different configuration when you are using the electric pump and when you aren’t. (electric pump for bleeding?) There are seals that will seal under pressure and not seal under a slight vacuum. Some other ideas.. the o-ring and seal surfaces on the primary filter.. and a strange one, the bleed screw on the HP pump itself. The manual has an “old” configuration and a “new” one. They may have changed it for sealing issues. Mine is the old with a bleed screw in a banjo at the top of the pump and I have had to dress the gasket under the bleed screw.. If it is leaking air in, when shutdown, the fuel has to be going somewhere.. either back to the tank thru a slightly leaky pump check, or out into the boat somewhere.. But.. you are talking a VERY small leak! It probably takes only a coupla/three cc’s of air to do that and spread out over three weeks, that is almost an evaporation rate for diesel. I am thinking that if most of the air comes out of the pump bleed, the leak is between the filter and the pump .. and if most comes out of the filter, the leak is between the tank and the filter, including the filter..

 

[RichH]

"My question for you Yanmar guys. Is it possible for the lift pump to have a bad check valve or a pin hole in the diapharm, that will allow air in, but not allow fuel pressure to leak off".

Yes indeed you can have both simultaneously ... and that condition will allow air to enter oportunistically ***AT A HIGHER PHYSICAL LEVEL**** than the pin hole. ..... so go back carefully and examine the 'engine guard filter' for leaks from cracked connectors, cracks in the gasket groove, cracks in the bleed screw threads, etc. Do a pressure hold test (vacuum or pressure) on each component bewteen the lift pump and the injection pump. Pressure testing is better since you can apply a soap solution and look for the characteristic 'soap bubbles'.

Hope this helps.

 

[Dan Johnson]

Rich H...

in this case under pressure you would probably see dripping diesel, which is how I found I needed to replace the O-ring gasket on the engine filter canister two seasons ago while repriming the system after I installed a primer bulb between the Racor and the lift pump.

 

[sailaway78]

More info, and an idea

I sorta stated this incorrectly. The engine will always start. With the three weeks of sitting it just won't run long. If I remember to bleed it first, I can bleed at the inlet to the high pressure pump, and all is well. If I forget to bleed first, then it is necessary to also bleed the high pressure side. What I am thinking of doing, rather than pull the lift pump, which will be a genuine PITA, is put a piece of clear tubing between the lift pump and the primary filter. This may give me an idea of whether the air is getting into the system before or after the lift pump. To answer another question. The electric pump was in place when I got the boat. Has a switch on it, and is only used to bleed the system. The two big Fram filters on it are pretty hard to bleed, and no way to change the elements without bleeding. Thus the electric pump. I can stick a piece of clear tubing in between the filters and the liift pump, and if I get bubbles there, can put it before the filters. Should give me some idea of where the air is coming from. Since spring has sprung, not a rush. Doubtful it will sit for three weeks without starting before winter.

 

[Chris Burti]

Re: More info, and an idea

This is not likely to help, but since you've tried everything else and your symptoms are the same as mine, I'll share this in the hopes that it may lead to a solution.

On certain year models of our C-320's with the 3GM, Catalina installed a check valve in the fuel return line. This valve was allowing just enough air to back feed into the system to cause the described symptoms.

There is repair memo on one of the major Yanmar discussion sites and it is copied on the C320 Association website.

Interestingly enough, I discovered a temporary solution while procrastinating on completing a proper fix. Pumping the Racor filter pump 5 or 6 times before starting after a long layover will resolve the problem without bleeding.

 

[Stu Jackson]

Interestingly enough, I discovered a temporary solution while procrastinating on completing a proper fix. Pumping the Racor filter pump 5 or 6 times before starting after a long layover will resolve the problem without bleeding.

Chris, great input, thanks. Wouldn't cycling the electric fuel pump do the same thing? I once tried the pump on the Racor and all I got was a bloody finger!

Do you have a link to the C320 discussion.

 

[Don12480]

Lift pump

I had a problem last year with my feed or lift pump. It always started well and ran fine for a while but later would slow down as it was getting choked for fuel. I took the pump out cleaned and re-assembled and it seems to be fixed. The membrane was intact but the check valve was not functioning.
I have purchased a new pump and will install soon as it was not that expensive.

 

[Stu Jackson]

What I am thinking of doing, ... is put a piece of clear tubing between the lift pump and the primary filter. ... I can stick a piece of clear tubing in between the filters and the liift pump, and if I get bubbles there, can put it before the filters. Should give me some idea of where the air is coming from.

Assume the clear tubing will be only temporary, as it's not rated for diesel fuel. Just be very careful.

 

[Chris Burti]

Chris, great input, thanks. Wouldn't cycling the electric fuel pump do the same thing? I once tried the pump on the Racor and all I got was a bloody finger!

Do you have a link to the C320 discussion.

Sorry it took so long it was buried. It is a scan of a Yanmar service bulletin.

http://www.catalina320.com/filemgmt_data/files/Hard_Start_Yanmar.pdf

I don' t know why the electric bleed pump shouldn't work as, from the description, it seems to perform the same function as the manual pump on the Racor..

 

[sailaway78]

Thanks a bunch

The check valve in the Yanmar bulletin may very well be the answer to my problem. I didn't even know there was a check valve in there, and I don't believe my manual even shows it. Is certainly about the only thing I have not checked or preplaced. I know the air has to be getting in ahead of the high pressure pump, as bleeding it at the inlet to the high pressure pump is all that is needed, if not started first.

 

[Benny]

Hope you have found your solution, but if it is not a check valve, consider simplifying the secondary fuel filter installation. A single Racor turbine series will do the job and will not need an electric fuel pump to bleed it. A 500FG2 sells for about $250 but is worth every penny.

 

[Roger Long]

Wouldn't cycling the electric fuel pump do the same thing? I once tried the pump on the Racor and all I got was a bloody finger!

I wired a simple doorbell button from my bilge pump + connection (before the battery switch and always on) to my electric fuel pump. Pressing it turns on the fuel pump and makes bleeding a snap. It's located in the best position to reach when turning the connections on the fuel lines. I usually push it until the pump stalls out when opening the RW seacock just to be sure the fuel system is fully charged and pressurized.

The button also turns on all the engine alarms when it is pressed but that's not a problem and would alert me if the inexpensive switch were to short or jam closed.