As with all things in life, everything goes well until it doesn’t. It is an inevitable truth that something will go wrong eventually and will need some TLC! Taking precautions with regular and preventative maintenance will certainly help prolong the time interval between any issues. When it comes to our beloved engines, however, all the preventative maintenance can’t prevent the invisible wear and tear on various components. This wear can result in a broken water pump impeller or, as in the case of this true-story, a worn-out fuel lift pump.
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Anyone know the techincal rationale for the loop trap on the return line?
Hi Ben, not sure what you are referring to by the term “Loop Trap”. But in basic terms, the fuel return line, which picks up “excess” fuel after the injectors, to makes it’s way back to the fuel tank. Nor sure, but I hope this answers your question. Have a great day and thanks for your comment.
Information on the lift pump is extremely valuable.
I’ve had two electric lift pumps fail in my sailing career. They’re more easily diagnosed because there’s no “click” or pumping sound when I turn the key. I was able to get a replacement from the engine manufacturer (Westerbeke) in a few days the first time. I also bought a spare which saved the day the second. I wish they were cheap like these mechanical units. Over $200 OEM! Westerbeke W46 and now 55D.
Thanks for this and all the other articles. I’ve been a subscriber from the beginning, and credit PS more than any other source for information making my sailing safe, fun and economical.
Bob
The above diagnostic procedure has a couple of faults: 1) “loosen each injector fuel line, one by one, and turn over the engine (with the kill switch on this time).” No! The kill switch cuts off fuel to the HP pump, stopping the engine when engaged. 2) “Normally, there should be lots of fuel at high pressure. So, now we knew it was the fuel-lift pump for sure.” No, again! Given that the kill switch was engaged, there will be no or v. little fuel from the injectors, so, no, the test does not condemn the lift pump; what about the HP pump? It could indicate the same symptoms.
Having a vacuum gauge is very helpful. It indicates the amount of negative pressure (suction) it takes to get the fuel from the tank to the lift pump. I have found this to be a useful diagnostic tool, especially when the primary filter is clogging up.
To diagnose the problem, start from the fuel tank and end at the injectors. That said, in some cases, it may be easier to go for the “usual suspects,” as you did by changing the filters. If you lack or are unsure of your diagnostic skills, you can use the R&R (remove & replace) method until it’s fixed or you run out of money!
Is it possible for a fuel lift pump to fail partially time? I recently ran out of fuel with six gallons of diesel left in the 36 gallon capacity tank. Both of the fuel filters are clean. I am wondering whether the fuel lift pump was no longer able to pull fuel from the tank due to the decreased volume.
Hi Clarke, good question and yes, it is possible. As a matter of fact, in retrospective, mine was showing signs for a while. But it was only by diagnosis and process of elimination. If your filters are for sure clean, the lift pump, by what you describe, would definitely be the next and likely, culprit.