Fuel system

[Ken Juul]

Spent the weekend visiting sunny south Fla.    Boat shows, airboating in the Everglades, walking the boardwalks with the rest of the spring break crowd.       Now as I sit at work with the weather reporting a chance of snow showers I ponder the lack of power issues I brought up a few weeks ago.  

I remember last spring when I changed my Racor there was a discussion about leaving the bypass valve cracked to create more flow to "polish" the fuel.  I know I left it open, I think about a half a turn.  I have not checked it yet, but is this too much?  If it vibrated open further could this be a cause of power loss?  Really hoping it is something simple, before I dive into injectors and possibly the injector pump.  The Racor is replaced annually, the engine filter is replaced every other year.

[Ron Hill]

Ken : The bleed valve can be open a couple of turns and it should NOT diminish engine power.
Change out your injectors ( I assume that you've changed both fuel filters).  There are two Mainsheet articles to guide you thru that process.  Be sure that you get a good seal where the injectors seat in the head - check with soapy water and look for bubbles.
If the power is not restored, then you'd better think about a compression check and after that the injection pump.

Good luck.  

[DEMERY]

Ken,

Wow, let's start with some less expensive approaches first. How about closing the bleeding valve, replacing both your primary and secondary filters. You may want to put fresh fuel in your filters before installation to eliminate a fuel problem. If it runs great for a couple minutes and then begins to loose power, might be your fuel supply. How about the screen on the bottom of the fuel pick up tube. Has that been removed? How about the screen in the fuel pump, have you re-plumbed your fuel system to have the primary filter before the fuel pump? Lots of things to check before we crack open the engine.

Good Luck,

Dave

[Mike Vaccaro]

Ken,

Agree with Dave--start by searching this site and the C36 site and learn about cleaning the fuel system.  In all likelihood, it's the most likely culprit.  Can't really rule out other problems, but it may be difficult to diagnose until you've got a clean fuel supply.  Always endeavor to fix the easiest, cheapest thing first and then work yourself into a pit from there!  

If you've got any sediment at all in your primary filter, you should consider the tank suspect for contamination.  Ron wrote a great article on how to remove and clean the tank, and there are other posts, FAQs and Mainsheet articles on system maintenance.  

If your fuel system is 100% clean, then Ron's trouble-shooting tree is on the mark.  Don't forget to research Kubota parts as an alternative to Universal if you need to buy anything!  Plenty on the site for a "search" or "find" on that topic as well.  

Cheers,

Mike

[Ken Juul]

Thanks for the imputs.  Fuel pickup screen is removed.  Pumped the tank dry last year and got nothing other than fuel out of it.  Power issue is the same with new fuel or old fuel.  It all started when I reproped the boat, so I will verify the pitch is correct and try changing the filters before I start tearing apart the motor.  I just don't want to over look something simple.

[Ron Hill]

Ken : I assumed that you checked all of the simple stuff that's been written up a zillion times.  Try this quick check:

Take the fuel hose off of the injector pump (it's actually easier to take that hose off of the engine filter inlet).  Turn on the key switch (activating the electric fuel pump) and the fuel should squirt out of the end.  Be careful so the fuel doesn't go all over the place.  If your fuel tank is over 1/2 full the fuel will probably siphon out - without the pump on!!  This lets you know that the injection pump is getting plenty of fuel.  
The injection pump takes a minuscule amount of fuel and puts it under tremendous pressure to the injector at just the correct time (TDC of that piston).
So if your engine has fuel to the injection pump, the problem is narrowed down to the pump, clogged injectors, compression or possibly too great a load (over pitched prop/too large a prop).  However, if it's the prop you'll usually see allot of telltale black smoke coming out of the exhaust.  
As I mentioned in last months Mainsheet, the loss of power with out overload symptoms means that there's not enough fuel to the cylinder or that cylinder has poor compression - hence loss of power.  It most likely is a clogged injector/s, but in my case it was the under performing injector pump.  
Before you change injectors or rebuild the old ones, remove the injectors and take them to a shop and have them checked.  They'll check the pressure, spray pattern and the tips for free.  Look in your Yellow Pages for a diesel engine injection sales & service shop.
 
Diesel injectors get clogged all of the time as diesel doesn't have the same solvent cleaning qualities as gasoline.  Hope it's a simple problem  like your injectors.