Fuel Lift Pump Failure 2002 M35B

[Dave DeAre]

During our 34 mile trip from Winter storage the M35B on our 2002 34 ran strong at 2600 rpm for several hours, then slowed down to 2000 several times. Made the trip at 2000 rpm with no problems. Changed both fuel filters and inspected the tank all were very clean and the engine then started and ran fine at the dock.
This same sequence occurred on a long motoring trip in 2008 and after filter changes all was apparently well.
About to leave for the Weds Beer Can Race and the engine died and would not restart. The M35B engine  has a fuel bleed screw on the injector pump and the lift pump is initially activated by the glow plug solenoid. Removal of the bleed screw showed no fuel under pressure at the injector pump.

I ordered a new fuel lift pump from Torresen Marine. Their website has on line catalogs for Universal Diesel engines and ships super quick. Replacement of the fuel lift pump resolved the problem and all is now well.

However, I learned from this experience that the lift pump on my M35B did not fail catastrophically, but apparently deteriorated over a period of time. Anyway, if your M35B engine slows down under load, check the fuel lift pump. Contrary to prior posts, at least for my boat, there is no fuel at the injector pump without an operating fuel lift pump. Tank was full.

[Jim Hardesty]

Dave,
I've had engine slow down problems twice myself.  Both times cured by changing the secondary filter (the one on the engine).  All the filters and the fuel appeared clean and had just a little use.  The primary is 2 microns which should plug before the secondary.  I was directed away from a problem with the fuel pump by others saying it's not needed.  To set my mind at ease I may buy a pump for a spare and change when the problem occurs again.
Please keep us posted.  I'm curious.
Jim

[Stu Jackson]

Dave, glad you resolved your issue.

Here's some reading on the subject

Napa fuel lift pumps:  http://c34.org/bbs/index.php/topic,2515.0.html

San Francisco source for Facet pumps:  included on page 2 of that link

A search on the word Napa under my name finds a lot more discussions.  Use the "Search" tab at the top of the MB rather than the search box.

There's also the Critical Upgrades discussion about thew routing of the hoses from the tank to the engine.

A very long discussion about the M35 engine starting and fuel pump circuits is in this topic, down on the third page or so, but still one of my favorite discussions ever! 

Hard Starting & Glow Plug...http://c34.org/bbs/index.php/topic,3347.0.html

[Ron Hill]

Dave : You can also "hot wire" the lift pump to a + source to check out if it's really working. 
Just make sure your oil level is OK because the oil pressire switch may not work properly with the fuel pump lead disconnected. 

[Dave DeAre]

We made an 80 mile 3 day trip this past weekend. Very light wind on the nose both ways and had to motor at least 10 hours. Engine ran perfectly. My problem was definitely the failure of the fuel lift pump.

[Ron Hill]

Dave and MKII guys : I may be opening "Pandora's Box", but the M25/XP engines will run with out a fuel pump in a C34 (all C34s) because the fuel tank is higher than the engine and fuel will gravity feed to the injection pump.
I can not think of a difference in the M35 engines' fuel system that would inhibit gravity feed to that injection pump.  Especially if the tank is over 1/2 full.   
A thought

[Ed Shankle]

Have to disagree with you there Ron. There's at least one m25xp that won't run without the pump - mine! The pump ground wire worked loose last year and the pump, as well as the engine, stopped. Once I figured out it was the ground and snugged it down again, everything worked fine.
Do you supose that having the bleeding screw by the fuel pump opened a 1/4 turn, as has been advocated, has an anti-siphoning effect? Suppose I should experiment with that...

Ed

[Mike and Joanne Stimmler]

Ed, did the engine quit while it was running or were you trying to start it after being shut off for awhile and is it possible that the tank was less than half full?
"USUALLY" once the siphon is started it will continue to flow unless air gets into the line and I don't think the bleed valve would introduce air into the line unless the engine was shut off.

Mike

[Ron Hill]

Ed : I ran my M25XP for a couple of years with the + fuel pump wired from the ignition switch to the blower switch. 
I did that to check the Racor filter status. If I would turn on the "blower" actvitating the lift pump and the RPM went up more than 200 rpm, I knew the filter needed to be changed!

In those days I did keep the bleed valve closed.  Regardless, the lift pump is there (supplied by the engine manufacturer) because the majority of boats have the fuel tank lower than the engine. 

[Stu Jackson]

Have to disagree with you there Ron. There's at least one m25xp that won't run without the pump - mine! The pump ground wire worked loose last year and the pump, as well as the engine, stopped. Once I figured out it was the ground and snugged it down again, everything worked fine.
Do you supose that having the bleeding screw by the fuel pump opened a 1/4 turn, as has been advocated, has an anti-siphoning effect? Suppose I should experiment with that...

Ed, darn, you keep comin' up with new things!   

I found a loose ground wire on hull #90 a few years ago.  The ground wire served the fuel tank sender and had been spliced into the ground for the fuel pump, hidden way, way, way back underneath the head sink towards the forward end of the fuel tank.

Takes all kinds...

From a purely engineering perspective, no supposition is required.  Think about it:  the electric fuel pump pushes fuel to the engine from the tank, the injector high pressure pump is either right before or right after (I forget which and don't wish to "look it up", lazy me!) the knurled knob which only serves, as I understand it, to return fuel to the tank past the injector's demand when the engine is running.

As has been suggested about siphoning, the height of the fuel tank ABOVE the engine allows the injector pump to "suck" enough fuel to keep running because the atmospheric pressure above the "open" fuel tank pushed "down" enough to force the fuel to get to the engine (granted, a very simplistic explanation).

My conclusion is that one has nothing to do with the other.

Now, if ya really wanna get into specifics, try this "Hard Starting & Glow Plug" topic, page 2 or 3 where it really gets interesting with the newer M30 & M35 engine wiring changes that Universal unnecessarily (I believe) made, to complicate matters by having the fuel pump only work when the glow plugs were on or when the oil pressure switch closed.  Nuts, I ocntinue to say...

Reply #52:  http://c34.org/bbs/index.php/topic,3347.45.html

Good luck...

[Ed Shankle]

Mike,
The engine was running and just stopped, after slowing down and sputtering a bit. Close to full tank of fuel.
Ron and Stu,
Maybe something else at play, I just don't know what. All I can do describe the circumstances.... and continue to learn from you guys.

Ed

[Stu Jackson]

Ed,

Sputtering engine means either no fuel or no air.  Rarely no air, so you need to check your fuel system.  Ken Heyman once installed a brand new Racor filter and nothing worked.  Turned ut there was a tiny nick in the Racor that let air into the system.

If it was my boat I'd go through a step-by-step fuel system check for each section of the fuel line.  I'm guessing you have taken the fuel pickup screen out of the hose in the tank, right?

[Ron Hill]

Ed : I've never heard of a C34 engine stopping from air starvation - your problem is fuel starvation!

As Stu mentioned I assume that you've already removed the screen in the pick up tube?!?

Start at the fuel hose that comes into the fuel pump from the tank and make sure that the line is clear.  I'd blow thur it and hear the bubbling in the tank.  Then go to each section of fuel hose and make sure that that section of hose is clear until you reach the injection pump. 

Be sure to look for a bend that's too tight.

I'd suspect that it's a clog as the engine has been running, unless you have recently done some work on the fuel system?  Clogged Racor or engine filter??

Good Hunting! 

[Ken Juul]

Ed,
I'm guessing you have an air leak between the lift pump and the injection pump.  When the lift pump is pumping there is plenty of head pressure so every thing works.  With just the injection pump trying to suck fuel, the leak shows up.  May be so small that you won't notice any leaking fuel.

Check the condition of all the hoses, are they still pliable?  Are they cracked? Replace any that might be suspect. Tighten all the clamps.  Ensure the secondary filter is on tight and the bleed screw snugged down.  Lastly, and the probably cause, ensure all the plugs/fittings/filter on the racor are tight, especially the cap over the manual priming pump.  The various clamps/fittings may only snug down a RCH, but combined or singulary can be enough to cause a problem.

[Ralph Masters]

Ken,
Your navy training is showing with that "RCH" in there.

Ralph