Diaphragm Lift Pump Life

[wingssail]

Originally Posted by ColIn Ferguson

...Not sure how diesel would get from a pump failure into the sump oil ...

On his engine I believe that the fuel pump is operated by a lever from the cam shaft and which comes into the pump through a hole in the side of the engine block, open to the sump. One side of that diaphragm is fuel under pressure and the other is open to the sump. As the lever pressed up and down on the diaphragm a leak in the diaphragm allows pressurized fuel to spray into the sump.

[Tin Tin]

Originally Posted by FPNC

Most small diesel mechanical lift pumps are designed for tractor or generator applications that are designed to operate with very little lift and a short distance from the tank. Many tractors have the fuel tank above the lift pump so there is no lift at all. IF your vessel has fuel tanks well below the engine or far from the engine, you are asking the little lift pump to operate in a manner that it was not designed. Expect a shorter life expectancy from the diaphragm and less fuel flow. Fuel flow is important as even if the fuel is not burned, the excess fuel is intended to cool the fuel pump and injectors as it returns to the tank.

Agree. We had an Onan generator with standard lift pump situated about 5 ft above the fuel tank, there was an additional little lift pump also installed in the line just below the engine. The engine lift pump lasted about 1500 hrs (3 yrs) - replaced it with a higher lift Facet Cube that worked well.

[skipperpete]

Getting back to the OP Where the oil sample returned a positive for fuel oil contamination…. I’ve been trying to get a GM series yanmar to start for about 6 hours in total so far. The problems have been various, mostly battery and cranking speed but also 1 squirty injector. The engine is out where its easy to work on with no exhaust attached. The extended dead cranking and a crook injector has flooded the cylinders to the point that I had raw fuel coming out of the exhaust and I bet that some made it past the rings into the lube oil since these engines have flat crown pistons with no place for the excess fuel to lay (unlike the 4JH with recessed crowns) this causes me to be even more wary of oil sampling but still not dismissive.

[sailingharry]

Originally Posted by Shanachie

It's like oil changes. Yeah, you can probably go 150 or 200 hours without damage to the diesel. But why? Change it every 50 to 100 hours and know that you are not damaging the diesel.

Interesting view. That's five times as often as recommended by the manufacturer. And my experience, as well as other comments I've read here and elsewhere, is that oil analysis indicates that the manufacturers recommendation is somewhat conservative. Oil samples at the 250 hour mark tend to be clean with ample levels of additives remaining.

Do you typically do most of your engine maintenance so frequently? Yanmar recommends annual coolant change, do you replace yours twice a season? Impellers are changed by many people annually, do you do yours twice a year?

And why do you go 50 hours, or even stretch it to 100? It should be easy enough to schedule it for every month (or weekly, if you use it more than 10 or 20 hours a week)

Last summer, I put 600 hours on the engine. I carried three full oil changes with me, knowing I would probably need two and carrying one extra. 12 changes of engine oil would have been a pain to carry! Three oil changes a month would have been a lot of work, not to mention the challenges of disposing of that oil in remote places!

[NBs]

Hi,

diesel oil can also be used for short periods where the engine does not warm up enough or you load it too lightly and the fuel starts to accumulate in the oil.

NBs

[sailorboy1]

barely anyone on topic really

[Shanachie]

Originally Posted by sailingharry

Do you typically do most of your engine maintenance so frequently? Yanmar recommends annual coolant change, do you replace yours twice a season? Impellers are changed by many people annually, do you do yours twice a year?

And why do you go 50 hours, or even stretch it to 100? It should be easy enough to schedule it for every month (or weekly, if you use it more than 10 or 20 hours a week)

!

This is off topic, but answering an off topic question.


I assume from your message that you are a powerboater. I am a sailor. Way different circumstances when it comes to changing oil.


Diesel engines on sailboats mostly run for short periods of time at relatively low speeds in canals, entering and leaving marinas, etc. Diesels on powerboats run at 75 percent power for long periods, if you know how to treat them.


Sailboat diesels will collect much more goop and contaminants in the oil with short, low-speed runs.



Ford, for example, recommends changing the oil on its diesels every 10,000 miles if you mostly drive highways. At perhaps 70 mph average, that's roughly 150 hours.


If you drive stop and go, it recommends every 3-5,000 miles. At 30-40 mph average, that's 100 hours.



Cynic that I am, I suspect that the 250 hours your diesel manufacturer recommends is the maximum period, not the minimum. After all, it is in the business of selling you replacement parts and new engines.


My basic point is that regular oil changes, like changing fuel pumps occasionally, is an inexpensive way to avoid catastrophic situations.

[Shaneesprit]

Originally Posted by ColIn Ferguson

I have had two lift pumps fail, both at about 35 years and 5000 hours. Both were due to diaphragm failure, one stopped pumping and the other sucked in air. Cheap and easy replacement and I now carry an electric pump for emergency use.
Not sure how diesel would get from a pump failure into the sump oil. On an engine this old it is more likely that there is some piston ring leakage.
I have never done an engine oil analysis as i don't know what I would do with the result, other than worry a bit.
I am of the "if it ain't broke don't fix it", but carry spares for early failure parts. I have had more problems from poor preventative maintenance than regular usage and observation.

Oil leakage through the piston ring leakage happens regardless of engine age, it’s due to lack of expansion, caused by lack of heat & pressure caused by lack of engine load.
I have seen this on engines within their first few months. Nothing wrong with them just badly sized or badly used.

[sailingharry]

Originally Posted by Shanachie

I assume from your message that you are a powerboater. I am a sailor. Way different circumstances when it comes to changing oil.

Actually, I'm a sailboater. I'd have racked up a lot fewer hours as a power boater (at 10-15 kts compared to my 6-7 knots). 4000 miles, much of it in rivers/canals, with a 4 month schedule, leads to more motoring than desired. 4000 miles in 120 days is a 33 nm daily average -- before sightseeing and weather delays. You can't poke along at 4 knots on a nice day (even worse it it is upwind) if you want to keep your days under 8 hours (so you get into port in time to actually see the place you are stopping at!).

[sailingharry]

Originally Posted by sailorboy1

Since the engine is pretty old with a fair number of hours I wonder if I should just replace the lift pump. An aftermarket one is only $34 and it may be worth rebuilding the OEM. Then again maybe should just replace it with an electric pump.

OK, so back on topic.... sorry about that....


I have essentially the same engine, the 4JH2E. I suffer from an air leak someplace in my supply line, that I've been unable to isolate. After a week of engine off, it can take 30 seconds of cranking to get the engine going again. I apparently reduced the leak, because it used to be so bad the engine would die at idle. A tip that helped me some is inserting a short clear piece of fuel rated tubing between the lift pump and the injector pump, and I could see the bubbles. UGH!


Anyway, as part of that, I became convinced it could be a leak in the fuel pump diaphragm. I replaced the fuel pump (not the solution) with a compatible pump, at about $35 or so (same price point you are considering). It's run about 1,000 hours over the last 2 years or so, with no apparent ill outcomes. My original Yanmar is in the spares box.


So the question I ponder, and you should too. My pump was 20+ years old, with 4000 hours on it, when I replaced it (for no good reason). I have concerns about the comparable longevity of a $35 aftermarket diaphragm (the only part I'd worry about) when compared to a $150 Yanmar pump that both you and I and a gazillion others have seen 20+ years from. Note, I still have that unit in service.

[sailorboy1]

Originally Posted by sailingharry

So the question I ponder, and you should too. My pump was 20+ years old, with 4000 hours on it, when I replaced it (for no good reason). I have concerns about the comparable longevity of a $35 aftermarket diaphragm (the only part I'd worry about) when compared to a $150 Yanmar pump that both you and I and a gazillion others have seen 20+ years from. Note, I still have that unit in service.

I am not very worried about using a $35 aftermarket lift pump instead of a $200 Yanmar one made by who knows for Yanmar. You have any idea how many 4JH3 engines are out there in the tractor equipment use world???

I was told that same thing about replacing my burnt up starter here on CF about 10 years ago. People said I needed a $450 OEM unit because the $95 aftermarket one would not last. Well the aftermarket is still working and has been installed longer than OEM was.

[sailingharry]

Originally Posted by sailorboy1

I am not very worried about using a $35 aftermarket lift pump instead of a $200 Yanmar one made by who knows for Yanmar. You have any idea how many 4JH3 engines are out there in the tractor equipment use world???

I was told that same thing about replacing my burnt up starter here on CF about 10 years ago. People said I needed a $450 OEM unit because the $95 aftermarket one would not last. Well the aftermarket is still working and has been installed longer than OEM was.

Don't get me wrong. I bought the $35 unit, and it's got 1,000 hours on it and I'm not taking it out. But I do sometimes wonder.


I bought a rebuild kit off Amazon, cheapest possible, for my old Mercury outboard. In under a week, the gaskets had swollen to the point that it no longer worked -- apparently the material wasn't compatible with gasoline..... I bought a Sierra kit and it worked great -- I stuffed all the bad parts in a zip lock and sent it back to Amazon for a full refund! Most aftermarket stuff is just fine. Trying to figure out which ones aren't is the fun part!

[skipperpete]

Well, while the feed pump on a 3GM has a diaphragm that can’t be changed, the Mikuni pump that’s attached to the side of the 4JHE injector pump apparently can, I’m not sure about the 4JH3E. I don’t have a parts catalogue, just a service manual and it specifically mentions replacing the feed pump diaphragm so if you have the little Mikuni on your engine, you’re in luck.

[sailorboy1]

With a whole costing $34 why would want to replace the diaphragm?

[jvolpehoo]

my bilge had about a gallon of fuel diesel in it and it was a failed lift pump on a yanmar 2GM. I had read that you can throw a lit match on diesel and it would burn like a candle wick...but I was pretty freaked out at all that fuel sitting under a hot engine!... I bought a new yanmar lift pump, not too expensive and an easy install...after soaking up all the fuel with absorbent pads