Checking fuel pump

[Fab1]

Hi guys, just a quick one on how to check your fuel pump is operational and a way of checking for water contamination in fuel for the diyers.

This will apply to basically all 2 stroke carburettor outboards in all hp classes that use a mechanical fuel pump.

A mechanical fuel pump will fail normally due to fatigue or rupturing of the diaphragm membrane after many hours of use causing drivability issues with your outboard one of which can be spark plugs that foul as in my case.

The fuel is usually mounted to the side of the outboard.

Here I have removed the 3 fuel hoses and 2 mounting bolts and its ready for surgery.

Please note that when pulling apart fuel pumps,carburettors etc that its good practice to renew all gaskets when putting back together.

Saying that, with a little care taken on your part you can re-use old gaskets without issue as I've done for years.(It's not hard to make your own gaskets either but that's for another post).

Here I have removed the top cover exposing the rubber diaphragm .

It is this that will eventually tear,rupture,split etc that usually needs replacing.

Here I have removed the diaphragm from the fuel pump exposing the one way valves which are those silver vanes you see.

Now is the time to have a close inspection of that diaphragm looking for the signs mentioned previously holding it up in good light.If you can see pinholes through it or any thing else discard it and install a new one.

Here is a closer look at one of the valves still installed and removed from the fuel pump.They are quite fragile and can break or move out of position so inspect them also that they are in one piece and located in their seats properly.

Here is a shot of the valves seat showing the port fuel flows through.

Here is the backside of the fuel pump with the cover removed showing a plastic membrane which again should be intact as before and the opposite valve in the main part of the pumps body clearly seen.

It is good practice to put hose clamps back on in the exact spot they were originally as indicated by the grove in the hose to prevent leakage occurring.

Here I've reassembled the fuel pump ready for installation back onto the engine.

The fuel pump mount on the engine block(The gasket is in serviceable condition).

Ok it's time to check for water in the fuel.

I like to check for water in the fuel filter while checking for debris also.

Here my fuel filter is mounted beside the fuel pump.

Here I've removed the fuel filter housing entirely from the engine by removing one mounting nut and disconnecting the 2 inlet/outlet fuel hoses.(you can see the filter inside the bowl).

Here I've unscrewed the bowl by hand from the housing exposing the mesh fuel filter.(I have emptied the fuel out of the bowl in a clear container to inspect for water later)

The fuel filter simply pulls off its housing.

You want to inspect this for debris as debris will restrict your fuel flow starving your engine of fuel.In my case mine was spotless.

You also want to inspect the fuel filter bowl for debris and check the condition of the sealing ring is in good condition.Again mine was pretty much perfect except for the tiniest bit of debris.

Having a look at the fuel I saved earlier when I emptied the fuel from the bowl earlier you can clearly see that the fuel is a uniform colour with no bubbles or separation to be seen in the fuel sample.

Here I have added water on purpose to my sample to show you guys what water contamination in fuel looks like and you can clearly see that now you can see bubbles and the fuel is separated from the water and sitting in top of it as fuel will float on water being lighter than water.

That's why water in fuel can cause huge problems as fuel tank pickups are located at the bottom of fuel tanks and the fuel pump will be pulling through water instead of fuel as the lighter fuel will be floating on top.

Thanks for taking the time to read this post as I know there's a few guys like me running around with old school outboards and hopefully this gives someone the insight in what to watch out for or maybe give it a go to fix it themselves.

Cheers.

[SquidMarks]

Loving your work Fab!

I know it takes a lot of effort writing these up (having to stop every so often to take pictures) so i really do appreciate it!

[Fab1]

Loving your work Fab!

I know it takes a lot of effort writing these up (having to stop every so often to take pictures) so i really do appreciate it!

Anytime mate.