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Old 06-08-2010, 12:24   #1
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Air Leak and Lift Pump, 2GMF

Im in the process of fighting what I believe is an air leak on my 2GMF. The engine runs great after bleeding (sounds good and lots of power). After running for ~15 min under load the RPM drops off and the engine looses power. If I open the Racor filter housing its full of air. I have changed both fuel filters with no difference in performance and there is no evidence of diesel in the crankcase. My plan is to replace all the fuel hose on the suction side of the lift pump, remove and examine the lift pump (dont know how old it is) and replace all banjo bolt washers. I will also pull and check the pick-up tube to see if it has a screen (hope I can get it out). Is there anything else I should check or rule out first? If the lift pump is bad I would rather replace it with an electric pump. Is the there a recommended pump? Would I need a return line before the injection pump.
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Old 06-08-2010, 12:53   #2
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If racor filter is before lift pump you have leak in hoses or filter (check and tighten clamps)to tank.If filter is after pump leak is between pump and filter.In the second case you should also have fuel leakage when running.My boat has water seperator in line from tank and electric pump to use when starting engine then lift pump and second filter on engine.Do not reccomend running boat on electric pump except for starting.
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Old 06-08-2010, 13:05   #3
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Remove to workbench to inspect the Racor filter seats and seals. I've had QC problems in that area.
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Old 06-08-2010, 17:00   #4
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Most lift pumps are diaphragm pumps with a pumping lever that is inserted inside the engine. The top/bottom of the lift pump has a "cover" that when removed exposes the rubber diaphragm. It happens sometimes that the cover or the bolt holding the cover will allow air to be sucked into the fuel stream.
- - Also check each fuel "pipe" - not the hoses - for worn or fractured collars where they go into the various parts of the engine.
- - If the a Racor(s) are letting in air then check the lift off covers where the rubber large O-ring is inserted. It is a common problem with Racors that the paint that was sprayed on them during manufacture accumulates in or next to this O-ring recess and prevents the caps from fully seating properly.
- - As another has mentioned check hoses and hose barb fittings for leaks. I always use the paste type pipe sealant versus teflon tape for fuel fittings. Since the whole fuel supply system before the lift pump is a suction system the teflon can allow air to enter whereas the pipe paste (fuel rated) will flow into any micro-passages and seal.
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Old 07-08-2010, 11:18   #5
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Update

Thanks to all for their replies. I pulled all the fuel line from the lift pump to the pick-up tube. The 25 year old tubing looked ok until it was moved in anyway. It showed cracks in the surface, mainly at bends. This was especially evident near the inlet to the Racor. Will replace the fuel line. I remove the lift pump. It’s appears to be ok. It was damp with what I assume was fuel. The banjo bolts were not loose, but not tight either. Will replace the washers. The other thing was that when I was removing the fuel line from the pick-up tube the hose barb fitting broke off. By the looks of it, it may have been cracked. This would explain a lot. But, the real annoying thing is there is not enough room to remove the pick-up tube from the tank. Why would anyone design something like that is beyond me. I wanted to pull the pick-up tube to see if had a screen. At least I have room to use an easy out on top of the tank.
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Old 07-08-2010, 21:03   #6
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Why would anyone design something like that is beyond me.

They have never owned a boat.....that's why.

How big is the tank? Location?
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Old 07-08-2010, 21:04   #7
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Just a thought...is the racor a new installation.....if so there IS an IN and OUT side.

Not trying to be funny....but one must remove all possibilities.
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Old 07-08-2010, 21:43   #8
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Chief,
The tank is 24 x 18 x 12 under the cockpit, behind the engine with 11 clearance between the tank and the cockpit. I thought about cutting off the bottom 1/3 of the pick-up tube (with a string connected to the bottom piece for retrieval). I could then replace the bottom part with something flexible or replace the whole $$*^&^ thing. Any thoughts? Oh!, the Racor is not newly installed
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Old 18-08-2010, 10:16   #9
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Quote:
Originally Posted by riptide View Post
.............My boat has water seperator in line from tank and electric pump to use when starting engine then lift pump and second filter on engine.Do not reccomend running boat on electric pump except for starting.
I have a squeeze bulb in fuel line after Primary racor filter on my Yanmar 3GM30's. This has worked well for bleeding the fuel lines to the secondary fuel filter. However I am wondering if I install a Facet electric fuel pump instead of the primer bulb will I be able to bleed fuel all the way to the injectors? I read that the electric fuel pump could also be used to run the engine if the Yanmar's fuel pump was to fail. What sort of problems would this create?

I have also found that the 3GM30 does not need the injectors cracked and bled even if the engine has run out of fuel. Is there any problem in not bleeding the fuel lines past the Yanmar high pressure fuel pump?
thanks for the advice.
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Old 24-08-2010, 21:35   #10
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I have a 3HMF that runs well. Fuel from the main tank is pumped through a Racor filter and then into a 3 gallon feed tank that gravity feeds to the fuel infeed pump, then through Yanmar fuel filter and on to fuel injection pump. System works well.

Steve Twitty
s/v Bucephalus
Phuket, Thailand
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Old 25-08-2010, 15:33   #11
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I know may people recommend a squeeze bulb, in line to make bleeding the system simpler, and it likely works well. But, I believe I read somewhere here that thye may not be up to code, so to speak, for use inside an engine compartment. This may put you at some risk, if ever there was a fire / insurance claim, etc.
Most squeeze bulbs I have seen are for outboard engine use, and I believe has some warning to that effect. To each his own.

For the few times I have to bleed the system, the manual lift pump works fine. If it doesn't seem to work, lift your decompression levers, turn the engine over manual one crank, and try again, as the cam may not be in the correct position / stroke. As well, it is deceiving as the lift pump does nothing throughout about the first 3/4 of it's stroke, and then pumps during the last little push on the lever.
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Old 25-08-2010, 16:08   #12
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my mechanic said you only need to prime up to the fuel pump .. where there is a bleed fitting. the squeeze bulb i have is rated for diesel.
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Old 25-08-2010, 20:37   #13
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Northeaster: Thanks for the input. I did not consider the regulations pertaining to a secondary fuel tank in the engine compartment. This tank was fitted in the South Pacific, several years ago. Going back to a direct feed system is probably the best option. Happy sailing.
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Old 25-08-2010, 22:36   #14
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Quote:
Originally Posted by riptide View Post
Do not reccomend running boat on electric pump except for starting.
Why?

My 3gm30 has an electric fuel pump which works quite well.

Took a class at Mack Boring. The instructor said that it was a perfectly acceptable setup to have an electric fuel pump in the system.

I don't see a downside, unless I am missing something.
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Old 26-08-2010, 02:16   #15
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Phantomracer, I think the issue is having a secondary fuel tank within or close to the engine compartment. My secondary tank is on a partial bulkhead between the engine and the transmission, below the galley sink. If indeed there were a fire in the engine compartment, the secondary tank could add to the problem.
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