Replaced filter, engine no longer revs high. Why?

[stillbuilding]

Well this sounds like my 4BT Cummins which has caused me no end of grief and turns out that the lift pump just cannot the pull up from the integral keel tanks (only 3'). With a fuel pump running constantly it manages fine but switch it off and the motor stalls or usually stops.

I agree with the suggestion to install a minimal filter from tank take off, then fuel pump with suitable pressure, then Racors and then to the last filter and engine lift pump.

I suppose a vacuum valve may be informative.
I had a day tank above the motor as a trial - did not help, which does not make sense I know- maybe is sucking a little air as previous suggested ? No evidence of a leak but maybe just enough to let air in but no fuel out. Hmmm


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[antoha]

DeepFrz: i don't have the tools to measure temp on the prop shaft stuffing box. the best i can do is count dripping frequency, which i'll try to do next time. but: why would a fouled prop have the effect of not letting the engine go to high rpm?

transmitterdan: i used white teflon tape, a couple of turns on each male fitting end except the racor native ones which go into the housing (they have o-rings on them, so i was under the imperssion that's sufficient - is it?). i know racor explicitly says not to use tape but i couldn't find anything else in the hardware store at that time. what is best to use?

about leaks and all: i was under the impression that air leak would most likely result in stalling on idle, but i do not see that.

[leftbrainstuff]

Originally Posted by antoha

i just replaced my old racor 200 with a racor 500. the engine is a westerbeke 35c-three, with under 300 hrs on it. have been having fuel delivery problems with it ever since we got the boat (burnt out 3 lift pumps), tank is deep in the bilge so i have close to 5-6 feet of lift from bottom of tank to lift pump. so i decided to change to a filter which restricts flow less.

so all is good, dockside the diesel runs fine, both at high rpm (2500) and at idle (<900), doesn't choke, no fuel leaks. but put the load on - and it doesn't go above 2000 rpm. what could be going on?

compared to last year all that's different is: i added more fuel (a couple of 5 gal jerry cans, bought at a local car gas station; the mixture is no longer deep red but light orange - still has pigment though); i tightened the packing gland just a little so it drips less (but it still drips when shaft is spinning); i replaced the fuel filter as described above. primary filter is 10 micron 2010 element, brand new. i did not change the secondary filter.

any advice or suggestions will be greatly appreciated!
thank you!
Anton

Vacuum gauge between the filter and your lift pump will help you to diagnose.

Have you replaced all hoses. Sometimes they can delaminate internally and cause intermittent blockages.

What about the pickup in the tank. Is that clear?

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[antoha]

i did not replace the hoses - saw no need for that since it was working fine before i upgraded the filter housing.

[DeepFrz]

DeepFrz: i don't have the tools to measure temp on the prop shaft stuffing box. the best i can do is count dripping frequency, which i'll try to do next time. but: why would a fouled prop have the effect of not letting the engine go to high rpm?

You can check your stuffing box temp. with your hand after running a while. It should be no hotter than warm to the touch. Usually the drips are a good indication but it doesn't hurt to double check.

If the prop is heavily fouled it will load down the engine which can't get to full RPM. Usually accompanied by black smoke at full throttle.

[CLady]

Wouldn't it be good to mount the vacuum gauge somewhere quickly visible so that it isn't required to get down into the engine compartment, or any compartment, just to see the vacuum gauge reading while under way? The vacuum gauge is helpful--filters can become clogged with water, sludge, etc., from a fouled tank when out on rougher seas, and seeing if a vacuum is starting to get pulled would be helpful in checking the filter sooner than later.

I hope this helps.
C Lady

[hamburking]

Check your air filter!

[Limitless37]

Check the installation instructions, it mentions the Racor 500 does not do well with too many bends 90's or 45's. You might need to simplify your install.
I am in the process of changing or upgrading my Racor 200 to the 500 as well.
Good luck!

[Crabby1]

The next test I would do is quick and easy; sit a jerry can of filtered diesel above the engine. Put fuel line straight from can to filter inlet, check for fuel leaks (gravity fed system will not have air leaks). You could also bypass filter by running fuel hose go straight to engine (filtered diesel), but I would hookup before filter and other connections to see if where I was sucking air is now leaking fuel. Run engine see if rpms are up... If rpms are not up, problem is gonna be elsewhere fouled prop & bottom.

I wish every boat builder would figure out how to install a simple trouble free gravity feed fuel system.

[antoha]

DeepFrz: huh, didn't think about it. how long does one have to motor before the stuffing box temp rises enough to be detectable this way?

C Lady: it would, but i have no room. this is why i got a gauge with a drag needle (it will tell me not just the current reading but the limiting value since whenever), so i won't need to check it while engine is running. MaineSail has an article about it. but you're right, and if i can come up with a way to mount the gauge so i can always see it, i will.

hamburking: interesting, i will, thank you. i didn't interfere with that path though, so wonder why there would be more restriction in the air intake.

[antoha]

Limitless: other than the additional 3/8" to 1/4" reducers, all the other fittings are same as before. so my mantra does not change: "if everything (except for what i think should be better now) is same, why should things get worse?" yes, there are other possible problems (air intake, water intake, bad fuel, clogged this and that) - but i didn't change these parameters since last season. prop - yes, could have fouled up, stuff grows.

Crabby: as to the test you're suggesting: i will see how i can do that. but if the problem is that the hose fitting on the fuel line going from tank to the racor is not screwed on tight enough, i wouldn't be able to test that - since i'd be changing that attachment point to go through the alternative path.

as to a simple trouble free fuel delivery system: would be nice, but the boat is from 1968, and i'm pretty certain they did what made sense to them at that time.

[Crabby1]

"Crabby: as to the test you're suggesting: i will see how i can do that. but if the problem is that the hose fitting on the fuel line going from tank to the racor is not screwed on tight enough, i wouldn't be able to test that - since i'd be changing that attachment point to go through the alternative path"

You WOULD be testing that by this process. If the rpms go up you will know you HAD air getting into fuel system, and now you KNOW what the problem is and your not chasing your tail no more

[antoha]

Crabby: you're right. i meant that it wouldn't help me distinguish between the 2 cases: (a) did i simply not tighten the fittings? (b) is the fitting no good.
so when i switch back to the original setup, i may have the same issue even if i fix everything else downstream from that fitting.

[Crabby1]

Most likely the fitting is good. The installers may have used a hose a little too big or a fitting too small. Old hose could be used and little stiff and not sealing completely around fitting. The canister may be leaking, at any fitting or around the ring. You suck air a whole lot easier than leak fuel. Thats the whole problem with tank below motor; its a compromise to have space and design the builder wants.

All that said I still think its a real good possibility of a fouled prop with the engine running smooth at 2000 rpms and maybe a little growth on the hull. This test will quickly tell you.

Also is the canister staying full of diesel?

[antoha]

from what i can tell - no added smell or dripping. and the bowl stays full.

speaking of goop: what to use? permatex 2? and do i need it on the fittings that go into the racor housing?

the fittings on the hoses are those pivoting compression fittings - when it's not tight enough, the leak but not from the attachment point but somehow behind the articulation; when tightened, that stops. the hoses are 5/16", while the fittings are 1/4".