Out cruising Rauzer II this weekend and once again have the following problem. I am motoring along on smooth water at 2600 rpm when the engine starts varying rpm. It will waiver between 2400 and 2600. Sometimes dropping to 2500 then back to 2600. Then eventually steadying out again at 2600. It has happend before where the maximum rpm it will maintain is about 1800. Increasing the throttle only makes the variation worse. I thought it was the fuel filter in the past, so I would change the filter and it would then run fine for several hours of running, sometimes the remainder of the season then return the following spring. The manual says the filter should be "cleaned" every 250 hours and replaced if very dirty. When I replace the filter, the old one "looks" just fine. So, now I am suspecting the fuel pump may be going bad. Any thoughts or similar experiences out there?

You may also have water or diesel bug in the fuel. Water will plug up the pores in the filter. You can put in an additive for both water and diesel bug. I had diesel bug a couple years ago and finally ended up pumping out the tank to get rid of it.

What size primary and secondary filter element do you have? The filter on the 2GM just before the high pressure fuel pump is 2 microns. You should use a 10 micron filter before the fuel lift pump. I've got a Racor filter that has a manual pump on the top of it. When the filter starts to get plugged, you can hear the RPM drop and increase when manually pumping to pressurize the fuel system. You also might have a fuel lift pump (located on stbd side of engine) that is going bad. This has the handle on it so you can manually prime the system, but I've never been able to get that working effectively. I use the pump on the Racor to prime and bleed the system.

according to my diesel maintenance course, the lift pump should be replaced every 7 years due to potential deterioration of the rubber diaphram
I would agree with Bill, sounds like bad fuel or, restricted flow in the exhaust elbow

Taras

He Bill, I was just about to add an inline fuel priming pump; I'd much rather have one build into the filter.

I can't seem to find the one you are talking about just this:

http://www.westmarine.com/1/1/14607-fuel-filter-primer-pump-kit-from-racor-parker-filtrat.html

I assume thats not what you are talking about; do you have any information on the manual pump?

I was going to just install a hand bulb pump...

Thanks - Dan

Dan - the link you posted said the server was down for maintenance. Look at this link: http://www.maesco.com/products/racor/r_spn_intro/r_spn_mar/r_spn_assms/r_spn_assms.html and scroll down for model 215. That's what I have.

Here's a link to one on eBay

I just finished rebuilding my J/30 and redid the fuel system while I was at it. The previous owner had installed a second fuel pump presumably because they couldn't get pressure. As it turns out the problem was simple - the tank was dirty. If your tank is dirty, changing your filters will only solve your flow problems for a short time. Based on the fact that new filters work temporarily, I'd say this is almost certainly your issue.

I pulled my tank, removed the inspection port and was able to hand wipe out much of the tank by hand. Then I sloshed a half gallon of acetone a cup or so at a time to get the gunk out of the places where I couldn't reach. I pulled a TON of grime out of the tank! I got rid of the extra pump and the fuel pump on the side of the engine works great and I'm pretty sure my filters will last for a while now.

I ended up strapping the tank in so I could pull it and clean it fairly easily.

BTW: I couldn't be happier with my boat. New core in the bottom and decks, new epoxy bottom, fresh awlgrip, engine refit, etc. I've gotten a mountain of unsolicited compliments! Can't wait to do a little PHRF racing in my area to see how it stacks up.

Rich

#294 - Brass Monkey (Formerly Tres Cosas; I decided on a different name before I finished the project)

Follow up: I replaced the lift pump that was quite old, if not the original. The problem resurfaced so it looks like I need to clean the tank.
Questions; I had heard from a previous J30 owner that there were baffles in the tank. If so it would seem that cleaning it out would be more than just opening it up and wiping out the gunk. Has anyone come across that type of tank? Also, after the tank has been cleaned, do you need to flush the fuel lines? What do you use to reseal the inspection plate? Can the tank be cleaned in place, or does it need to be removed?
Thanks,

I became quite familiar with the fuel tank, fuel lines, and diesel bug from a couple long deliveries to the NA's years ago. After breaking down in Oyster Bay, City Island and the Hunts Point Trash depot across from LaGuardia airport, we ended up intermittently sailing and pumping fuel from a teakettle while traversing the rushing currents of Hell Gate and commercial traffic of the East River in NYC. I’d take a length of hose and portable fuel tank if I ever went on a long delivery again.

Our boat is a late model #481. There are no baffles in the fuel tank. You may need a hammer and screwdriver to open the inspection plate the first time. After that reseal only hand tight and you won't need one again. I routinely open ours to check the fuel level since the gauge quit years ago.

Be careful not to spill diesel below. It stains the floorboards and it takes ages for the diesel smell to dissipate. Once you pump or scoop the fuel out, you can get your arm in the tank up to your elbow to wipe it out. Leftover fuel can go into someone’s oil tank to heat their house this winter or your local recycling center.

Once you have had this problem you will get a Racor filter and never fill up again without using a diesel additive.

Hi I have a fuel tank like you're self which I had to clean out I removed it from the boat and poured some parafin into the tank and sloshed it about then emptied it and dried it out
I now use an additive and have had no further problem.

For those who are unaware of Jim Hoey's paraffin solution above, it is the UK equivalent of kerosene in the US.