Diesel Engine fuel system

[ken003]

I have the M35B engine in my 2005  C34 MK II.  When starting, the key is turned to the second postion, all the way to the right.  This starts the glow plugs.  While I am holding the key in this position, is the fuel being pumped?  Does it simply go through the return lines back to the tank?  In the first (start) position, is the fuel pumping just the same, only without the glow plugs on?  If I want to bleed the fuel lines, do I simply turn the key to the first position and look for fuel wherever I want it to bleed?

Ken

[Joe Kern]

Ken - My understanding is the only difference with the key in the second position is the glow plugs are going.  You do not need to have the key all the way to start once the glow plugs have been heated up.  Fuel must flow in both positions.

Joe

[Stu Jackson]

1.  Check your manual for the wiring diagram.

2.  Have a crew member check the fuel pump in both the first and second key positions.  If you have the new "electronic" fuel pump you may not obtain any sound, but the OEM metal-housed pumps should click.

3.  Normally the fuel pump IS on when the key is on.  This is helpful for bleeding.  If doing a "singlehanded" bleed, recommend installing Ron Hill's idea of a separate shut off switch on the fuel pump to allow turning the pump off from the engine area so you can get the screw back into the top of the secondary fuel filter housing without having to go back up to the cockpit to turn the pump off.

Also make sure you have the recent notice on the filter bracket in mind.  See: http://c34.org/bbs/index.php?topic=2804.0

[reedbr]

Ken-

As has been answered, the second key position is for the glow plug.  I hold it there for 10-15 seconds when the engine is cold, then release to the first position and hit the start button (then look for water out the exhaust).

Regarding bleeding the fuel system, I just did it again this weekend so it is fresh in my mind.  I've tried several methods on my MkII, with one person and with two, using the fuel pump and not, using a separate can of fresh fuel or not.  On a MkII, if you are only changing the RACOR (mine is a 15S filtering down to 2 microns in theory), one person can do it simply using the fuel line cutoff valve in the port cockpit locker under the forward inspection port.  My process is:
- Shut off the fuel (valve perpendicular)
- Go below and remove the old filter
- Spin on the new filter (with all gaskets ) stopping with a slight gap between the gasket and the upper mounting surface (so air/fuel can escape).
- Go back up top and open the fuel valve.
- Go down below and watch the filter fill with fuel. 
- When it is full it will overflow the top rim of the filter.  Spin it the rest of the way on by hand.
- Cleanup
- Start the engine, run it for 15-30 minutes at part throttle, maybe even in gear for part. 
Done.

Previously unstated is that you catch any spills with the oil-absorb rags. I have had no luck with the bleeder on top of my RACOR assembly.  I have changed my engine mounted filter only once (30 micron filtering after the RACOR doesn't catch much).  In that case, I used the bleeder on top of the engine mounted filter assembly and it worked fine.  If all else fails, the key in the "on" position, engine off will run the fuel pump for any bleeder to receive pressure.  Oil alarm is noisy though.  I've never "heard" my pump run but obviously it does. 

[Stu Jackson]

The link to the fuel pump story is: http://c34.org/bbs/index.php?topic=2515.0

Also, as Brian mentioned, make sure you release the glow plug before you hit start, there's no reason to have both on at the same time.

My Item 3 in my post above was for the M25 and M25XP engines, where the bleed needs to be done at the top of the secondary engine-mounted fuel pump.  My understanding is that the M35 engines are more "self-bleeding."

[Roc]

Hey, this is news to me....I've been starting my engine by turning the key to the second detent, counting to 10 (if engine is cold), then hitting the start button.  I've never turned it back to the first detent when I hit the start button.

[Stu Jackson]

No need to hold the glow plug and the start.  From an earlier thread: http://c34.org/bbs/index.php?topic=1757.0

The glow plugs get hot and will stay hot in the time it takes to release the glow plug button or key position 'till when you hit the start.

[Ron Hill]

Roc : If you release the glow plugs on the key switch you allow more power to be available for the starter.  The glow plugs are a real current drain and the plugs should be hot enough by then anyway.  A thought. 

[Ron Hill]

Brian : There's a much less messy method of changing out your Racor filter than what you're doing:

1. Turn on the key switch and control it's power by the battery selector switch - saves running up and down the stairs!!
2. A simple ball valve screwed into the fuel inlet of the Racor head - saves running up and down the stairs!!
3. After turning off the fuel and removing the old filter. Separate the water separator from the old filter.  (If you hold an old coffee can under the old filter assembly you can screw it off and let it fall into the coffee can - no mess)
4. Wet the gasket of the water separator with some diesel and screw the filter onto the new filter.
5. Fill the assembled pair with fresh diesel fuel to the top.
6. Screw the filled pair onto the Racor head.
7. Open the fuel line.
8. Turn on the battery selector switch so the electric fuel pump comes on and proceed to turn ON & Off the engine bleed valve a dozen or so times (leaving it on 5 or 6 seconds each time).  I'm not sure if you can hear your fuel pump or not, but the little air that was in the line should have passed thru to the fuel return line to the tank.
9. Let the bleed valve ON 1/4 turn and start the engine.
10.Run the engine for about 5 minutes
11.I'd let the bleed valve open that 1/4 turn so you have a "Self Bleeding System)
Then check for seals around the 2 seals of the Racor.

DO NOT CHANGE BOTH FUEL FILTERS (Racor & Engine) in the SAME operation - if you do you'll introduce more air into the system all at once and have a "BEAR" of a time bleeding it out.  One filter at a time running the engine in between!!!!

You're done and it only took 1 paper towel!!   A few thoughts.   

[Jack Hutteball]

Ron,
I regulary change both filters at the same time (although with a 2 micron Racor I am probably wasting money) and fill them both up to the top and screw them back on.  I have never turned the bleed screw.  Everything seems to run OK when I start the engine.  I have been doing this for four seasons now with no problems. Have I just been lucky?

Jack

[reedbr]

Jack-

That's sounding more like my experiences with my '97 MkII/M35B.  Not specifically changing both filters since i've only done that once in 4 seasons, but with the lack of troubles in general.  I have heard many warnings and horror stories, but my filter changes have been painless.  So painless that the first time I ran the engine for an hour for some sign the fuel line seal had been broken.  Nothing, not even a hiccup.  Maybe the design changed.  I'm certainly not complaining.

Thanks for your feedback Jack.  It makes me feel more "normal"!

[Ron Hill]

Jack & Brian : Let me clarify my statement: 
IF you do multiple things to your engine at the same time and all are done PERFECTLY there's no problem.  People screw up and if you run the engine after EACH item, when the engine WON'T run you only have ONE item to check.  This is especially true if you happen to encounter multiple problems at the same time!!

Guess that other people are more meticulous and smarter than I.  Think you've been lucky so far, but will still recommend that you do only one item at a time.  Then you'll still be a happy C34 owner -- 18 years later.  A thought.   

[Jack Hutteball]

Ron,
Thanks for the insight.  I never have bled the system after changing the filters. Should I be actually doing this after each filter change?  My previous Petter diesel was self bleeding and I have assumed that all newer engines would be also.  I like to keep things as simples as possible and do things right so that I don't encounter problems in the future.
Jack

[Ron Hill]

Jack : I know that if the bleed valve closes all the way the M25 series and the M35A engines are not self bleeding.  I'm not to sure if the M35B has a built in self bleed or not. 
There is a simple way to check - There's a fuel return line off the furthest aft injector.  Remove it from the last injectors banjo.  Take a same size hose and attach it to that banjo outlet and put it into a container.  Then start the engine with the bleed valve closed.  If fuel comes out of that hose attached to the aft banjo -- then you have a self bleeding system.  If fuel comes out only when you have the bleed open then you do not have a self bleeding system.
 
That's why I recommend that everyone let their bleed valve open 1/4 to 1/2 turn so they do have a self bleeding system.       

[David Arnold]

My boat is entering it's 2nd season and I'm about to start the spring commissioning.  With the engine having only about 75 hours on it is it necessary to change either or both of the fuel filters?  In the fall I changed the oil and filter, transmission fluid and the zinc in the heat exchanger.  What if anything needs to be done to the engine at this point aside from checking the impeller?