Best way find a tiny air leak in diesel engine?

[bizzard]

If it has a filter in it it should be retained by a bayonet fitting cap on the end, like a light bulb socket, push in a bit, twist about 1/4'', pull off.  Watch the spring doesn't jump out when removing it.

[Tony Brooks]

1 minute ago, Mike Adams said:

Can you hear the fuel pump ticking fast  when the ignition is on and the engine not running? You should also hear fuel going back into the tank. They can still run without the fuel pump if it gravity fed which can give rise to this sort of problem.

good point - even open a return pipe connection and turn the ignition on - direct output into a jar or something.

1 minute ago, bizzard said:

If it has a filter in it it should be retained by a bayonet fitting cap on the end, like a light bulb socket, push in a bit, twist about 1/4'', pull off.  Watch the spring doesn't jump out when removing it.

I think the Isuzu electric pumps are bolted to the engine and are nothing like the one you describe but I might be wrong.

[bizzard]

47 minutes ago, Tony Brooks said:

good point - even open a return pipe connection and turn the ignition on - direct output into a jar or something.

I think the Isuzu electric pumps are bolted to the engine and are nothing like the one you describe but I might be wrong.

Yes generally fitted to Vetus or Thornycroft Mitsubishi marinizations, but I just remember coming across one on an old Isuzu 45 in an ex Black Prince boat, probably a replacement for a faulty Isuzu built in one.

[Tony Brooks]

32 minutes ago, bizzard said:

Yes generally fitted to Vetus or Thornycroft Mitsubishi marinizations, but I just remember coming across one on an old Isuzu 45 in an ex Black Prince boat, probably a replacement for a faulty Isuzu built in one.

 

Could well be, the well now breakdown company sometimes fit electric pumps when the one on the engine fails.

[ditchcrawler]

On 13/09/2020 at 07:21, canalboat77 said:

The engine is an Isuzu 35 see attached pic I took last night. Thanks again everyone. 

If it is air entering the fuel system I would put my money on that filter below the calorifier, its probably the point of highest Vacuum and drawing in around the rubber filter seals.

[Tony Brooks]

1 hour ago, ditchcrawler said:

If it is air entering the fuel system I would put my money on that filter below the calorifier, its probably the point of highest Vacuum and drawing in around the rubber filter seals.

Agreed, especially as its a pattern filter.

[Bod]

Now I know that the engine would have to be running for this to be tried.

A length of pipe (6mm dia) one end held close to the ear, the other moved around very close to each joint, listening for the sound of any sucking, or blowing.

Would an air leak into a fuel pipe make enough noise to allow it to be found?

I know this method works well on pressured air lines.

Or am I woofing up the wrong birds nest support system?

 

Bod.

[Bee]

Those yellow hose fuel lines don't seem to have  jubilee clips or anything on them. Am I right or are they swaged fittings? (might have the wrong word there)

[dmr]

I have had some recent big air in fuel issues, still not completely fixed.

The air leak will be tiny so will not be found with an improvised stethoscope.

I fitted a cheap vacuum gauge to a spare filter port, closed the cock at the tank and hand primed the lift pump to create a vacuum. I reckoned it would be easier to find the leak like this than with the engine running. I even tried to submerge the entire first filter in a pot of diesel.

In my case it turned out that I did not have a leak but that under certain circumstances there was enough flow and vacuum to suck the dissolved air out of the diesel. I believe this is why some engines like BMC have a drain-back via a little orifice from the filter top.

After bleeding out the air I would have to run my engine for at least a couple of hours before there enough air to cause trouble.

 

...............Dave

[Tony Brooks]

8 minutes ago, Bee said:

Those yellow hose fuel lines don't seem to have  jubilee clips or anything on them. Am I right or are they swaged fittings? (might have the wrong word there)

 

The ones at the engine end seem to have swage sleeves, cant see if they have been swaged but one sees of lesser diameter than the hose so probably has.