Question about M35BC lift pump

[Breakin Away]

I'm trying to diagnose an issue with plugged fuel filter and/or air leak into my fuel system. I know that the lift pump operates when the key is turned to glow plug position. Once the motor starts, does the lift pump continue to operate, or does suction from the high pressure injector pumps pull the fuel in without a lift pump? (Neither owners manual nor service manual is 100% clear on this, though there's a slight hint in the troubleshooting that the former is the case.) If it's actually the latter, does anyone know for sure whether the secondary pump is under negative pressure or positive pressure?

In a related question/comment, if the lift pump continues to operate when the motor is running, I assume that the excess fuel continuously recirculates back to the fuel tank, continuously polishing the fuel. Is that correct based on your understanding? (Note that this is an M35BC model.)

[Stu Jackson]

Check the Critical Upgrades, there is discussion about just this operation.  Top of page 3.

[KWKloeber]

The B series wiring is a strange duck.  Back-asswards (unless like Ron you rewired it.)

The lift pump is powered through the low oil pressure switch.  Oil pressure, the pump is powered.  No pressure, no power to the pump.  So as long as you have a 1) good switch, 2) the stiff SAE, not non-marine Type 3 wire, harness hasn't broken off one or both terminal tabs) and 3) there's oil pressure -- you **should** have power to the pump.

Since there's no oil pressure before starting the engine, the pump is powered through a back-fed circuit (via the preheat solenoid mounted on the engine.)   

Further, the fuel pump and oil switch circuit is powered thru the same circuit as the alternator field excite.  In other words, on M-25/XPs there are two circuits fed from the key switch -- fuel pump and alternator excite (so redundant).  On the B series, these are combined into one circuit fed from the key switch.

Schematics for the B-series are on the Tech Wiki.

Yes, diesels have a return fuel line -- excess fuel that the injectors "don't need," is picked up by the banjos and returned to the tank.  The amt is controlled by the relatively small amt of fuel that bypass the injectors and the small lines from the banjos on each injector.

ADDITIONALLY, the XP and some M-25s have a bleed knob and a bleed hose circuit, opening which bypasses the injector pump, and MORE fuel is returned to the tank.

The B series has a bleed SCREW (similar to the original M-25s) where you bleed fuel/air into a cup, no lines to return it to the tank.

Although fuel is returned on the B series, it's not enough to call it "polishing".  It's a stretch to call it polishing on the XP.

kk

[KWKloeber]

PS the Catalina Schematics are in the Operators' Manuals.

k

[Breakin Away]

I have the filters replaced, and after a few small issues with air, everything now seems to be successfully bled and running well.

I'd like to install a vacuum gauge to proactively monitor filter performance. In addition to avoiding failure when "out there", I want to minimize replacement of these very expensive spin-on filters. My boat has the Racor 215 separator, which apparently was selected for the C34MkII because of the limited vertical space under the aft berth. It's an OK separator, but the spin-on filters cost $43 each, which really gives an incentive for a vacuum gauge to minimize frequency of replacement.

Because of the limited vertical space, I can't just stick a gauge on the bleed port on top. (I also can't upgrade to 500 series in this location because of the space limitations.) I either need to attach an elbow to the top to make the gauge horizontal, or install a T somewhere on the fuel hose between the primary filter and the lift pump. What do you guys suggest?

I've searched the site for info on this, but can only find info on the older boats with larger filter located in the head cabinet. If there are links to other things that I missed, I'm happy to look at them. But please make sure they're relevant to the MkII configuration that I have.

[Breakin Away]

I had a few more air problems yesterday, as described in this thread. Things are working OK for now, but it did raise some questions about rubbery debris in my filter bowl, as well as other questions:

http://www.sailnet.com/forums/general-discussion-sailing-related/290970-rubbery-debris-racor-filter-lift-pump-fragments.html#post3996298

As you can see in that thread, I am also beginning to have some questions about my lift pump.

One additional question that some of you might be able to answer: My lift pump always clicks rapidly. It never slows down, no matter how long I run it. (I never run it more than 20 seconds without a cool-down period before running it again.) Is this lack of slow-down because the B-series motors have a recirc loop that allow free flow of fuel back to the tank? (In other words, the pump never dead-heads like it might on the earlier models without the recirc loop)? Or is the fact that it never slows down a sign that the pump is not pumping properly (perhaps due to degradation of the diaphragm or check valves)?

FYI, this pump appears to be the original one, with the square housing.

[KWKloeber]

BA

What do you mean by "return loop."? All diesels have a return loop, but it's only the tiny amount of fuel picked up by the injector banjo.

To my knowledge none of the B series have a bleed bypass like on the very late M-25 and the XP.   In fact the B series have the exact same bleed type as most M-25's, which is simply a bleed screw where you catch fuel in a cup   

Note that a customer needed to replace his fuel pump on a not so old B series.   Replacement cube pumps are called out in the tech wiki.  I'm not suggesting is necessarily the correct route, but he replaced his "temporarily" with a $20 cube pump from NAPA.  I'm sure he won't put on the facet pump and left the other fails  or he sells the boat   

The facet pumps are basically a piston and ball valve arrangement not a diaphragm pump.

kk

[Breakin Away]

My source may have been wrong, but my diesel instructor told me the main difference of the B series is self-priming bypass loop, which older models lacked. I trained on a real old Universal that lasked the feature. I don't think it was a M25.

Mine also has the bleed screw, but IIRC the manual implies that you shouldn't need it because system is self-priming. I used this screw to confirm no-flow condition when I had an air problem.

If he's wrong and they are all the same regarding bypass, then I need to figure out why my pump doesn't slow down as described by others.

Are there any M35B owners here who can confirm their pump slows down once pressured up?

[KWKloeber]

 There may be a permanent "loop", but I just haven't eyes-on one. And you can't really tell from the parts book.
I do know the  owners manual does claim the B series is self bleeding, without any explanation how/why.

If he's been hands on the B series, then he's probably knows more about it.

[Breakin Away]

Maybe my terminology is misleading. The only loop that I see on my motor is the one that goes:

Tank → Racor primary filter → lift pump → Engine secondary filter → banjo washers → return to tank

This provides a self-priming source of fuel to the banjo washers, available as needed for pumping into the injectors. That is the only recirculation loop that I am aware of on my B-series motor.

Is this what the older motors have? I thought that the older motors (like the one in my diesel class) had  dead-end on the last banjo washer. In this case, the lift pump would slow down dramatically once the system pressured up, because it would be dead-heading. In my case, I was thinking that my lift pump doesn't slow down because it never dead-heads; it just continuously recirculates any excess fuel back to the tank. Another MkII owner can blow away this hypothesis by confirming whether their pump slows down after running a few seconds.

But now I wonder if my pump runs fast because it's not pumping properly. I haven't studied how the pump works. If it's a piston like you say, then there must be internal check valves to ensure the piston is pumping in the right direction. So maybe the check valve (ball or flapper?) is degraded and the piston clicks away without pumping anything.

I am aware of more recent design changes in lift pumps which chatter at high frequency, presumably due to a piezoelectric mechanism. So it may be time to research those options and get a spare and/or replacement pump.

In the meantime, I guess the easiest way to test whether my pump is working is to attach some hose that's long enough to lead up above tank level and see if the pump can lift the fuel above that level. Since my fuel tank is full, I'm not going to be able to have any sort of real test of the lift pump with the tank providing a pressure head that overcomes the pump's malfunction.

EDIT: Another question - I see some references to a coarse filter that's built into certain lift pumps. Does my square one have such a filter? Are there instructions anywhere for how I can open it up and check this out?

[KWKloeber]

Ok I looked at the parts service and ops manuals.  It appears there is a bypass on the B series that's not on the M25.  And I've seen it called "self bleeding"   But the Westerbeke manuals don't explain how it works or the hose purpose.  Typical effin Wb not providing clear and complete information to owners. 

And although they call it self bleeding, Wb gives a bleeding procedure.  D'oh.  And it doesn't mention the bleed screw on the injector pump (identical bleed spot as on the early M25s and the same spot as the XP bleed procedure.)  Instead, tells you to bleed at each injector.   Again typical effin Wb not producing clear and concise manuals.  After dealing with defective parts shipped out of the warehouse, i.e., 4 bad exh flanges and 3 bad risers, I expect no less out of them!

kk

[Ron Hill]

Breaking : There is a course fuel filter just before your M35"B" fuel pump. Found on both the M25XPB and M35BC engines.

Originally there was a sticker on the starboard side of the engine warning of the filter.

A thought

[KWKloeber]

Breaking : There is a course fuel filter just before your M35"B" fuel pump. Found on both the M25XPB and M35BC engines.

Originally there was a sticker on the starboard side of the engine warning of the filter.

A thought

Ron,

Is this additional filter not shown on the parts manual?

ken

Also, I can say it was NOT on all XPBs, e..g., the customer who replaced his fuel pump did not have a second on-engine filter.

[KWKloeber]

BA

You're missing a lot of parts there.  The fuel feed doesn't go to the banjos, it goes to the injector pump.

I think I posted something like below on here before -- maybe it was for the XP. 
The below for the XPB, add another cyl for the 35B.
The schematic is similar for the XP, except subtract the "hollow bleed screw," and there's an adjustable bleed valve (knurled knob) on the "bleed bypass."

FUEL
FEED
  |
  |
  V
___                  / cylinder #3             
I    |=> inj #3 |
N   |                \ _________banjo #3 ----> fuel return hose -----> tank
J    |                                      |
E   |                 / cylinder #2   |
C   |=> inj #2 |                      |
T   |                \__________banjo #2
O   |                                      |
R   |                       / cyl #1    |
     |==injector #1 |                |
P   |                       \______banjo #1
U   |                                       |
M   |== bleed bypass hose===|
P   |
__ |-hollow bleed screw--->

[Breakin Away]

Thanks for the info. I have some more studying to do, because I didn't think that the banjos were downstream of the injector pump. I thought the banjos provided the fuel reservoir for the low pressure side of the injector pump, and once the fuel entered the pump it was off the recirc loop and headed into the cylinder. That's why I left it off my depiction of the recirc loop. I didn't flunk my diesel course, I just forgot a lot of stuff since I took the course (like where the injector pump is located).

Next time I'm at the boat I'll have to re-trace the lines, though I'm sure you're right since I think there are metal tubes (high pressure) leading into those sections. I wasn't thinking things through.

I'll also have to go re-count my cylinders, because I could have sworn I had four. I think I'm right about that one.