28TE fuel starvation

[robin]

I wonder if anyone with a 28TE with a Yanmar 6LPA-STP (2005) has had a similar problem. Several months ago, during a rough crossing with 1/4 tank of fuel, the engine began to lose power from its normal cruise RPM of 3,250, eventually bottoming out at between 1600 and 2000RPM. About every 30 seconds it would increase to 2,000, then settle back to 1,600. It repeated this cycle for over an hour. The throttle was not touched and did not move, and remained in the location at which I normally would see 3,250. Engine time 780 hrs, time since fuel filter replacement 70 hrs (Racor and Yanmar). The engine never ran roughly, never sputtered or died, but ran as if there was an invisible hand playing with the throttle, although the lever never moved.

Both filters were inspected and changed, but they really didn't look bad. I filled the tank, "shock-treated" the fuel with Racor additive, and headed back out on a calmer day. The boat ran perfectly, and continued to run without any problems for the next 35 hours. Then I began to notice that it wouldn't come up to full cruise RPM on the first attempt...it would balk at 2,800-3,000, but a minute or two later, it would run on up to 3,250 and stay there for the entire 2-hour trip. Yesterday my luck ran out (again). It was cruising fine at 3,250 until I went though some large wakes, which caused it to fall back to 3,000. Within two minutes I was back up to 3,250. I intentionally went through another series of wakes a few minutes later and it repeated the drop and recovery. But ten minutes later it began to fall off to 2,600 and would not come back to cruise again, even in flat water. I pulled the throttle back to idle, put it in neutral, and it revved to 4,000 easily. But back in gear, it wouldn't surpass 2,600.

It seems unlikely that either filter is at fault, at barely 35 hours since replacement, so am thinking that the tank must have enough accumulated crud on the bottom that the fuel line pick-up is being partially and/or intermittently plugged. The tank (162 gallon) has no inspection/clean-out port. Has anyone taken the fuel line off the tank, backed out the fitting, and looked at the pick-up? I tried to back it off, but I couldn't budge it. Is there a filter on the end that would plug up if there was crud building up on the bottom of the tank? Would you recommend getting rid of that filter entirely, and letting the Racor and the engine-mounted Yanmar filter do what they are supposed to do? Has anyone gone through the fuel-polishing/tank cleaning routine? How can the tank be cleaned without an access port?

Any experience or advice would be appreciated.

[N4QC]

Check out the link on this site for possible sources of restricted fuel flow:

viewtopic.php?f=7&t=7606

Successfully fuel polished my 144 gal tank on an 24' Getaway, by removing the fuel tank gauge assembly...

Your Racor fuel filter, if it is an older 500FG, may have filtering issues solved by a special "o" ring... If it is a 500FG it is probably under sized for you engine configuration.

Main suspect at this time is air intrusion into the fuel supply system from the tank to the output of the filter on the engine...

Recommend adding a fuel vacuum gauge with a pointer to your system... See http://www.designatedengineer.com
for gauges and a discussion on the 500 series racor "o" ring problem...

Happy researching,

[Jack]

Crud in the fuel is my guess. I had a problem with stalling at high speed but less problem off plane. Tilting the crud into the system on plane was the problem. If you had your fuel pumped and filtered you should have solved the problem. I wonder if they did it well.

[robin]

Thanks for those ideas. A gauge would certainly be a good addition, whatever the problem turns out to be. To clarify, I have not had the fuel polished...yet. And the filter is a Racor 900, not a 500.

[jleonard]

Pull the filter element and post a couple of pics. What micron rating is it?
I have had fuel lines plug in the past the enemy looked like large coffee grounds they got caught in the fittings where the male flares were machined (smallest part).
But I'm still guessing clogged filter

[special k]

had my 6lpa-stp behave like it was starving for fuel/not reaching full rpm's. mechanics could not pin point the problem and i would not give free reign @ $120 per hour.

i asked around for a full season before i found a capt. with same issue and he directed me to the boost pump diaphragm. removed cover (very easy) found rusty water and clogged vacuum tube. cleaned, dried. and snaked out clogged vacuum nipple. do a search on 6lpa-stp not getting full power here i put up a photo of the offending device. well worth a try and hopefully an easy fix.

cheers!

[robin]

Thanks, Special K. I tried to search "6lpa-stp not getting full power" and was told that there were "no results because the word 6lpa-stp does not appear in any posts". Great search engine. I finally found your earlier thread but was told that I "did not have permission" to look at the picture, even though still signed in. So I tried to look it up in the service manual, but didn't find the term "boost pump". Are you talking about the fuel pump, or something in the turbocharger system? And to answer a previous query, the Racor filter is 10 microns.

[Carl]

search.php?keywords=+6lpa+not+getting+full+power+




Try this link or just rtemove the "stp" from the search. I run a 30 micron Racor, as the Yanmar filter on the engine is 10 micron.

[special k]

perhaps some photo viewing is for supporting members?? buy a coozie!

[RobS]

... Are you talking about the fuel pump, or something in the turbocharger system?...

It's atop the injection pump, right above the throttle lever linkage.

[robin]

Mystery solved! It was the wire mesh screen on the end of the fuel pick-up...totally blocked with fine, hardened crud. Cut it off, threw it away (it was glued on and can't be replaced), and cut two inverted-V notches at the bottom of the tube. It's amazing that the boat ran at all with only a few pinholes letting fuel in.

But the most amazing thing was discovering a jaw-droppingly stupid feature of this otherwise wonderful boat. You can't perform the simple fix I did today - removing and replacing the fuel pick-up hose - unless you have less than half a tank of fuel. The fitting sits atop the mid-tank flat area, not on the top of the tank, although there is plenty of room for it on top. Any more than half a tank of fuel would gush out the open hole when you pull out the pick-up tube. So be sure to have this common problem BEFORE you fill up. And always stay close to a major marina where you can get pump-out service. Great design. Thanks, Albin.

[special k]

there is no such thing as the "perfect" boat. for a production/semi-custom boat in the moderate price range i love my 2002 28te albin even with all it's flaws. every boat is different from wiring to plumbing. however, i do hope i never have to replace any windshield glass. glad you were able to pinpoint your fuel issues.