Fuel line leaks

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Graham_Wright

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Gloucestershire
www.mastaclimba.com
Mine is a 1500 BMC diesel which is reluctant to start. Once running, it is fine.

Cracking the connection to one of the injectors shows foam implying air in the system.

There is a lift pump from the tank to the first trap/filter above the engine. Then to the second filter just below and then to the engine pump. The inlet to the engine pump is free flowing. I can find no obvious leaks between the engine pump and the injectors.

Any tips please on tracing?

Transparent hoses would help but sound dodgy.
 
Hardened copper washers in banjo joints? Perished flexible pipes? Corroded metal pipes? Loose joints? Not necessarily in that order.
 
If you have air in the system then it is usually introduced on the suction end of the fuel system not the pressure end. You have looked for pressure leaks but have you looked for suction leaks ?
 
Davegriff said:
Hardened copper washers in banjo joints? Perished flexible pipes? Corroded metal pipes? Loose joints? Not necessarily in that order.
Click to expand...

he means re aneal all copper washers
check fuel pump filter which is on top of the pump, it could also be the none return valve in the lift pump

some of the 1.5's still have plastic fuel return hose between the injectors this stuff can crack

cheers
mick
 
theoldsalt said:
If you have air in the system then it is usually introduced on the suction end of the fuel system not the pressure end. You have looked for pressure leaks but have you looked for suction leaks ?
Click to expand...

Yes. I assumed (and understand) that air is unlikely to be admitted after the injector pump.
Is there any mileage in applying something around the various joints (a bit like washing up liquid looking for escaping air but in reverse)?

Diagnosis is the problem as access is poor. I can strip all the pipe work and redo each connection but it would be nice to know what was causing the problem.

She is on the hard and it is great to see the prop turning after all these years (don't ask!). (And yes, the Deep Sea seal and cutlass are lubricated with exhaust water before anyone chides!).
 
If she's not been used for years, perished pipe work may be trouble. If you can clean off all pip work etc and pressurized system somehow, you may see a leak. The gasket around the top of the lift pump may have hardened. Sorry, I don't know of any quick easy way to do the job. Hopefully someone will be along soon who does.
 
Davegriff said:
If she's not been used for years, perished pipe work may be trouble. If you can clean off all pip work etc and pressurized system somehow, you may see a leak. The gasket around the top of the lift pump may have hardened. Sorry, I don't know of any quick easy way to do the job. Hopefully someone will be along soon who does.
Click to expand...

Great! Of course, I can pressurise the system with air and look for bubbles - easy - thanks!
 
If you spray the joins with shaving foam you will soon find any leaks, a temporary clear pipe on the return will show you how big the problem is with it running.
 
I've mentioned this many times put talcum powder (not shaving foam) on all the joints, as air is sucked in diesel is let out. Run the engine for five minutes, leave it ten minutes and if there are leaks you will see them in the powder.
 
>as air is sucked in diesel is let out...
>>How does that work then?

Diesel will go through a microscopic hole that you can't see, anything slightly bigger will let air in and diesel out. If you think about it the fuel system is sucking fuel into the engine thus air can be sucked in and because the pressure outside the fitting is less than the pressure that the diesel is in it seeps out even a tiny hole.Talcum powder can be used to find microscopic holes in welds, paint diesel on one side and put talcum powder on the other side.
 
KellysEye said:
>as air is sucked in diesel is let out...
>>How does that work then?

Diesel will go through a microscopic hole that you can't see, anything slightly bigger will let air in and diesel out. If you think about it the fuel system is sucking fuel into the engine thus air can be sucked in and because the pressure outside the fitting is less than the pressure that the diesel is in it seeps out even a tiny hole.
Click to expand...

Absolute rubbish - in systems under suction, diesel does not leak out, and sprinkling talcum powder everywhere will simply make a mess.
 
pvb said:
Absolute rubbish - in systems under suction, diesel does not leak out, and sprinkling talcum powder everywhere will simply make a mess.
Click to expand...

Also s-foam will be dissolved by the slightest whiff of diesel indicating where a leak is, the rest can be rinsed off? but I've only been doing engines for 35 years so what would I know!?
 
mtb said:
he means re aneal all copper washers
check fuel pump filter which is on top of the pump, it could also be the none return valve in the lift pump

some of the 1.5's still have plastic fuel return hose between the injectors this stuff can crack

cheers
mick
Click to expand...

……yes and this return hose returns to the filter not the tank. I can try disconnecting that and blanking the connection.
 
Graham_Wright said:
..........................Transparent hoses would help but sound dodgy.
Click to expand...

I have a transparent hose between the primary CAV filter and the lift pump.
I've become accustomed to seeing a large amount of air here. (in particular if the engine hadn't been running for some days).
Never gave me any starting or running problems, the air bubble would clear itself upon startup.

I always assumed this air got shunted back to the tank via the fuel return line at the secondary filter, while the return lines at the injectors return fuel only.

I have never read anywhere about my bukh 20 being a self-bleeding design, but it's been my experience (or perhaps just my assumption) that having two fuel return paths makes it so (one between the lift and injector pump i.e. on the secondary filter, & one from the injectors).

Just an observation for whatever it may be worth.

edit: as an afterthought, the above isn't worth a whole lot without giving a description of my engines fuel delivery setup. it differs somewhat from your own if I'm reading correctly.

Fuel delivery line from the tank - to primary filter - to engine lift pump is gravity fed.
Fuel delivery from lift pump - to secondary filter - to injector pump - to injectors is pressurised (obviously).
The fuel return line daisy chains injector#1, injector#2, a bleed point atop the secondary filter housing, then back to the tank.

hopefully of more value.
 
Last edited:
Checked everything and nothing amiss found.

There is no emission form the injector bleed line which is interesting but continuous attempts to start eventually produced results. That was yesterday morning around 1000. I left it for a few hours and she started with no pre-heat and just a few ladylike coughs and splutters. This morning, after a cold night, 20 seconds of preheat and off she went gain. Still a few coughs and splutters though.

I guess I didn't clear the air thoroughly in the first place.

Should I expect something out of the bleed line?
 
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