How to: troubleshoot your marine diesel fuel system - Yachting Monthly - YouTube

Hello and welcome to Yachting Monthly's How-to series brought to you in

association with GJW Direct. I'm Matthew Sheehan and over the course of 13

episodes we're going to be dealing with some of the key issues when it comes to

maintenance and talking to some of the experts to get their tips.

So we've done right pre depart two checks but with the best will in the world

sometimes the engine still won't start. We're going see there are two main

probable culprits for that. The first is electrical and the second is fuel.

So what we'll do now is look at how we diagnose what the problem is and how we

can possibly get our engine started. To do that, let's go up to our test engine

where we can get a better sight of things.

Okay so one of the most common

causes of an engine not starting in the marine world is a fuel problem. Some say

up to 80 percent of all problems are fuel related. So if that's the case, what

we need to do is just start from the beginning

and work your way methodically through the system. First does your fuel tank

have fuel in it? The fact that gauge is showing something doesn't necessarily

mean that's the case – gauges can be faulty. For our test engine it's very

easy to see but just be aware: do you have fuel? Next is the fuel shut-off open

or closed? If the boats been stored for the winter or someone else has used the

boat it might well be that they've closed the fuel shut-off. So let's make

sure that that is open. The next thing you're going to come to is some form of

pre-filter on your engine. These come in various shapes and sizes, but they all do

much the same thing. They have two functions: firstly to remove the large

bits of debris that might have come into the fuel, and secondly to separate any

water from condensation or water ingress that has come in to the fuel. We have a

nice glass container here so we can see. Sometimes there is a

metal container. What you need to do if you can't see it visually is use the

little tap that you'll always find on the bottom. Drain out some of the fuel

into a container and just check for whether there's any water in it.

It's very obvious if there is – you can see the separation between the water and the

diesel. In this instance we've got a nice glass one here, we can see it very

clearly. There's no water in that fuel.

The next stage in the fuel process is the fine filter. This is the last stage

of filtration or protection of the engine before the fuel goes into the

high-pressure pump and it's here that you'll often find that you need to bleed

the engine if it's run out of fuel previously. Now again each one of these

filters are slightly different but looking in your manual you should be

able to quite easily find where the bleed point is.

What we're going to do here is open the bleed system to allow any air out of the system. We'll manually pump

the fuel and we'll see fuel coming out of here and we'll keep going until there

are no bubbles in it. So on this engine here's our manual lift pump and you'll

see it has a little lever which allows us to pump the fuel manually into the

fuel filter. So let's see how this works.

Okay so we've seen that our engine's not

starting and we suspect there might be air in the fuel so we need to come to

our bleed point of our fuel filter. Take some rag or some special oil soak that

you can buy. Put it under there to keep your engine and your bilges nice and clean.

Now what you need to do is open the bleed point

to allow fuel to flow out the top of the filter.

Then we're going use the lift pump and start giving the pump

a good going-over.

Now what we can see here as we pump it

is lots of bubbles coming out and this is a sure sign so there's some air in

the system. So we're going to keep pumping this until we see nice clean

diesel without any bubbles in it.

So we've been pumping this for a while now. There's no more bubbles coming out

of it, just clean fuel, so we can be really comfortable that there's no more

air in the system. We're going to tighten it back up and we should be good to start the engine.

Nice and tight. Remove the rag, clean up any last drips that may have come there.

Give it a good cleanup

and we'll see if that's helped to start the engine.

The engine started really nicely this time. It was a fuel problem, and we've solved it.

Now if you have suffered severe fuel contamination,

maybe you have significant amounts of water in it, a lot of debris in it, or the

dreaded diesel bug, there is a technique you can use hopefully to get you home

and that is simply to disconnect your fuel system from the tank. On our test

engine here, we have the feed into the filter here. We would disconnect the hose here

and we would simply put it into a jerry can of clean fuel. That bypasses

any contamination you've had and should be able to get you home until you can

get proper repairs done.

Well thanks for watching. I hope that was a help.

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